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UBC Theses and Dissertations

Food and trophic relationships of the developmental stages of marine copepods Euchaeta japonica marukawa… Pandyan, Anna Soundram 1971

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FOOD AND TROPHIC RELATIONSHIPS OF THE DEVELOPMENTAL STAGES OF MARINE COPEPODS EUCHAETA JAPONICA MARUKAWA AND CALANUS PLUMCHRUS MARUKAWA BY ANNA SOUNDRAM PANDYAN A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSPHY in the Department of ZOOLOGY and INSTITUTE OF OCEANOGRAPHY We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA March, 1971 i i i In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y a v a i l a b l e for reference and study. I further agree that permission f o r extensive copying of t h i s thesis for s c h olarly purposes may be granted by the Head of my Department or by h i s representatives. It i s understood that copying or p u b l i c a t i o n of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department The University of B r i t i s h Columbia Vancouver 8, B. C., Canada Date i Chairman: Dr. A. G. Lewis ABSTRACT Studies of feeding of the l i f e history stages of marine copepods Euchaeta japonica Marukawa and Calanus plumchrus Marukawa suggest that the f i r s t two naupliar stages of both species are non-feeding stages. Feeding starts with the th i r d nauplius i n both species. These and l a t e r stages feed readily on h e a t - k i l l e d , f l a g e l l a t e s Dunaliella t e r t i o l e c t a . The f i f t h and six t h n a u p l i i of japonica and the fourth nauplius of Cj_ plumchrus also feed on large diatoms; they were fed Ditylum b r i g h t w e l l i i and Chaetoceros  serpentrionalis, respectively. The si x t h nauplius of both species, given a mixture of phytoplankton and zooplankton, feeds s e l e c t i v e l y on D. t e r t i o l e c t a . In japonica copepodite stages one to s i x (female and male) are omnivorous, but food s e l e c t i v i t y experiments suggest that copepodite stages one to s i x (female) are primarily carnivorous, whereas males (stage six) are primarily herbivorous. This difference i n feeding habits accords with the morphology of the mouthparts. In C\_ plumchrus copepodites one to s i x (female) are morphologically adapted for a herbivorous d i e t , but copepodites three to six (female) are capable of feeding on zooplankton also. Copepodite stages three and f i v e prefer zooplankton, whereas the older and younger stages prefer phytoplankton. Preference for the large-sized phytoplankton has been indicated i n the feeding of copepodite stages of C_;_ plumchrus both i n a mixture of foods and i n unialgal cultures. Temporal v a r i a t i o n i n feeding i s conspicuous i n copepodite stages of C. plumchrus, and i s related to d i e l v e r t i c a l d i s t r i b u t i o n and a v a i l a b i l i t y of food. Copepodite stages of E. japonica show less pronounced temporal v a r i a t i o n , and their feeding does not seem to be closely related to the i r i i v e r t i c a l d i s t r i b u t i o n . The quantity of food consumed by developmental stages of both species i n the laboratory when compared with that available i n the sea, suggests that the potential capacity for feeding by these animals i s not usually reached i n the sea. i v TABLE OF CONTENTS Page Abstract i CHAPTER I INTRODUCTION 1 CHAPTER I I MATERIALS AND METHODS 5 Fi e l d collections 6 Area of study 6 Laboratory studies 9 Studies on grazing 9 Culture technique 15 Studies on predation 15 Studies on food selection 16 Studies on the seasonal v a r i a t i o n i n the feeding of the C/2 and C/6 - female of lE^ japonica and C/5 Cj_ plumchrus 18 Fi e l d studies 18 Determination of d i e l v e r t i c a l d i s t r i -bution of the developmental stages of E. j aponica and C^ plumchrus 18 • Trophic relationships of the develop-mental stages of E^ japonica and C. plumchrus 19 CHAPTER I I I RESULTS 21 Morphology of the feeding appendages of E^ j aponica and C^ plumchrus 21 Laboratory feeding experiments of the naupliar stages of Euchaeta japonica 22 Laboratory feeding experiments of the naupliar stages of Calanus plumchrus 23 Laboratory grazing experiments with the copepodite stages of E^ j aponica 23 Laboratory grazing experiments of the copepodite stages of Cj_ plumchrus 24 Laboratory predation experiments of the developmental stages of E^ japonica .. 26 Laboratory predation experiments of the developmental stages of C_^  plumchrus.. 33 V Page Laboratory predation experiments of the C/5 stage copepodite. of japonica and plumchrus 33 Experiments on the food s e l e c t i v i t y of the developmental stages of E. japonica .. 33 Experiments on the food s e l e c t i v i t y of the developmental stages of C. plumchrus 37 Experiments on the seasonal v a r i a t i o n i n the feeding of the C/2 and the C/6 -female of E. japonica 41 Experiments on the seasonal va r i a t i o n i n the feeding of the C/5 stage of C. plumchrus 42 Results of f i e l d observations 42 Temporal v a r i a t i o n i n the feeding of the copepodite stages of Ej_ j aponica 42 Temporal v a r i a t i o n i n the feeding of the copepodite stages of plumchrus .... 44 Qualitative gut analysis 45 Di e l v e r t i c a l d i s t r i b u t i o n of the developmental stages of E^ japonica 50 Die l v e r t i c a l d i s t r i b u t i o n of the developmental stages of C. plumchrus ..... 52 Estimation of particulate matter in the near surface and near deep water i n Howe Sound during different seasons of the year 55 CHAPTER IV • DISCUSSION OF RESULTS 58 CHAPTER V SUMMARY AND CONCLUSIONS 73 BIBLIOGRAPHY 76 APPENDIX A Morphology of the developmental stages of j aponica Marukawa and C. plumchrus Marukawa 102 Terminology 103 Description 103 Morphology of the developmental stages of E. japonica 103 v i Page Morphology of the developmental stages of Cj_ plumchrus 117 APPENDIX B Raw Data 131 APPENDIX C Tables and figures of phytoplankton and zooplankton species used i n the laboratory feeding experiments 181 v i i LIST OF TABLES APPENDIX B Table Page 1. Feeding experiments with the naupliar stages of Euchaeta japonica Marukawa 131 2. . Feeding experiments with the naupliar stages of Calanus plumchrus Marukawa 133 3. Grazing experiments of the copepodite stages of E. j aponica 135 4. Grazing experiments of the copepodite stages of C. plumchrus 137 5. Predation experiments of the developmental stages of E^ j aponica on the f i r s t day Artemia n a u p l i i 140 6. Predation experiments of the copepodite stages of E ^ j aponica on the f i f t h day Artemia n a u p l i i 141 7. Predation experiments of the copepodites of E. j aponica on the second day Artemia n a u p l i i 142 8. Predation experiments of the copepodites of E ^ japonica on Tigriopus c a l i f o r n i c u s 142 9. Predation experiments of the copepodite stages of E. japonica on 'Various zooplankton 143 10. Predation experiments of the male and female copepodite stages V and VI of E ^ japonica on f i r s t day Artemia n a u p l i i 144 11. Predation experiments of the developmental stages of C. plumchrus on f i r s t day Artemia n a u p l i i 145 12. Selective feeding experiments of the s i x t h nauplius of E ^ j aponica 146 13. Selective feeding experiments of the f i r s t copepodite stage of j aponica 147 14. Selective feeding experiments of the second copepodite stage of E ^ japonica 149 15. Selective feeding experiments of the t h i r d copepodite stage of E ^ j aponica 150 16. Selective feeding experiments of the fourth copepodite stage of E ^ j aponica 151 v i i i LIST OF TABLES APPENDIX B Table Page 17.. S e l e c t i v e feeding experiments of the f i f t h copepodite stage of Ej_ japonica 152 18. S e l e c t i v e feeding experiments of the s i x t h copepodite stage (female) of E. japonica. 153 19. S e l e c t i v e feeding experiments of the s i x t h copepodite stage (male) of E. japonica 155 20. S e l e c t i v e feeding experiments of the copepodite stages of E^ _ j aponica 156 21. The r e s u l t s of the a n a l y s i s of variance of four v a r i a b l e s of concentration of the prey (C), s i z e of the prey (S), developmental stage of the predator (D), and the number of r e p l i c a t i o n s (R) 158 , 22. S e l e c t i v e feeding experiments of the s i x t h nauplius of plumchrus 160 23. S e l e c t i v e feeding experiments of the f i r s t copepodite stage of plumchrus 1.61 24. S e l e c t i v e feeding experiments of the second copepodite stage of C. plumchrus 162 s 2 5 i ; S e l e c t i v e feeding experiments of the t h i r d copepodite- stage- of plumchrus 163 26.. S e l e c t i v e feeding experiments of the fourth copepodite stage of C. plumchrus 164 .27. S e l e c t i v e feeding experiments of the f i f t h copepodite stage of C. plumchrus 165 28. S e l e c t i v e feeding experiments of the, s i x t h copepodite stage of C. plumchrus 166 29. Results obtained when a mixture of v a r i o u s -sized• Q^^M^ll^ ^E^lsl^S^. was of f e r e d to the* copepodite stages of plumchrus. Data are presented as percent eaten of the a v a i l -able volume of food 167 30*. Results obtained when a mixture of v a r i o u s -siz e d Chaetoceros chains was o f f e r e d to the copepodite stages of plumchrus. Data are presented as percent eaten of the a v a i l a b l e volume of food 169 i x LIST OF TABLES APPENDIX B Table Page 31. Results obtained when a mixture of various-sized Ditylum b r i g h t w e l l i i was offered to the copepodite stages of C. plumchrus. Data are presented as percent eaten of the a v a i l -able volume of food 171 32. Predation experimental results of the second and si x t h (female) copepodite stages of E. j aponica i n the summer and f a l l 173 33. Grazing experiments of the copepodite f i v e of C. plumchrus i n the summer 174 34. Grazing experiments of the copepodite f i v e of C. plumchrus i n the f a l l 175 35. Selective feeding experiments of the copepodite f i v e of plumchrus i n the summer 175 36. Seasonal and dai l y v a r i a t i o n i n feeding of the copepodite stages of E. japonica and C. plumchrus expressed i n percentage of the number of animals examined .176 37. Total volume of particulate matter available i n different seasons at various depths i n Howe Sound, B.C. 179 APPENDIX C Phytoplankton species used for the graz experiments i n the laboratory Zooplankton species used for predation experiments i n the laboratory x i LIST OF FIGURES Figure Page I Chart of Howe Sound waters showing p o s i t i o n s of S t a t i o n s 1 and 2, from which the developmental stages of E. j aponica and plumchrus were c o l l e c t e d 5 I I Van dorn b o t t l e (water sampler) 7 I I I Percentage of a v a i l a b l e D u n a l i e l l a  t e r t i o l e c t a and Ditylum b r i g h t w e l l i i eaten by the copepodite stages of C. plumchrus 25 IV Mean feeding r a t e s of the C/l stage of E_. j a p o n i c a i n d i f f e r e n t c o n c e n t r a t i o n s of. f i r s t day and f i f t h day Artemia n a u p l i i 28 V Mean feeding r a t e s of the, C/4 and C/5 stages of - Ej_ j a p o n i c a i n d i f f e r e n t c o n c e n t r a t i o n s of T i g r i o p u s c a l i f o r n i c u s ........ 29 VI Mean feeding r a t e s of the C/5 - female and C/5 - male of E. j a p o n i c a i n d i f f e r e n t c o n c e n t r a t i o n s of f i r s t day Artemia n a u p l i i ...... 30 V I I Mean' feeding r a t e s of the C/6 - female and G/6 - male of E. 1aponica i n d i f f e r e n t con-c e n t r a t i o n s o f f i r s t day Artemia n a u p l i i .: 30 VII X Mean, feeding r a t e s of the C/5 stage of E. j a p o n i c a and the. C/5 stage of plumchrus i n d i f f e r e n t ' c o n c e n t r a t i o n s of f i r s t day Artemia n a u p l i i 32 IX Mean feeding r a t e s o f the copepodite stage of E_^_ j a p o n i c a i n d i f f e r e n t c o n c e n t r a t i o n s of a mixed c u l t u r e o f f i r s t day and f i f t h Artemia n a u p l i i - — ( A ) to- (F) 35 X Mean, feeding r a t e s of the C/2 stage of E. j aponica i n d i f f e r e n t concentrations> of f i r s t day Artemia n a u p l i i i n the: summer and i n the f a l l 40 XI Mean fee d i n g r a t e s of the C/6 - female stage of E_j_ j a p o n i c a i n d i f f e r e n t c o n c e n t r a t i o n s of f i r s t day Artemia n a u p l i i i n the summer and i n the f a l l , 40 x i i Figure Page XII D i e l v e r t i c a l d i s t r i b u t i o n of the developmental stages of j aponica i n December, 1968 46 XIII D i e l v e r t i c a l d i s t r i b u t i o n of the developmental stages of j aponica in January, 1969 47 XIV D i e l v e r t i c a l d i s t r i b u t i o n of the developmental stages of E ^ j aponica in February, 1969 48 XV D i e l v e r t i c a l d i s t r i b u t i o n of the developmental stages of Ej_ j aponica i n March, 1969 49 XVI D i e l v e r t i c a l d i s t r i b u t i o n of two copepodite stages of plumchrus: The C/5 stage (December, 1968), the C/5 and C/6 - female (January, 1969) , and the C/6 - female (February, 1969) . . . 52a XVII D i e l v e r t i c a l d i s t r i b u t i o n of the developmental stages of C_^_ plumchrus in March, 1969 53 XVIII Concentrations of organic p a r t i c l e s i n the water samples taken from 230 m. depth i n the winter (December, 1968) 54 XIX Concentrations of organic p a r t i c l e s i n the water samples taken from near-surface (100 m.) and near-bottom (230 m.) of Howe Sound, i n March, 1969 56 x i i i APPENDIX A  LIST OF FIGURES Figure Page 1. Naupliar stages of Ej_ japonica 79 2. F i r s t antennae of the naupliar stages of E^ j aponica 80 3. Second antennae of the naupliar stages of E^ japonica 81 4. Mandibles of the naupliar stages of E. japonica 82 5. Copepodite stages of E. japonica 83 6. F i r s t antennae of the copepodites of E^ _ j aponica. 84 7. Second antennae of the copepodites of E. japonica 85 8. Mandibles of the copepodites of E. japonica 86 9. F i r s t maxillae of the copepodite stages of E. japonica 87 10. Second maxillae of the copepodite stages of E. j aponica . .. 88 11. Maxillipeds of the copepodite stages of E. j aponica 89 12. Naupliar stages of C. plumchrus 90 13. F i r s t antennae of the naupliar stages of C^ plumchrus 91 14. Second antennae of the naupliar stages of Cj_ plumchrus 92 15. Mandibles of the naupliar stages of C. plumchrus 93 16. F i r s t maxilla of the f i f t h nauplius of C. plumchrus 94 17. Copepodite stages of Calanus plumchrus 95 18. F i r s t antennae of the copepodite stages of C_^_ plumchrus 96 x i v APPENDIX A  LIST OF FIGURES Figure Page 19. Second antennae of the copepodite stages of plumchrus 97 20. Mandibles of the copepodite stages of C. plumchrus 98 21. F i r s t maxillae of the copepodite stages of C_^_ plumchrus 99 22. Second maxillae of the copepodite stages of C^_ plumchrus 100 23. Maxillipeds of the copepodite stages of C. plumchrus 101 APPENDIX C  LIST OF FIGURES 1. Dunaliella t e r t i o l e c t a 183 2. Phaeodactylum tricornutum 183 3. Ditylum b r i g h t w e l l i i 184 4. Chaetoceros serpentrionalis 185 5. A. Coscinodiscus concinnus - surface view 186 B. Coscinodiscus concinnus - l a t e r a l view 186 6. Thalassiosira r o t u l a 187 7. Skeletonema costatum 188 8. Nitzschia sp 188 9. F i r s t day Artemia nauplius 189 10. F i f t h day Artemia nauplius 189 11. Barnacle nauplius 190 12. Tigriopus cali f o r n i c u s 190 13. Oncaea borealis 190 XV APPENDIX C LIST OF FIGURES Figure Page 14. and 15. Crustacean remains from the guts of the copepodites of E. j aponica 191 16. Remains of Coscinodiscus sp. from the guts of the copepodite stages of Cj_ plumchrus 192 17. Remains of Ditylum b r i g h t w e l l i i from the guts of the copepodite stages of C. plumchrus 192 18. Isochrysis galbana 193 x v i ACKNOWLEDGMENTS To ray research advisor, Dr. A. G. Lewis, for h i s guidance, advice and c r i t i c i s m , to Dr. P. A. Larkin, Dr. D. C h i t t y , Dr. J . E. P h i l l i p s and Dr. F. J . R. Taylor, f o r t h e i r valuable suggestions and generous help, to Dr. M. M. M u l l i n , my external examiner f o r h i s u s e f u l and rewarding sug-gestions given at the i n i t i a l stages of my research work, -to my f r i e n d , Dr. P. Raghunathan, f o r h i s constant help, advice and encourage-ment during the research and f o r h i s time and whole-hearted e f f o r t i n the preparation of t h i s t h e s i s , to my f r i e n d s , Dr. E. S. G i l f i l l a n , Mr. Richard Pieper and Miss Marlene Evans, for t h e i r valuable help, to Mrs. Margaret Jensen and Mr. K. R. Rajagopalan f o r t h e i r help with some of the i l l u s t r a t i o n s , to Mrs. S. Morton f o r the typing of my thesis i n a short time, to the o f f i c e r s and men of CNAV Laymore, CNAV Endeavour, EtSohli, and CSS Vector, for t h e i r cheerful assistance i n the gathering of the data, and to a l l my friends at the I n s t i t u t e of Oceanography f o r th e i r generous help throughout t h i s work. x v i i T O T H E M E M O R Y 0 F M Y B E L O V E D A U N T MISS HILDA JESUDIAN 1 CHAPTER I INTRODUCTION Copepods are present i n the sea i n great numbers, dominating the zooplankton and forming one of the stable constituents i n the ocean. They form a p r i n c i p a l food source for fishes and whales. Order Copepoda includes herbivores which feed on phytoplankton, carnivores which feed on zooplankton, and omnivores which feed on both. In addition, some copepods are detritus feeders. Thus, these animals play an important role i n the marine food chain. A food chain i s a series of organisms, each of which devours, the next i n the series as i t s p r i n c i p a l food source (Simpson and Beck, 1965). Each successive l e v e l of nourishment, as represented by the l i n k s of the food chain, i s known as a trophic l e v e l . Thus, i n general, the phytoplankton which synthesizes organic matter constitutes the f i r s t trophic l e v e l , the herbivores which feed on the phytoplankton form the second trophic l e v e l , and the ca r n i -vores which feed on zooplankton represent the th i r d trophic l e v e l . I t i s not uncommon for a species to belong to more than one l e v e l , as i n the case of the omnivores; sometimes a species changes i t s diet to a considerable extent, depending on the a v a i l a b i l i t y of food. Thus, the assignment of the marine copepods to different trophic levels may be d i f f i c u l t . The calanoid copepods Euchaeta japonica Marukawa and Calanus plumchrus Marukawa are important members of the zooplankton i n the coastal waters of B r i t i s h Columbia. Euchaeta j aponica i s present i n small numbers throughout the year while Calanus plumchrus i s present i n large numbers i n the spring. Adult female E. japonica are primarily carnivorous; adult female C. plumchrus are primarily herbivorous. Consequently, they occupy different trophic levels i n the food chain. I t was therefore thought that a study of the food and feeding of the stages i n the l i f e h istory of these two species could shed some 2 l i g h t on the complex in t e r - r e l a t i o n s of copepods i n the food chain. I t should be mentioned here that the l i f e h istory of both E.japonica and Cj_ plumchrus comprises six naupliar stages succeeded by s i x copepodite stages. The naupliar stages s h a l l be referred to i n t h i s study by the abbreviated notation N/1 to N/6, and the copepodite stages denoted by C/l to C/6. Four methods of studying feeding and feeding rates of copepods have been suggested by M u l l i n (1966). The f i r s t of these i s the study of mouthparts, which may indicate how the parts are adapted to handle the food and, therefore, the general type of food the copepod can eat. This relationship to feeding and the mouthparts i s i l l u s t r a t e d i n the work of Anraku and Omori (1963). They observed that Calanus finmarchicus Gunnerus was primarily a herbivore (feeding experiments) and that some of i t s mouthparts were capable of producing currents which concentrated food organisms while other mouthparts were pro-vided with grinding teeth to break up the food. These authors also examined the feeding of the predatory copepod Tortanus discaudatus. I t was found to have prehensile appendages and sharp teeth on the mandibles, which presumably were used for grasping and tearing apart prey organisms. There i s also experi-mental evidence that a copepod adapted for grazing may also have the cap a b i l i t y of feeding on animal food, and that a carnivore may be able to feed on plant food (Mullin, 1966). Therefore, inferences regarding food habits cannot be conclusive i f they are based on the observations of mouthparts alone. The second of the four methods i s an examination of the gut-content of animals taken from the f i e l d . The gut-content of animals captured at different periods of the day from various depths of the ocean would indicate the composi-tion of food ingested near the time of capture and, therefore, the temporal variation i n feeding. Usually however, a majority of the animals from a catch have empty i n t e s t i n a l tracts (Conover 1960, Wickstead 1962, Arashkevich 1968). Also, naked f l a g e l l a t e s , bacteria, and animals with a soft body can seldom be 3 i d e n t i f i e d . Therefore, the food composition and consequently the feeding behaviour of the animal i s hard to estimate. The th i r d method i s to conduct feeding experiments on animals i n the laboratory. In these experiments, one type of food i s used at a time, and feeding rates are obtained i n ' d i f f e r e n t concentrations of the food. The feeding rates would indicate the extent to which the animal can feed on a single type of food i n the absence of others as well as the effect of different concentrations of t h i s food. However, the amount of food consumed depends on various factors such as the s i z e , sex, and age of the feeding animal, the si z e , shape, and concentration of the prey as well as on the duration of the -experiment (Mullin, 1963). The fourth method i s by the measurement of the feeding rates of animals fed on a mixture of various types of food i n the laboratory. S e l e c t i v i t y , i f present, for a s p e c i f i c type of food may be governed by the p a r t i c u l a r s i z e , _ shapes m o t i l i t y , taste, or chemical composition of the food p a r t i c l e . Selec-t i v i t y for p a r t i c u l a r sizes of prey has been shown by Harvey (1937) . He found that Galanus finmarchicus s e l e c t i v e l y fed on the diatom Ditylum b r i g h t w e l l i i from a mixture of Ditylum and Lauderia. Copepods of the families Calanidae and Eucalanidae also seem to prefer large p a r t i c l e s (Mullin, 1966). Thus, the feeding behaviour of a variety of adult or pre-adult copepods has been studied in the laboratory by several workers. Estimations of feeding are d i f f i c u l t to obtain i n the f i e l d . In spite of t h i s , a few f i e l d studies have been carried out. Parsons et a l . (1969) studied primary and secondary production and made observations on the food of l a r v a l and juvenile f i s h i n the Fraser River plume i n the S t r a i t of Georgia. The study revealed that, of the diatoms and microflagellates available, the diatom species Skeletonema  costatum, Thalassiosira nordanskioldii, and T\_ rotula were a l l grazed extensively. They appeared to be an excellent food source for the species of copepods present 4 under the Fraser River plume. The developmental stages nauplius 1 to 6, and copepodites 1, 3, and 5 of C. plumchrus are present between February and May. The grazing experiments on these developmental stages (Parsons et a l . , 1969) suggested that microflagellates are not a good source of food for the C/3 and C/4 stages. The diatom Skeletonema costatum was a better source of food for the C/3 and C/4 than for the C/5 stage. With the above background information i t was of interest i n this study to determine the nature of food-selection by the developmental stages of the nominally herbivorous copepod C_^_ plumchrus and the nominally carnivorous copepod j aponica. The purpose of th i s research was to conduct detailed experiments i n the laboratory, and to make gut-content analysis of the animals in the f i e l d to determine the quality and quantity of food required by the developmental stages of both copepods. The results of the study are also com-pared with the results of a study on the functional morphology of the mouth-parts of the developmental stages. The c a p a b i l i t i e s and requirements of the organisms as determined i n the laboratory were compared with the quantity of food available i n the f i e l d to determine the trophic relationships of the developmental stages. 5 Figure I. Chart of Howe Sound waters showing positions of stations 1 and 2, from which the developmental stages of E.japonica and C_. plumchrus were collected. 6 CHAPTER I I MATERIALS AND METHODS Fi e l d c o l l e c t i o n s : A general account i s given here of the procedures adopted for f i e l d c o l l e c t i o n s . Specific materials and methods used i n different aspects of this work are described i n each of the sections of th i s chapter. Area of study: Howe Sound, an i n l e t near Vancouver, B r i t i s h Columbia (Fig. 1), was chosen as the study area because of the occurrence there of both species of copepods, the proximity of the study area to Vancouver, and the existence of previous studies on the physical oceanography of the i n l e t (Pickard, 1961). The i n l e t has a length of 23 nautical miles, a mean depth of 225 metres and a mean annual fresh water discharge of 460 cubic metres per second (Pickard, 1961). The animals for the morphological study were collected from two stations i n Howe Sound (Fig. 1). Station 1 (depth of 232 m) i s located at 49°20.5" N, 123 20.5" W, while Station 2 (depth of 234 m) i s located at 49 24.1" N, 123 18.1" W. Adult males and females of Euchaeta j aponica,and Calanus plumchrus were collected with a one metre diameter ring net (23 meshes per inch, mesh aperture approximately 0.7 mm square). The eggs and the C/3 to C/5 of E^ j aponica and the C/l to C/5 of Cj_ plumchrus were collected by a 70 cm diameter net (68 meshes per inch, mesh aperture approximately 0.23 mm x 0.21 mm). Both nets were hauled v e r t i c a l l y from 225m. to the surface. The other developmental stages of the two species were obtained from animals raised i n the laboratory. The specimens were then preserved i n 5% buffered formalin. The naupliar stages were stained with Lugol's solution and examined i n glycerine on depression s l i d e s . Whole mounts of the copepodite stages, as well as slides of the appendages of the naupliar and the copepodite stages, 7 Figure I I . Van Dorn bo t t l e fift 11 8 were either made i n Turtox CMC-S mixed with an equal amount of CMC-10 mounting medium or were cleared i n l a c t i c acid, stained i n Chlorazol Black E, and mounted i n glycerine. Drawings were made using a camera lucida. Sea water, for laboratory studies, was collected either with a 1 6 - l i t r e Van Dorn bottle (Fig. II) or with a 9 6 - l i t r e large volume sampler (Lewis, unpublished). Water was f i l t e r e d through a 0.45-micron m i l l i p o r e f i l t e r into 5-gallon polyethylene carboys and l a t e r stored at 8°C i n a cold room at the laboratory. Animals for laboratory study were collected i n a manner sim i l a r to that for the morphological study. The various l i f e h istory stages of E^ j aponica and plumchrus were picked up by glass pipettes from the net hauls and transferred to thermos flasks which had been f i l l e d with cold sea water collected e a r l i e r . The specimens, after being taken to the laboratory, were transferred to 4 - l i t r e beakers containing m i l l i p o r e f i l t e r e d (0.45 micron) sea water and maintained at 8°C i n the cold room. The egg clusters of E^ _ japonica , were placed i n large finger bowls wrapped i n aluminum f o i l to keep them i n the dark (survival was found to be better i n darkness). In the case of C. plumchrus, the groups of ind i v i d u a l eggs were kept i n 4 - l i t r e beakers wrapped i n aluminum f o i l . The naupliar stages and the f i r s t two copepodite stages of E. japonica were reared i n the laboratory using an enrichment solution (CEM/1 of Lewis, 1967) i n addition to food organisms. In the case of C. plumchrus, there was no difference i n t h e i r survival either with or without the enrichment, and therefore the naupliar and the f i r s t copepodite stages were reared without the enrichment solution. The remainder of the developmental stages of both species could not be reared i n the laboratory and were obtained from the f i e l d . For experiments on the f i r s t copepodite stage of plumchrus, experimental animals were obtained from the f i e l d i n addition to those reared i n the labora-9 tory. These animals are designated as C/l (Field) and C/l (Laboratory). The experimental feeding tests were run on a l l the developmental stages of the two species using both l o c a l and exotic food types (Table A of Appendix C) to obtain q u a l i t a t i v e and quantitative estimates of food consumption. Laboratory Studies Studies on grazing: The containers used for the feeding experiments were either 50-ml. Stender dishes, or 100-, 400-, or 600- ml. j a r s . The larger containers were used wherever possible to enable a large number of experimental animals to be used. In each of the grazing experiments there were four experimental tests and two controls. The experimental containers consisted of both food and feeding animals, whereas the controls consisted of food alone. The controls provided an indication of the changes that took place during the experiment other than those due to feeding. Starvation of the animals reduces the v a r i -a b i l i t y i n the feeding behaviour of the animals (Marshall, 1955a). Therefore the experimental animals were starved for twenty-four hours just prior to the experiment i n order to clear the alimentary t r a c t . A further discussion of the a p p l i c a b i l i t y of the technique of starvation w i l l be made i n Chaper IV. The phytoplankton culture which was to be used as food was kept i n the dark for twenty-four hours to allow the completion of any c e l l divisions that had already started and to reduce further r e p l i c a t i o n of c e l l s p r ior to the experiment. Because i t was found that a starved animal took approximately four to ten hours (with an average of six hours) to form a faecal p e l l e t , the experiments were run for seven to fourteen hours (with an average of nine hours). The quantity of food consumed by the experimental animals was deter-mined using Model B Coulter Counter. The operation of t h i s instrument may be 10 described as follows (Sheldon and Parsons, 1967). The Coulter Counter maintains an e l e c t r i c a l f i e l d across an aperture. As p a r t i c l e s pass through the aperture, they displace an equal volume of water, thereby causing a change i n the e l e c t r i c a l resistance. This change i s measured and d i g i t i z e d automatically on the counter. There i s thus a l i n e a r relationship between the p a r t i c l e volume and the e l e c t r i c a l pulses. The average volume of the p a r t i c l e s to be counted was determined by measuring the length and width of 150 to 200 p a r t i c l e s with an ocular micrometer. This allows the i d e n t i f i -cation of the appropriate p a r t i c l e s on the display screen of the counter. The food p a r t i c l e s used d i f f e r r e d i n size and shape. Because of t h i s , i t was thought advisable to determine the volume and the dry weight of the food to provide a basis for comparing the quantity of food consumed. To estimate the dry weight of the phytoplankton used, a known concentration of phytoplankton was f i l t e r e d through a 0.45-micron m i l l i p o r e f i l t e r of known weight. After the phytoplankton sample was f i l t e r e d , the f i l t e r was washed by passing approximately 10 ml. of d i s t i l l e d water through i t . The f i l t e r , with the phytoplankton, was dried on a p l a s t i c dish of known weight i n a vacuum desiccator on anhydrous copper sulphate for an hour and then further dried for seven hours i n a V i r t i s Unitrap 'Freeze Dryer' (model no. 10 - 100). The weight of the phytoplankton was determined with a 'Mettler' balance (Type 16). To determine the dry weight of zooplankton prey and feeding animals they were washed i n a clean, dry, preweighed, p l a s t i c dish. The water adhering to the body surface was blotted off with an absorbent tissue. The rest of the procedure for drying and weighing was the same as that for the phytoplankton. Low feeding rates of the n a u p l i i and the presence of some c e l l d i v i s i o n using l i v e c e l l s of Dunaliella t e r t i o l e c t a prevented the accurate determination of changes i n numbers of prey organisms due to feeding i n naupliar 11 stages. Therefore, in, experiments with a small number of n a u p l i i , heat-k i l l e d Dunaliella was used as food. The duration of the above experiments was also l i m i t e d to one hour owing to the loss of c e l l s by adherence to the walls of the dishes. Just p r i o r to these experiments a 25-ml. aliquot of L\_ t e r t i o l e c t a i n a 100-mL. container was h e a t - k i l l e d i n a water bath. The aliquot was cooled and then shaken thoroughly. One m i l l i l i t r e was pipetted from the aliquot into each of two 250-ml. beakers and each of six Stender dishes (four experimental and two controls). The mixture was made up to 150 ml. i n the beakers and up to 10 ml. i n the Stender dishes by adding 0.45-micron-filtered sea water of known background counts. .(The d i l u t i o n to 150 ml. i n the beakers was necessary for the counts to be made with the Coulter Counter.) The n a u p l i i of a sp e c i f i c stage, from food-free water, were added to each of the four experimental dishes and incubated along with the two control dishes for an hour. The mean concentration C ( c e l l s per ml.) i n the two beakers was m determined by using the Coulter Counter. I t was assumed here that C would m also be the i n i t i a l concentration i n both the control and experimental Stender dishes. After incubation, the contents of the Stender dishes were transferred to beakers and the culture solution was then made up to 150 ml. The n a u p l i i were withdrawn, along with the minimum possible amount of water, using a pipette. The concentration of D. t e r t i o l e c t a c e l l s after feeding was then determined with the Coulter Counter. The background count of the sea water was subtracted from the mean value of the c e l l counts to reduce the error due to dust or other a r t i f a c t s . Using these methods of measurement, the following parameters were obtained. The variables t, and t„ stand for time 'before' and 'after' feeding Before Feeding: Parameter After Feeding: Parameter D e f i n i t i o n The mean of i n i t i a l c e l l counts from control dishes at the beginning of an experiment. The mean of i n i t i a l c e l l counts from experimental dishes at the beginning of an experiment. D e f i n i t i o n £ The mean of c e l l counts from control dishes at the end of the experiment. The mean of c e l l counts from experi-E mental dishes at the end of the experi-ment . In view of the assumption made e a r l i e r (p. l l ) , i t i s seen that: m C t " E t 1 1 The loss i n the controls at the end of the experiment i s : L = C - C , z2 1 and the loss i n the experimental dishes, i e . due to feeding, i s : L2 L2 Therefore, the feeding rate (R), expressed as the number of c e l l s eaten per day per animal, i s : F N ( t 2 - t p x 24 .... (1) where N stands for the number of n a u p l i i and - denotes the duration of the experiment i n hours. 13 When the naupliar stages of both species were abundant, l i v e phyto-plankton of various sizes and large containers of 100-, 400-, and 600-ml. capacity were used. In these experiments a large number of n a u p l i i was used to obtain more e a s i l y detectable differences between the i n i t i a l and f i n a l counts. A 2-gallon polyethylene carboy was f i l l e d with the required amount of f i l t e r e d sea water, of known background count, and a desired quantity of phytoplankton was added to i t . This food mixture was distributed equally to six p l a s t i c containers of 400- or 600-ml. capacity, which were wrapped either i n black e l e c t r i c a l tape or i n aluminum f o i l . These containers (2 controls and 4 experimentals) were shaken thoroughly, a subsample of 200 ml. was taken from each, and the concentration of c e l l s before feeding was estimated with the Coulter Counter. An equal number of n a u p l i i was transferred to the experi-mental containers. A l l the containers were closed with p l a s t i c screw l i d s or with aluminum f o i l to reduce evaporation of water and were placed i n a model T.C. 5 'Rollordrum' (New Brunswick S c i e n t i f i c Co., Inc., New Jersey)* rotating at 1 r.p.m. During the 7 to 14 hour period of incubation, the movement of, the containers allowed more even d i s t r i b u t i o n of the food and the n a u p l i i . After incubation the containers were emptied into finger bowls to observe the condition of the animals and to remove the faecal p e l l e t s from the sample. A subsample of 200 ml. was taken from each and the concentration of c e l l s after feeding was estimated with the Coulter counter. In the above experiments a correction factor G was estimated and introduced i n the i n i t i a l counts of the experimental containers because of the unavoidable reproduction of the phytoplankton c e l l s i n the containers. * The o r i g i n a l drum supplied by the manufacturer was replaced by one with si x holes of 3" and another one with six holes of 4.1" diameter. Also, the turntable platform was raised to an angle of 45°. This factor i s derived on the assumption that the c e l l s increased i n the experimentals at the same rate as the controls; i t does not account for any loss i n the dividing c e l l s that may arise due to feeding. The correction factory may be derived as follows: Increase i n the controls (due to reproduction)= C - C t2 t l To arrive at an approximation which represents the proportionate values of experimental dishes, (C - C ) i s divided by C , and th i s value i s 2 1 1 mult i p l i e d by the i n i t i a l experimental c e l l count. Thus: 5 t " 5 t 2 1 The correction factor (G) = - X E \ The corrected i n i t i a l experimental value (E ) = G + E . t t c 1 The loss i n the experimental dishes due to feeding (F) = E - E c 2 The feeding rate R = — , x 2Z> ^2 "™ 1 N ( t - t X 2 4> N^Z2 1) :i n units of number of c e l l s eaten/animal/day. In the above experiments, when chain forms of diatoms with a large c e l l size range were used as food, the number of food c e l l s of each size with-i n a species was counted with the Coulter Counter (Sheldon and Parsons, 1967, pp. 18 and 19). The procedure for the grazing experiment, as well as the e s t i -mation of the feeding rates adopted for the n a u p l i i , were also used for the copepodite stages of Ej_ japonica and C^ plumchrus. In a l l the above experiments the counts of food p a r t i c l e s from each container were subjected to s t a t i s t i c a l t - t e s t s . The mean, variance, standard deviation, and coeffic i e n t of va r i a t i o n for the mean of the i n i t i a l and f i n a l 15 counts of the replicates were computed. The above analyses of data were carried out on the IBM 7044, 7422, and 360 (model 67) computers. Culture technique: This technique also was adopted to detect feeding i n the naupliar stages. F i f t y to s i x t y n a u p l i i of each of the f i r s t three naupliar stages (N/1 to N/3) of E. japonica were exposed to high concentrations (50 - 70,000 cells/ml.) of Dunaliella sp. for a day. The n a u p l i i were then removed from the culture and washed i n f i l t e r e d sea water to remove any food p a r t i c l e s s t i c k i n g .to. the appendages and other parts of the body. The n a u p l i i were put in test tubes and were gently crushed i n a few drops of "ES" culture medium (Provosoli, 1968) to li b e r a t e any Dunaliella i n the gut. An additional 10- 15 ml. of the ES medium was added to each of these test tubes, which were then exposed to l i g h t . They were observed for the growth of the Dunaliella c e l l s . Similar experiments were carried out for the f i r s t three stages of C. plumchrus. In addition to the study of the actual feeding, a study was.made of the development of the gut, and therefore the capability of the animal to feed. Live n a u p l i i were fixed i n Henning's f i x a t i v e (a mixture of n i t r i c , and chromic acids, saturated mercuric chloride i n 60% alcohol, p i c r i c acid and absolute alcohol) for 12 to 24 hours and then washed i n iodine-alcohol. After being passed through a series of alcohols they were imbedded i n c e l l o i d i n and paraffin wax, and s e r i a l sections were made. One set of sections was stained in Mallory's t r i p l e s t a i n , the other i n Chlorazol Black E, and mounted i n Canada Balsam. After mounting, the sections were examined to determine the state of the alimentary t r a c t . Studies on Predation: In the predation experiments, the predators were exposed to different types and concentrations of zooplanktonic animals. Ten 20-ml. P e t r i dishes and ten 150-ml. jars were used. The P e t r i dishes were i n i t i a l l y f i l l e d with 10 ml. of pre-cooled, f i l t e r e d sea water, the food organisms counted and pipetted into the dishes with a minimum of water, and one predator was i n t r o -duced into each of the dishes. When the large containers were used, they were f i l l e d with 100 ml. of sea water, the prey organisms counted and introduced and one predator added to each of the containers. The experimental containers were incubated i n the cold room i n the dark to avoid aggregation of the prey and the predators owing to phototropism. After incubation for s i x to twelve hours, the condition of the gut of the predator was examined. The left-over prey animals were removed d i r e c t l y i n the case of the P e t r i dishes, whereas the contents of the large containers were emptied into a 2300-ml. finger bowl. The nature of the animals was examined, as well as any food i n the gut of the predator. The left-over prey was removed and the faecal p e l l e t s were picked out. The faecal p e l l e t s were l a t e r squashed on a s l i d e to examine the undigested parts using a compound microscope. The feeding rate (R) of the predator was calculated from the above information. Studies on food selection: Experiments to determine the selective nature i n the feeding of the developmental stages of E^ japonica and Cj^ plumchrus were carried out by using a mixture of phytoplankton, a mixture of phytoplankton and the pre-feeding stage of Artemia s a l i n a , and a mixture of zooplankton. The n a u p l i i of both the species were exposed to a mixture of Dunaliella and Coscinodiscus and a mixture of Dunaliella and Artemia. One nauplius was placed i n each of ten 20-ml. P e t r i dishes containing a known concentration of Dunaliella and Artemia. The dishes were then placed i n the dark in the cold room and incubated for a period of one hour. The selective feeding of these animals was detected by counting the number of Artemia, using a compound microscope, and the number of Dunaliella sp. c e l l s using a 17 Coulter Counter. The selective feeding on a mixture of Dunaliella and Coscinodiscus was carried out i n a simi l a r manner. In detecting the selective feeding exhibited by the copepodite stages of these two species of copepods, containers of 200- and 400-ml. capacity were used on the Rollordrum. The phytoplankton food types were mixed i n a larger container, shaken well and distributed equally among the experimental con-tainers. For counting purposes, the two species of food organisms were separated using a net of 15^u mesh si z e . Counts on each species of food were obtained i n the manner described i n the grazing experiment. When a mixture of phytoplankton and Artemia salina was used, Artemia eggs (San Francisco brine shrimp) were hatched i n the laboratory. Since i t was observed that the f i r s t day nauplius of Artemia does not feed, these could be used without affecting the phytoplankton counts. The phytoplankton was mixed and distributed equally into the containers. A 200-ml. aliquot was taken from each_ container for the estimation of the food concentration and then the Artemia n a u p l i i were added to both the controls and the experimental containers. These containers were then incubated on the Rollordrum i n the dark for 7 to 14 hours i n the cold room. After incubation a subsample of the prey organisms was taken for f i n a l counts. The n a u p l i i were removed from the subsamples before the counts were taken. The feeding rates for each of the.food organisms were calculated separately to allow comparison. When a mixture of zooplankton was used, prey animals of different sizes and species were introduced into j a r s (100 ml.) by pipettes and incubated for 6 to 12 hours i n the dark. After incubation, the contents of each j a r were emptied into a 300 ml. finger bowl to examine the condition of the predator, as well as to remove the left-over prey animals of each size category. The prey animals were removed by pipettes using a dissecting microscope. The feeding rates were estimated separately for each species of prey animal. For 18 the purpose of comparison, the number of prey animals eaten was multiplied by the dry weight of the prey animal to obtain the t o t a l weight of the animals. Studies on the seasonal v a r i a t i o n i n feeding of the C/2 and C/6 - female of  E. japonica and the C/5 C. plumchrus: Predation experiments were carried out under laboratory conditions i n the f a l l and summer for the C/2 and the C/6 - female of E^ japonica and i n spring, summer, and f a l l for the C/5 C. plumchrus to determine the seasonal var i a t i o n i n feeding. F i e l d Studies: , The seasonal and daily v a r i a t i o n i n the feeding of the animals i n the f i e l d was studied by examining the content of the alimentary tract i n various seasons and at different times of the day. The animals were collected with a one-meter or a seventy centimeter diameter net hauled v e r t i c a l l y from 225m. to the surface. Collections were made at two and three hour intervals through a 24-hour period. The alimentary tract of each specimen was examined with a dissecting microscope after placing the entire animal i n a small amount of water in a P e t r i dish. The percentage of animals with food was calculated for a l l the developmental stages of both species. The time of sunset and sunrise (pro-vided by the weather o f f i c e , Vancouver International Airport) was used as the c r i t e r i o n to decide between 'day' and 'night' times. Animals containing food were dissected by cutting off the t i p of the head and p u l l i n g off the urosome with the attached gut. The contents of the gut were squeezed onto a clean s l i d e , mounted i n water, and observed under a compound microscope for qual i t a t i v e analysis. I f warranted, a permanent mount of the squeezed contents was made i n Turtox CMC-S with an equal amount of Turtox CMC-10 mounting medium for l a t e r examination under higher magnification. Determination of the d i e l v e r t i c a l d i s t r i b u t i o n of the developmental stages  of E. japonica and C. plumchrus: 19 The d i e l v e r t i c a l d i s t r i b u t i o n of both the species i n the water of Howe Sound, Station 2, was studied for four months (December, 1968, to March, 1969) using Clarke-Bumpus nets (Clarke and Bumpus, 1950) at depths of 25, 50, 75, 100, 150 and 225 metres. These net hauls were taken at six-hour intervals for a period of twenty-four hours. A flow meter i n each plankton sampler enabled estimations to be made of the volume of water f i l t e r e d during a l l plankton tows. A quantitative estimation of the number of each develop-mental stage of both the species was then possible for each depth. Comparison of these estimates, over a 24-hour period was expected to indicate the d i e l v e r t i c a l d i s t r i b u t i o n . Trophic relationships of the developmental stages of E. japonica and C. plumchrus: In order to determine the trophic relationships of the developmental stages of the two species of copepods, the qu a l i t a t i v e and quantitative food requirements for each stage of development established from the laboratory experiments were to be related to the food available i n the f i e l d . Therefore, the available particulate organic food i n the natural environment was estimated by taking water samples from the bottom (225 and 230 m.) at Howe Sound, Station 2, over a ten-month period, and from near-surface water (50 m. and 100 m.) over a three-month period with a 1 6 - l i t e r Van Dorn bottle or a 9 6 - l i t e r sampler. From the collected water, two-liter samples were preserved with Lugol's solution. In the laboratory, three subsamples of 200 ml. were-taken from the preserved sample and f i l t e r e d through a 25 micron mesh net. The p a r t i c l e s larger than 25 microns were resuspended i n an equal amount of sea water and the samples run through the Coulter Counter to obtain a continuous size spectrum of particulate matter (see Sheldon and Parsons, 1967). This spectrum i s expressed as t o t a l particulate volume i n cubic microns per ml. versus the p a r t i c l e diameter i n microns. The qua l i t a t i v e analysis of the plankton was 20 made by microscopic examination of the samples. The l a b o r a t o r y r e s u l t s were then compared with the f i e l d r e s u l t s . CHAPTER I I I RESULTS Morphology of the feeding appendages of Euchaeta japonica and Calanus plumchrus: The complete results of the morphological study of the developmental stages of Euchaeta japonica and Calanus plumchrus are given i n Appendix A. A summary of the morphology of the feeding appendages i s given i n th i s section. The feeding appendages of the f i r s t four naupliar stages of E^ japonica consist of two pairs of antennae and a pair of mandibles. The f i f t h nauplius, i n addition to the above three pairs of appendages, has the rudiment of the f i r s t maxillae, and the six t h has two pairs of maxillae and a pair of maxillipeds. The mandibles of the f i r s t f i v e naupliar stages of E^ _ j aponica do not have teeth although a few small teeth are present i n the N/6 stage (Fig. 4F,. Appendix A). The maxillae of the N/6 stage (Figs. 4G and 4H) are simple, with a few lobes; the maxillipeds are simple and non-prehensile (Fig. 41, Appendix 8). The appendages of the copepodite stages of E^ japonica are well developed; the setae of the second antennae (Fig. 7), and the mandibles (Fig. A) are plumose, but those of the maxillae (Figs. 9 and 10) and maxillipeds (Fig. 11) are spinous. The maxillipeds are prehensile i n nature. The teeth on the inner surface of the coxa of the mandible are sharp and strong. The feeding appendages of the f i r s t four naupliar stages of C^ plumchrus (Figs. 13 to 15, Appendix A) are simi l a r to those of the corresponding stages in E. japonica. The fourth nauplius, i n addition to the f i r s t three pairs of appendages, has the rudiments of the f i r s t maxillae; the f i f t h nauplius has a pair of maxillae which are simple and lobular (Fig. 16A), while the s i x t h stage has both second maxillae and maxillipeds (Figs. 16C, and 16D, Appendix A). The appendages of the naupliar stages of C^ plumchrus are provided with a few plumosities while those of E. japonica are without plumosities. The mandibles of the N/4 to N/6 stages are provided with a few small teeth (Figs. 15D to 15F). 22 The appendages of the copepodite stages of Cj_ plumchrus are w e l l -developed with f i n e , closely arranged plumosities on the setae. The mandibles of a l l except the adult are provided with numerous short teeth (Figs. 20A - 20G). Laboratory feeding experiments of the naupliar stages of Euchaeta japonica: The naupliar stages two to s i x were tested for t h e i r a b i l i t y to feed on Dunaliella t e r t i o l e c t a (Table 1, Appendix B). The f i r s t nauplius i s normally passed within the egg (Lewis and Ramnarine, 1969); moreover, those that hatched did not feed. The second nauplius of E^ japonica did not feed on either l i v e or h e a t - k i l l e d c e l l s of t e r t i o l e c t a when exposed to concentrations ranging from 2,000 to 451,000 c e l l s per ml. (Table .1, Appendix B). This was also demonstrated with the culture technique. A d d i t i o n a l l y , examina-tion of both gross dissections and 10 micron s e r i a l sections did not show evidence of either an o r a l or an anal opening i n the N/1 stage. In contrast, feeding i n the N/3 stage was shown by both the feeding experiments (Table 1, Appendix B) and the culture technique. The t h i r d nauplius fed on h e a t - k i l l e d D. t e r t i o l e c t a at an average of 35,850 c e l l s per day. Ingestion increased from the N/3 stage through the N/6 to 73,660 c e l l s per day i n a concentration of 69,967 c e l l s per ml. except for a decrease at the N/5 stage (31,960 c e l l s per day) . The number of l i v e D^ t e r t i o l e c t a ingested by these developmental stages of E. . j aponica was less than that of dead D. t e r t i o l e c t a (range: 1 ,290 to 5,020 c e l l s per day). This was obtained by feeding experiments using the N/3 and the N/4 stages of E. japonica. The results i n Table 1, Appendix B show that the N/5 and the N/6 stages of E. japonica fed on the large diatom Ditylum b r i g h t w e l l i i (Fig. 3, Appendix C). The average volume of D. b r i g h t w e l l i i ingested by the N/5 and N/6 stages was more than the corresponding res u l t obtained with D. t e r t i o l e c t a . Table.1, Appendix B also reveals that the N/6 stage consumed 9,410 c e l l s per day of D^ b r i g h t w e l l i i . 23 Laboratory feeding experiments of the naupliar stages of Calanus plumchrus: The naupliar stages of C^ plumchrus were also fed food si m i l a r to that given to the naupliar stages of E^ japonica. The results of the feeding experiments are shown i n Table 2, Appendix B. The f i r s t nauplius did not i n -gest either Isochrysis galbana or h e a t - k i l l e d Dunaliella t e r t i o l e c t a . The second nauplius, i n contrast, fed h e a t - k i l l e d D. t e r t i o l e c t a (19,940 c e l l s per day). The th i r d nauplius ingested about three times as many c e l l s of TK_ t e r t i o - l e c t a as the second stage. Again the fourth stage ingested about three times as many c e l l s as the t h i r d stage did. • The ingestion decreased, i n the f i f t h nauplius, to approximately one half of that found for the fourth, while that of the sixth nauplius remained at a comparative low value of 69,470 c e l l s per day. The v a l i d i t y of the results obtained with the f i r s t and the second naupliar stages of C^ plumchrus was checked by the culture technique and examina-ti o n of sectioned material. The results of the culture technique indicate that feeding did not occur either i n the f i r s t or the second nauplius. The s e r i a l section examination indicated that the i n t e s t i n a l tract i s incomplete i n both the stages, the oral and the anal openings being absent i n the f i r s t nauplius, the oral opening being present but the anal opening absent i n the second nauplius. Using l i v e c e l l s of IK_ t e r t i o l e c t a for experiments involving the N/3 to N/6 stages of C^ plumchrus, i t was found that the number of l i v e c e l l s ingested per day was appreciably lower than the number of he a t - k i l l e d c e l l s . The t h i r d nauplius ingested 1,608 l i v e c e l l s and the six t h ingested 2,066 c e l l s per day. The naupliar stages were further tested for their a b i l i t y to feed on large, chain-forming diatoms. The fourth nauplius ingested an average of 53 c e l l s per day of Chaetoceros serpentrionalis (Fig. 4, Appendix C). Laboratory grazing experiments with the copepodite stages of E. japonica The results of the grazing experiments with the copepodite stages of 24 E_^_ japonica are presented i n Table 3, Appendix B. These results show that a l l of the copepodite stages fed on phytoplankton. Specimens of the C/l stage of E^ japonica were exposed to unicultures of the f l a g e l l a t e Dunaliella t e r t i o l e c t a , a small diatom, Phaeodactylum  tricornutum and large diatoms Ditylum b r i g h t w e l l i i and Coscinodiscus concinnus. These food species are i l l u s t r a t e d i n Appendix C. The feeding results show that the animals of the C/l stage readily ingested a l l of the above-mentioned food species except C^ concinnus. These animals consumed D^ b r i g h t w e l l i i more than JK_ t e r t i o l e c t a and Vj_ tricornutum. Specimens of the C/2 stage of E. japonica were exposed to both D.  b r i g h t w e l l i i and C. concinnus i n unialgal cultures. They consumed about 35.01 x 10'7 cubic microns of D. b r i g h t w e l l i i per day. The consumption of C.  concinnus was approximately half of the quantity of D. b r i g h t w e l l i i consumed. The C/3 stage ingested an average of 27.98 x IO'7 cubic microns of D. b r i g h t w e l l i i per day. The C/4 stage ingested 54.20 x 10^ cubic microns of D. b r i g h t w e l l i i per day. The consumption of 'DJ_ t e r t i o l e c t a by the C/4 stage was a l i t t l e less than an order of magnitude than the consumption of D.  b r i g h t w e l l i i (Table 3). Specimens of the C/5 stage, when exposed to unialgal cultures of D^ b r i g h t w e l l i i ingested 10.13 x 10? cubic microns per day while C/6 -female specimens ingested a l i t t l e less than t h i s . The C/6 - male of this species was also exposed to D^ t e r t i o l e c t a and 'DJ_ b r i g h t w e l l i i and they ingested 24.77 x 10^ cubic microns of D. b r i g h t w e l l i i and 23.13 x 10^ cubic microns of IK_ t e r t i o l e c t a per day. Laboratory grazing experiments of the copepodite stages of C. plumchrus: The results of the grazing experiments with the copepodite stages of C. plumchrus are presented i n Table 4, Appendix B. The copepodite stages fed on a variety of phytoplankton. Laboratory reared specimens of the C/l stage fed the IK_ t e r t i o l e c t a , the spiny, chain-forming diatom Chaetoceros 25 Figure I I I . Percentage of available Dunaliella t e r t i o l e c t a and Ditylum b r i g h t w e l l i i eaten by the copepodite stages of plumchrus. 16.0 C O P E P O D I T E S T A G E S O F C . P L U M C H R U S 26 serpentrionalis and a large, smooth chain-forming diatom Thalassiosira rotula. F i e l d collected specimens of the C/l stage were exposed to unia l g a l cultures of D. t e r t i o l e c t a (Table 4, Appendix B) and were found to consume slightly-more than the laboratory-reared specimens. The data i n Table 4, show that the C/2 stage fed t e r t i o l e c t a a l i t t l e more than the C/l stage captured from the f i e l d . The specimens of the C/3 stage fed a l l the three food species offered but the quantity of each food consumed was di f f e r e n t . The feeding results show that these animals consumed about 17.96 x 10'' cubic microns of D. b r i g h t w e l l i i . This quantity i s more than the volume of other two food species consumed (Table 4, Appendix B). Also, the C/4 stage fed more b r i g h t w e l l i i than t e r t i o l e c t a and Thalassiosira rotula. Specimens of the C/5 stage of C^ plumchrus were exposed to unialgal cultures of seven different phytoplankton of various sizes and shapes (Table 4, Appendix B). The feeding results show that these animals consumed a l l the seven types of food. The most preferred food type was Cj_ concinnus and the least preferred a one was D. t e r t i o l e c t a . The adult C/6 - female of C. plumchrus was exposed to unialgal cultures of t e r t i o l e c t a , D. b r i g h t w e l l i i , C. concinnus and C^ . serpentrionalis. The animals of the above stage did not ingest either of the l a s t two food species (Table 4, Appendix B). The volume of D. b r i g h t w e l l i i ingested was four-and-a-half times that of rK_ t e r t i o l e c t a . The results of a comparative study of the copepodite stages of C., plumchrus on t e r t i o l e c t a and D. b r i g h t w e l l i i are i l l u s t r a t e d i n Figure I I I . These results show that the food consumption of both the food species increases from the C/l to the C/4 stage and then declines. The figure shows also that the consumption by the C/6 - female i s less than that by the C/l stage on D.  t e r t i o l e c t a . Laboratory predation experiments of the developmental stages of E. japonica: The results of the predation experiments of the developmental stages of E. japonica are presented i n Table 5 to Table 9, Appendix B. The results i n Table 5 show that the s i x t h nauplius of japonica did not feed on the f i r s t day Artemia n a u p l i i . The copepodite stages one and two of this predator did, however, ingest a small quantity of Artemia n a u p l i i . The t h i r d copepodite stage ingested approximately three times the amount of Artemia ingested by the second stage. However, the number of Artemia n a u p l i i ingested d a i l y decreased from the C/3 to the C/4 stage. The C/5 stage consumed a s t i l l large quantity, approximately 22.17 n a u p l i i per day. Again, the con-sumption by the C/6 - female japonica decreased to one-third the consumption by the C/5 stage. The da i l y consumption i s further decreased to approximately 1.35 Artemia n a u p l i i i n the adult C/6 - male. A somewhat different trend was noticed when the fourth, f i f t h , and the sixth female stages of E.j aponica were fed on the second day Artemia n a u p l i i . These results are presented i n Table 6 of Appendix B. The results show that the C/4 stage ingested about 20 n a u p l i i per day, and the C/5 stage ingested approximately one-fourth of t h i s . The adult C/6 - female, however, consumed a l i t t l e more than the C/5 stage. The feeding results of the copepodite stages of japonica on the f i f t h day Artemia n a u p l i i are given i n Table 7, Appendix B. These results show an increase i n the consumption from the C/l stage through the C/4 stage. There i s a decrease i n the consumption from the C/4 to the C/5 stage. The animals of the C/5 stage consumed about one-third the quantity of Artemia n a u p l i i consumed by the C/4 stage (Table 6). The adult C/6 - female consumed approximately twice as many as the C/5 stage. In the case of the adult C/6 -male, the predation on the f i f t h day Artemia n a u p l i i was n i l . The results of a comparative study using C/4, C/5, and C/6 (male and female) of E^ j aponica as predators and Tigriopus cali f o r n i c u s (a harpacticoid copepod .- Fig. 12, Appendix C) are given i n Table 8, Appendix B. It i s seen from these - results that the da i l y consumption by the animals of the C/6 - female i s higher than the consumption by the other stages. The adult 28 Figure IV. Mean feeding rates of the C/l stage of japonica i n different concentrations of f i r s t day and f i f t h day Artemia n a u p l i i . V e r t i c a l l i n e s represent the 95% confidence l i m i t s (N = 10). 29 Figure V. Mean feeding rates of the C/4 and the C/5 stages of japonica i n different concentrations of Tigriopus c a l i f o r n i c u s . V e r t i c a l l i n e s represent the 95% confidence l i m i t s (N = 5). o I 1 1 1 ( 1 1 1 1 r 1 1*" H i 1 O O c o ^ - C V J o O O C O ' ^ - C M O O O C D ^ r C M O C V J C \ I C V | C V J C X J T - T - T - T~ Aop jad'dOD jad us^Da sndoubi i jo * O N 30 Figure VI. Mean feeding rates of the C/5 - female and C/5 - male of j aponica i n different con-centrations of f i r s t day Artemia n a u p l i i . V e r t i c a l l i n e s represent the 95% confidence l i m i t s (N = 10). Figure VII.:. Mean feeding rates of the C/6 - female and C/6 - male of j aponica i n different con-centrations of f i r s t day Artemia n a u p l i i . V e r t i c a l l i n e s represent the 95% confidence l i m i t s (N = 10). No.of first day Artemia nauplii per 1 0 0 mf. male did not feed on Tj_ c a l i f o r n i c u s . Some additional feeding results obtained for the copepodite stages of j aponica using a variety of gooplanktonic prey are given i n Table 9, Appendix B. The shape and the size of the prey are given i n Appendix C. I t i s seen from the above results that the C/l stage did not feed on barnacle n a u p l i i , Oncaea b o r e a l i s , and Scolecethricella. The C/3, C/5 and the C/6 -female stages of japonica were exposed to S c o l e c e t h r i c e l l a , and i t was found that feeding occurred only for the C/5 and the C/6 stages. The results show also that the C/6 - female ingested Scolecethricella a l i t t l e more than the C/5 stage did. Ostracod sp. was eaten i n b i t s and pieces by the C/5 and the C/6 - female stages. The C/6 - female ingested the urosome and the appendages of Gaidius Columbia Park, a calanoid copepod, while the C/6 - male showed no feeding. A graphical plot of the feeding rates of the C/l stage of japonica on cultures of the f i r s t and the f i f t h day Artemia n a u p l i i i s shown i n F i g . IV. The feeding rates of the predator are here displayed as a function of concen-t r a t i o n of the prey. -. , This figure shows that the maximum feeding rates on the f i r s t and the f i f t h day Artemia n a u p l i i are reached at different concentrations. The figure shows also that the feeding rates decline after the maximum value. The same trend i n the feeding rates i s observed when another prey organism, namely, T\_ c a l i f o r n i c u s , was used. This i s i l l u s t r a t e d i n Fig. V for the case of C/4 and C/5 stages of E. japonica. The results of a comparative study using the C/5 - male and female, C/6 - male and female copepodite stages of Ej_ j aponica are i l l u s t r a t e d i n Figs. VI and VII, respectively. Fig. VI shows that the mean feeding rates of the C/5 - female are only s l i g h t l y different from those of the male. Fig. VII shows that the feeding rates of the C/6 - female are consistently higher than those of the male. These results w i l l be discussed further i n Chapter IV. 32 Figure VIII. Mean feeding rates of the C/5 stage of E. japonica and the C/5 stage of C. plumchrus i n different con-centrations of f i r s t day Artemia n a u p l i i . V e r t i c a l l i n e s represent the 95% confidence l i m i t s (N = 10). 2 8 ^ Q. JO CIS E.japonica ^ ^ C/5 C.plumchrus .4 i J . s I / J . -I 1 1 1 : T — ! — 30 35 4 0 45 No.of first day Artemia nauplii per 100ml. —\— 50 —i— 55 6 0 Fia • v.m. 33 Laboratory predation experiments of the developmental stages of C. plumchrus: The results of the predation experiments i n which the developmental stages of plumchrus were used as predators are given i n Table ll 1, Appendix B. The results i n Table 11, show that the N/6 and the C/l and C/2 stages of C^ plumchrus did not feed on the f i r s t day Artemia n a u p l i i . The specimens of the C/3 stage, however, fed a small quantity. The number of Artemia n a u p l i i d a i l y ingested by the C/3 stage was found to be 0.5. The number ingested i n -creased from the C/3 through the C/5 stage of the predator (Table 10, Appendix B). But, i n going from the C/5 to the C/6 - female developmental stage, the quantitative consumption decreased. Laboratory predation experiments of the C/5 stage copepodite of E. japonica  and C. plumchrus: The results of a comparative study using C/5 stage copepodites of both E. j aponica and C^ plumchrus as predators and the f i r s t day Artemia n a u p l i i as prey are i l l u s t r a t e d i n Fig. VIII. This figure shows that the feeding rates of the C/5 stage of E. japonica are consistently higher than those of the C/5 stage of C^ plumchrus. These results w i l l be discussed further i n Chapter IV. Experiments on the food s e l e c t i v i t y of the developmental stages of E. japonica: The results of selective feeding of the developmental stages of E.  j aponica are shown i n Tables 12 to 20, Appendix B. The data i n Table 12 show that the N/6 stage of JE^ japonica did not feed on either the diatom C.  concinnus or the f i r s t day Artemia n a u p l i i but fed t e r t i o l e c t a when exposed to mixtures of (C^ concinnus + te r t i o l e c t a ) and (Artemia n a u p l i i + D.  t e r t i o l e c t a ) . The data i n s e r i a l numbers 1 to 3, Table 13 show that the C/l stage of E^ j aponica consumed a greater quantity of zooplankton than phyto-plankton. This evidence was obtained from experiments using (D. tertiolecta' + f i r s t day Artemia nauplii) or (D. b r i g h t w e l l i i + the f i r s t day Artemia nauplii) 34 as prey organisms. However, when a prey mixture consisting of (D^ b r i g h t w e l l i i + D.  t e r t i o l e c t a + Artemia nauplii) was used, the C/l stage of japonica did not show consistency i n i t s preference for the zooplankton. This i s seen from the s e r i a l numbers 4 to 6 of Table 13, Appendix B. In one instance ( s e r i a l number 4), the Artemia nauplius was most preferred and Ih_ t e r t i o l e c t a was least preferred. In th i s case the predator (C/l E. japonica) ingested 8.0 micrograms of Artemia nauplius per day. The amount of D. b r i g h t w e l l i i ingested from the mixture was almost the same as the Artemia ingested, but the amount of t e r t i o l e c t a ingested was one-fourteenth of that of Artemia n a u p l i i ingested. Using the same three food types, another series of experi-ments ( s e r i a l numbers 5 and 6 of Table 13) revealed that the C/l stage selected D. b r i g h t w e l l i i and D. t e r t i o l e c t a i n that order of preference. The data i n s e r i a l number 7, Table 13, show that the C/l stage preferred the f i r s t day Artemia n a u p l i i to the n a u p l i i of C\_ plumchrus. This predator ingested 1.047 micrograms of Artemia n a u p l i i per day ( s e r i a l number 7, Table 13), which i s two orders of magnitude more than the consumption of the n a u p l i i of C. plumchrus. - The preference for the f i r s t day Artemia n a u p l i i to the phytoplankton was shown also by the C/2 to C/6 - female stages of E^ japonica, as seen i n Tables 14 to 17. The data i n s e r i a l number 4, Table 18, show that the adult female of E. japonica preferred the n a u p l i i of E^ _ japonica to the n a u p l i i of C.  plumchrus and the barnacle n a u p l i i , The consumption of the n a u p l i i of E.  japonica was 42.15 micrograms per day, which i s about four times the amount.of n a u p l i i of C^ plumchrus consumed. The barnacle n a u p l i i were not eaten by the predator. Using a mixture of Artemia eggs and the f i r s t day Artemia n a u p l i i , i t was found that the- C/6 - female stage of E. japonica ingested only the 35 Figure IX. Mean feeding rates of the copepodite stages of E. japonica i n different concentrations of a mixed culture of f i r s t day and f i f t h day Artemia n a u p l i i . The results are f o r : (A) The C/l stage, (B) The C/2 stage, (C) The C/3 stage, (D) The C/4 stage, (E) The C/5 stage, and (F) The C/6 -female. V e r t i c a l l i n e s represent the 95% confidence l i m i t s (N = 10). A o p j s d *dOD j a d ua;D9 ji|dnDU * ; J V J O ' O N 36 n a u p l i i and not the eggs ( s e r i a l number 5, Table 18, Appendix B). This was also true with C/4 stage ( s e r i a l number 4, Table 16). The data i n Table 19 show that the adult males of japonica preferred phytoplankton. This evidence was obtained from experiments using either a mixture of (D. b r i g h t w e l l i i + the f i r s t day Artemia nauplii) or (T. rotula j- the f i r s t day Artemia n a u p l i i ) . The results of the selective feeding experiments of the copepodite stages of japonica on a mixture of the f i r s t day and the f i f t h day Artemia n a u p l i i are i l l u s t r a t e d i n Figs. IXA to IXF. The data are also separately tabulated (Table 20, Appendix B) i n terms of the dry weights of food consumed. This Table, as well as the above mentioned figures, w i l l now be examined. Fig. IXA show that the C/l stage of E. japonica ate more f i r s t day Artemia n a u p l i i than the f i f t h day Artemia n a u p l i i . The average d a i l y con-sumption of the f i r s t day Artemia n a u p l i i i s 14.57 micrograms (Table,20), which i s about four times the amount of the f i f t h day Artemia n a u p l i i consumed. The feeding results of the C/2 stage of E^ japonica on the mixture of foods mentioned above are i l l u s t r a t e d i n Fig. IXB. Again, these animals fed more f i r s t day Artemia n a u p l i i and less f i f t h day n a u p l i i . The mean d a i l y con-sumption of the f i r s t day Artemia n a u p l i i was 26.05 micrograms, which i s approximately twice the amount of the f i f t h day Artemia n a u p l i i eaten. From Fig. IXC to IXF i t i s found that the animals of the C/3 to C/6 -female of E_^_ j aponica also ate more f i r s t day Artemia n a u p l i i and less f i f t h day Artemia n a u p l i i . The d a i l y consumption of the f i r s t day Artemia n a u p l i i by weight i s about three times that of the f i f t h day Artemia n a u p l i i for a l l the above developmental stages of Ej_ japonica. The results of selective feeding of the copepodite stages of E_;_ japonica were s t a t i s t i c a l l y analysed using analysis of variance methods. The results of the analysis are shown i n Table 21, Appendix B. They reveal that the feeding 37 rates are s i g n i f i c a n t l y different (1) i n various concentration of prey, (2) between different developmental stages of the predator, and that (3) there i s a s i g n i f i c a n t interaction between the concentration of food and the developmental stages. The analysis also shows that there i s no s i g n i f i c a n t difference i n the selection of the two sizes of prey used. The data i n Table 18, Appendix B, indicate that the animals of the C/6 - female E. japonica prefer the l i v e food organisms to the dead ones. This evidence was obtained i n experiments using l i v e and dead second day Artemia n a u p l i i i n a mixture. The average number of l i v e Artemia n a u p l i i ingested per day was 4.32 which i s twice as many as the dead ones eaten. Experiments on the food s e l e c t i v i t y of the developmental stages of C. plumchrus; The results of the selective feeding experiments of the developmental stages of C. plumchrus are presented i n Tables 22 to 28, Appendix B. The data i n Table 22 show that the N/6 stage of C^ plumchrus ate neither the diatom C. concinnus nor the zooplankton f i r s t day Artemia nauplius, but that i t did feed on the f l a g e l l a t e t e r t i o l e c t a . The feeding experiments done using the copepodite stages of C. plumchrus w i l l now be examined. The data i n Table 23 (Appendix B) show that the C/l stage of C^ plumchrus avoided eating the f i r s t day Artemia n a u p l i i from a mixture of foods and ate only the phytoplankton. From a mixture of (D.  t e r t i o l e c t a + b r i g h t w e l l i i ) the animal consumed 1.2 micrograms of D.  t e r t i o l e c t a per day,, which i s twice as much as the consumption of b r i g h t w e l l i i ( s e r i a l number 1, Table 22, Appendix B). The data i n Table 24 suggest that the C/2 stage of C. plumchrus pre-ferred D..brightwellii to D. t e r t i o l e c t a . This stage consumed an average of 0.90 microgram of D. b r i g h t w e l l i i per day, which' i s more than the consumption 38 of t e r t i o l e c t a . The mixture of food offered to the C/3 stage consisted of D.  t e r t i o l e c t a and the f i r s t day Artemia n a u p l i i . From this mixture the animal of the C/3 stage consumed an average of 22.7 micrograms of Artemia n a u p l i i and 1.3 micrograms of D. t e r t i o l e c t a per day, indicating i t s preference for the former food species. The values just shown are the averages of s e r i a l numbers 3 and 4, Table 25, Appendix B. When the mixture consisted of D. t e r t i o l e c t a and TK^  b r i g h t w e l l i i , an average of 0.60 microgram (mean of s e r i a l numbers 1 and 2 of Table 25) of t e r t i o l e c t a per day was consumed. This i s almost twice as much as the consumption of D. b r i g h t w e l l i i . A reversal i n selective feeding i s once again shown by the animals of the C/4 stage which prefer phytoplankton to zooplankton. This i s borne out by the data i n Table 26, Appendix B. The results here are si m i l a r to those of the C/l stage. I t was found that when a mixture of C_^_ concinnus and f i r s t day Artemia n a u p l i i was used as food, the C/4 stage ate only the former. But when a mixture of (D. t e r t i o l e c t a + b r i g h t w e l l i i ) was offered, the animal selected the l a t t e r food species. An average of 2.15 micrograms of D. brigh t - w e l l i i per day was consumed (mean of s e r i a l numbers 3 and 4 i n Table 26), which i s almost twice as much as that of D. t e r t i o l e c t a consumed. The data i n Table 27, Appendix B, suggest that the animals of the C/5 stage prefer zooplankton to phytoplankton, thus p a r a l l e l i n g the selective . feeding behaviour of the e a r l i e r C/3 stage. Thus, from a mixture of (D.  t e r t i o l e c t a + f i r s t day Artemia n a u p l i i ) , an average of 19.0 micrograms of Artemia n a u p l i i and:1.2 micrograms of D. t e r t i o l e c t a (average of s e r i a l numbers 3 and 4 of Table 27).was consumed per day by the C/5 stage. When the food mixture consisted of (D. b r i g h t w e l l i i + D. t e r t i o l e c t a ) , the animal preferred D. b r i g h t w e l l i i , s i m i l a r to the behaviour of the C/4 and C/6 stages. The figures for the average consumption by the C/4 are: 3.28 micrograms of 39 b r i g h t w e l l i i and 2.6 micrograms of D. t e r t i o l e c t a (from s e r i a l numbers 1 and 2 of Table 27). The results i n Table 28 indicate that the adult females prefer phyto-plankton to zooplankton l i k e the animals of the C/l and C/4 stages, as mentioned e a r l i e r . The results of the selective grazing of the copepodite stages of C. plumchrus on different sized p a r t i c l e s of TK_ t e r t i o l e c t a are given i n Table 29, Appendix B. The animals were exposed to p a r t i c l e s ranging i n size from 50.20 to 1604.04 cubic microns. The data i n the Table show that the C / l stage grazed on different sized p a r t i c l e s i n the two concentrations ( s e r i a l numbers 1 and 2). The animals of the C/2 stage also were exposed to the same food species, containing p a r t i c l e s of the size range 50.22 to 1607.04 cubic microns i n the f i r s t concentration ( s e r i a l number 1, Table 29) and range 50.22 to 803.52 cubic microns i n the second concentration ( s e r i a l number 2, same Table). In both the concentrations, the maximum food consumed was from the p a r t i c l e s of size 50.22 cubic microns. Likewise, animals of the C/3 and C/4 stages ingested the maximum of D. t e r t i o l e c t a of size 50.22 cubic microns i n both the concen-t r a t i o n s , but the C/5 stage, however, preferred the largest size of D. t e r t i o -l e c t a available. The C / l , C/3, C/5, and C/6 - female of C. plumchrus were exposed to a mixture of different-sized chains of C^ serpentrionalis. Table 30 shows that the C. serpentrionalis available for grazing was i n the volume range 43.20 to 2,764.80 cubic microns. The C/l animals preferred p a r t i c l e s of the size 86.40 cubic microns from the f i r s t concentration and of the size 1,382.40 cubic microns from the second concentration. The animals of the C/3 stage did not ingest several sizes of the chains of C. serpentrionalis offered. They preferred chains of the size 172.80 cubic 40 Figure X. Mean feeding rates of the C/2 stage of E^ japonica i n different concentrations of f i r s t day Artemia n a u p l i i i n the summer and i n the f a l l . V e r t i c a l l i n e s represent the 95% confidence l i m i t s (N = 10). Figure XI. Mean feeding rates of the C/6 - female stage of E. japonica i n different concentrations of f i r s t day Artemia n a u p l i i i n the summer and i n the f a l l . V e r t i c a l l i n e s represent the 95% confidence l i m i t s (N = 10). <L> E - E o LL i/) Q * CO V 6 - 9 - 00 OJ p CVJ -2 LP I D z 1 \ \ S 1 b f 1 E o o a. C L D 0 c 0 +-> £_ < > o T3 to £_ o c r • -i 1 1 1 1 i 1 i i c o c o ^ C M O O o O ^ ^ ^ 0 0 0 ^ ADp Jad poaadco jad Tia^pa Ti|dnDu;0'ON 41 microns from the f i r s t concentration ( s e r i a l number 1, Table 30) and of the size 345.60 cubic microns from the second concentration ( s e r i a l number 2, Table 30). The animals of the C/5 stage grazed readily on the entire s i z e -spectrum of p a r t i c l e s available to them from the f i r s t concentration ( s e r i a l number 1, Table 30, Appendix B). From the results obtained with the second concentration, however, i t i s seen that the size 43.20 cubic microns has been excepted and the rest of the p a r t i c l e s grazed ( s e r i a l number 2 of Table above). In both the concentrations, the maximum was ingested from the size 1382.40; cubic microns. In the case of the C/6 - female, Table 30 shows that grazing occurred only for a few categories of p a r t i c l e s i z e , and preferred p a r t i c l e s of different sizes from two concentrations. Using a mixture of EL_ b r i g h t w e l l i i p a r t i c l e s of sizes ranging from 4,546.21 to 145,478.72 cubic microns, i t was found that ingestion by C/3 to c/6 — female animals of C. plumchrus occurred from almost a l l the sizes of p a r t i c l e s . However, the preference shown f o r a s p e c i f i c size of D. b r i g h t w e l l i i was not the same for a l l the developmental stages. For instance, the C/3 and the C/5 stages preferred p a r t i c l e s of volume 36,369.68 cubic microns, the C/4 preferred p a r t i c l e s of volume 72,739.36 cubic microns and the adult females preferred the smallest p a r t i c l e s of volume 4,546.21 cubic microns. The results of the above paragraph are found i n Table 31, Appendix B. Experiments on the seasonal v a r i a t i o n i n the feeding of the C/2 and the C/6 -female of E. japonica: The feeding rates of the specimens of the C/2 stage on the f i r s t day Artemia n a u p l i i i n the f a l l and summer are i l l u s t r a t e d i n Fig. X. I t i s seen from the figure that the animals ingested more i n the f a l l than i n the summer. The feeding rates i n the f a l l at concentrations 10 and 30 Artemia n a u p l i i per 42 100 ml. are s i g n i f i c a n t l y higher than i n the summer. The feeding results of the animals of the C/6 - female of E. japonica i n the f a l l and summer are shown i n Fig. XI. The figure reveals that the feeding rates i n the summer are higher than i n the f a l l , and that they are s i g n i f i c a n t l y different at concentrations 10.0 and 40.0 Artemia n a u p l i i per 100 m. Experiments on the seasonal v a r i a t i o n i n the feeding of the C/5 stage of  C. plumchrus: The feeding results for the C/5 stage of C. plumchrus i n the spring, summer and f a l l are given i n Tables 4, 33 and 34, Appendix B. The data i n the above Tables indicate that thes§ animals eat more readily i n the spring than i n the summer or f a l l . Using the f l a g e l l a t e D. t e r t i o l e c t a , i t was found that the animals ingested an average of 14,240.0 c e l l s per day. The above quantity i s an order of magnitude less than that ingested i n the spring (Table 4). Food consumption, again, decreased i n the f a l l and i t was found to be one-ninth of the average number of c e l l s ingested i n the spring. The f l a g e l l a t e lj_ galbana and the diatom costatum were completely avoided by the animals i n the summer (Table 33, Appendix B). This phenomenon, namely, the avoidance of food i n the summer, was i l l u s t r a t e d also when food was offered i n mixed form (Table 35, Appendix B). The mixtures t r i e d consisted of (D. t e r t i o l e c t a + concinnus) or ( f i r s t day Artemia n a u p l i i + D..  b r i g h t w e l l i i ) . The specimens of the C/5 stage consumed only the diatom C. concinnus. Results of F i e l d Observations  Temporal v a r i a t i o n i n the feeding of the copepodite stages of E. japonica: . :The results of the observation of the alimentary tracts of the copepodites of E. japonica during the day and night of various seasons are given i n Table 36, 43 Appendix B. The data show that the f i r s t copepodite stage d i d not have food i n the guts at any time the o b s e r v a t i o n was made, i e . , whether observed on a d a i l y or a seasonal b a s i s . The C/2 and the C/3 stages contained food o n l y i n the f a l l and w i n t e r seasons. For the C/2 stage, i t i s i n d i c a t e d t h a t the feeding occurred during the day i n the f a l l season, and during the n i g h t i n the w i n t e r season. Observations of the gut of the C/3 stage i n d i c a t e that feeding occurred during the n i g h t , i n both the f a l l and w i n t e r . The number of specimens of the C / l to C/3 stages of E.japonica a v a i l a b l e f o r the examination of the ali m e n t a r y t r a c t was not s u f f i c i e n t to draw any c o n c l u s i o n on the observations made. Observations on the gut of the C/4 stage of the above species are given i n Table 36, Appendix B. These observations show t h a t a maximum number of animals had food i n the a l i m e n t a r y t r a c t i n the s p r i n g , and a minimum number i n f a l l . ; The number of animals of t h i s developmental stage w i t h food i n the w i n t e r was twice as many as i n the summer, which i s a l s o a l i t t l e l e s s than i n the s p r i n g . With regard to the d a i l y v a r i a t i o n i n the feeding, of the C/4 stage, the data i n the above mentioned Table show t h a t , i n the spring, and summer, a l a r g e number of animals contained food i n t h e i r guts from c o l l e c t i o n s madevduring the day. In the w i n t e r , examination of: the alimentary t r a c t r e v e a l e d t h a t animals w i t h food i n the guts were h a l f as many i n the day as they were i n the n i g h t . The gut o b s e r v a t i o n of the animals, of the? C/5 stage i n the s p r i n g shows t h a t 9.31% of the animals examined contained food i n the a l i m e n t a r y t r a c t (Table 36, Appendix B). The number of animals, c o n t a i n i n g food i n the summer i s approximately one-fourth of the number i n the s p r i n g . I n the f a l l , the number of animals w i t h food i s f u r t h e r decreased, and i s approximately h a l f as many as i n the summer. Again, i n w i n t e r , the number of animals w i t h food i n the gut was 6.75%. This i s an i n c r e a s e over the value found f o r the summer. 44 The r e s u l t s of feeding observations made i n the f i e l d f o r the C/5 stage of ja p o n i c a during both n i g h t and day show th a t there i s no c l e a r i n d i c a t i o n of d a i l y v a r i a t i o n i n the s p r i n g . During the summer and f a l l , a l a r g e percentage of the animals observed had food i n t h e i r guts during the day. During the n i g h t , a very small number of animals contained food i n the summer, but none of the animals contained food i n the n i g h t during the f a l l season. The r e s u l t s f o r the w i n t e r i n d i c a t e that there i s more feeding during the n i g h t than during the day. The seasonal v a r i a t i o n i n the feeding observed f o r the C/6 - female of E.. j a p o n i c a i s shown i n Table 36, Appendix B. There was an increase i n the feeding during the f a l l and w i n t e r i n r e l a t i o n to the s p r i n g and summer. Observations oh the d a i l y v a r i a t i o n i n d i c a t e that the animals of the C/5 stage d i d not show much d i f f e r e n c e i n feeding i n the s p r i n g and summer. The values i n the same Table show t h a t , during the f a l l season, 8.0% of the animals con-ta i n e d food at n i g h t , which i s approximately twice the number i n the day. In the w i n t e r , the number of animals w i t h food during the day was three times as many as during the n i g h t . More fe e d i n g , t h e r e f o r e , occurs during the day than during the n i g h t . Seasonal and d a i l y observations made on the C/6 - males of j a p o n i c a show that none of the, specimens contained food at any time (Table 36, Appendix B). Temporal v a r i a t i o n i n the feeding of the copepodite stages of C. plumchrus: The r e s u l t s , of the observation on the alimentary t r a c t s of the copepodite stages of C^ plumchrus during days and n i g h t s of v a r i o u s seasons are given i n Table 36, Appendix B. I t i s to be noted here that the develop-mental stages of t h i s species do not occur throughout the year, except the C/5 stage. Therefore, a complete set of r e s u l t s f o r a l l the fo u r seasons could be obtained only f o r the C/5 stage. As shown in: the Table,, 32.0% of the animals of the C/l and the C/2 45 stages had food i n t h e i r alimentary tracts at the time of capture i n the spring season. The results of the observations for day and night also indicate that the above two developmental stages feed more during the day than during the night (see Table 36). The number of animals of the C/3 stage which contained food i n the spring wag a l i t t l e more than the number of animals with food of the C/2 stage. Here, again, a larger number of these animals had fed during the day than during the night. The results of analyses of the gut content for the C/4 stage i n the spring show that 77.0% of the animals observed contained food, which i s approximately twice as many as the C/3 stage. There i s not much difference i n the feeding during the day and night. The results obtained for the C/5 stage show that 40% of the animals had food i n the guts i n the spring season. The results also show that none of the animals contained food i n the summer and winter, but 1.88% of the animals did have food i n the f a l l . The above results indicate that the C/5 stage feeds well i n the spring, and feeds poorly or rarely during the other three seasons. The observations recorded for the day and night collections indicate that the C/5 specimens feed more during the night than during the day. In the spring, 57.5% of the C/5 specimens caught during the night had food i n the gut; this, was almost three times the percentage of animals with food during the day. In the f a l l , 2.25% of the animals caught during the night contained food while only 1.5% contained food during the day. The C/6 - female stage of C_^  plumchrus only occurred during the winter season. No food was observed i n the guts for observations made at any time during this season. Qualitative gut analysis: The gut contents of the animals of both E..japonica and C. plumchrus Figure XII. Die l v e r t i c a l d i s t r i b u t i o n of the develop-mental stages of E. japonica i n December, 1968. D E C E M B E R 1 9 6 8 47 Figure X I I I . D i e l v e r t i c a l d i s t r i b u t i o n of the developmental stages of E. japonica i n January, 1969. J A N U A R Y 1 9 6 9 2 5 5 0 7 5 LU LU 2 1 2 5 Q_ LJ Q 1 5 0 1 7 5 -2 0 0 2 2 5 C/1 C / 2 C / 3 C / 4 C / 5 C / 6 f e m a l e D E V E L O P M E N T A L S T A G E S O F £ . J A P O N I C A . B n i g h t O d a y s c a l e • • M a n i m a l C / 6 m a l e 48 Figure XIV. D i e l v e r t i c a l d i s t r i b u t i o n of the developmental stages of japonica i n February, 1969. 49 Figure XV. D i e l v e r t i c a l d i s t r i b u t i o n of the developmental stages of E. japonica i n March, 1969. MARCH 1969 S night Ea day scale N/1-6 C/1 C/2 C/3 C/4 C/5 C/6 female C/6 male DEVELOPMENTAL STAGES OF E.JAPQNICA. 50 were also analysed q u a l i t a t i v e l y , and the results follow. The contents of the copepodite stages of E^ japonica showed crustacean remains such as b i t s and pieces of appendages (Fig. 15, Appendix C) and the mandibles. The gut contents from C. plumchrus, however, appeared only as a green mass. The re-cognisable part of this green mass consisted of the diatoms Coscinodiscus sp. (Fig. 16, Appendix C), S. costatum, and Thalassiosira sp. Di e l v e r t i c a l d i s t r i b u t i o n of the developmental stages of E. japonica: The d i e l v e r t i c a l d i s t r i b u t i o n of the developmental stages of E.  japonica during the months of December, 1968 to March, 1969 i s plotted i n Figs. XII to XV. In these figures, the depths from which the animals were collected are plotted against the number of animals collected per cubic meter. The d i s t r i b u t i o n of the eggs of E^ japonica i s not shown i n the figures since very few eggs were collected. However, eggs were collected close to the bottom, at about 225 m., both during the day and the night. The number of n a u p l i i collected per cubic meter of water was also very low. These animals were found to be distributed near the bottom from January to March, 1969 both day and night (Fig. XIII to XV). In the month of December, 1968 (Fig. X I I ) , they were collected at about 100 m. during the day; during the night they were found between 100 and 225 m. The animals of the C/l stage of E. japonica also occurred close to the bottom i n the months of February and March, 1969 (Fig. XIV and XV), both during the day and night. In December, 1968 and January, 1969 (Fig. XII and X I I I ) , they were never found below 100 m. In December, 1968, they were collected between 50 and 100 m. during the night; during the day they were collected at 75 m. C/l stages were not available during the night i n January, 1969. A few animals of the C/2 stage were collected during the months of January to March, 1969 (Fig. XIII to XV). The c o l l e c t i o n for the month of 51 December, 1968, was a l i t t l e more substantial. This c o l l e c t i o n i s represented in Fig. X I I , and i t i s inferred from t h i s figure that the C/2 stage of E.  japonica was distributed from 50 m. to the bottom during the day. This d i s t r i -bution i s seen to be denser i n the 50 - 100 m. region of depth. In the night, these (C/2) animals moved closer to the surface. In January (Fig. X I I I ) , they were found near the surface during the day and between 25 and 75 m. during the night. In the month of February (Fig. XIV), these animals were found froim 75 m. down to the bottom during the day, and at night they were found near the surface. In March (Fig. XV), they occurred from 150 m. to the bottom during the day, while at night they were found above 50 m. The C/4 stage occurs between 75 and 150 m. during the day i n December, 1968 (Fig. X I I ) . During nights of t h i s month, they were found i n greatest numbers between 25 and 75 m., and i n smaller numbers from 75 down to 150 m. In January (Fig. X I I I ) , they were distributed between 25 and 225 m. during the day, and at night between 25 and 150 m. In February (Fig. XIV), the C/4 stage could be caught during the day between 75 and 225 m. During the night, they were found from the surface down to the bottom. In March (Fig. XV), these animals were collected during the day between 75 and 225 m. During the night, they migrated closer to the surface. The animals of the C/5 stage were found to occur below 100 m. during the day i n December, 1968 and March, 1969, but i n January and February they occurred throughout the water column. In March, the animals were found close to the surface at night, whereas i n the other months, the night d i s t r i b u t i o n was from the surface to the bottom. The above d i s t r i b u t i o n data are depicted i n Fig. XII to Fig. XV. The C/6 - females of E. japonica occurred more or less from 100 m. to the bottom during the day i n a l l the four months. At nights i n the months of December and March, they were distributed throughout the water column, whereas 52 at nights i n January and February, they were never found below 100 m. These data appear i n Fig. XII to Fig. XV. A few C/6 males of the above species were collected i n the net tows. However, they were never found above 75 m. at any time during the above periods of observation. D i e l v e r t i c a l d i s t r i b u t i o n of the developmental stages of C. plumchrus: The d i e l v e r t i c a l d i s t r i b u t i o n of the developmental stages of C.  plumchrus i n the months of December, 1968, to March, 1969, are plotted i n Fig. XVI and XVII. The developmental stages do not occur throughout the year. The eggs, the n a u p l i i , the C/l and the C/2 stages were found to occur only in March. The C/3 and the C/4 stages occurred mainly i n A p r i l * , but started appearing i n l a t e March. The C/5 stage occurred from May* to December, and the C/6 stage (adult) occurred mainly i n January and February. The adult females were more abundant than the males, and therefore only the females were considered f o r the study of the d i s t r i b u t i o n of the adults. I t i s seen from the Fig. XVII that the eggs of C. plumchrus occur at the bottom (225 m.) both day and night, but the n a u p l i i occur throughout the water column. A greater number of the n a u p l i i was found near the bottom at night. The animals of the C/l and the C/2 stages have also been found to occur throughout the water column both day and night (Fig. XVII), but aggregated near the surface (to a lesser extent) and near the bottom (to a greater extent) during the night. The C/3 stage, which was found i n l a t e March, appeared during the day as two very small patches, one of which was near the surface and the other near the bottom. At night, the deep patch ascended to the surface. * Although the specimens were not actually collected i n these months for the d i s t r i b u t i o n a l studies, their occurrence during t h i s period of the year had already been recognised i n the e a r l i e r stages of this work. 52a Figure XVI. D i e l v e r t i c a l d i s t r i b u t i o n of two copepodite stages of C. plumchrus: The C/5 stage (December, 1968), the C/5 - and C/6 - female (January, 1969), and the C/6 - female (February, 1969) . DECEMBER 1968 JANUARY 1969 FEBRUARY 1969 C/5 C/6-female C/6- female COPEPODITE STAGES OF C . PLUMCHRUS. D i e l v e r t i c a l d i s t r i b u t i o n of the developmental stages of C. plumchrus i n March, 1969. M A R C H 1 9 6 9 D E V E L O P M E N T A L STAGES O F . C . P L U M C H R U S . 54 Figure XVIII. Concentrations of organic p a r t i c l e s i n the water samples taken from 230 m. depth i n the winter (December, 1968). DIAMETER OF INDIVIDUAL SM.PART lCLES(mic rons ) 3 .57 4 . 4 9 5 .66 7;12 8 ^ 9 8 11.3 1 4 . 3 18.0 1.0 .A o--o Sm.particles, x — x Lar.particles. - T4 .0 LO > r~ r~ -12 .0 X O .JJ1 5 i - 1 0 0 P —1 O o 1 m c: - 8 . 0 o n O :RO z o • - 6 . 0 NS. OA AA.0 C: m 14.3 18.0 22 J6 2 8 5 3 5 . 9 4 5 . 3 57.0 71.9 DIAMETER OF INDIVIDUAL PARTlCLES(microns) 55 The late stage of the C/5 of Cj_ plumchrus occurred i n the month of December. These animals were found to be distributed i n deeper water both day and night (Fig. XVI). In January, the population of the C/5 stage i s sparse, as most of them have matured into the C/6 adult stage. The adults occurred throughout the water column both day and night i n January (Fig. XVI). In February, they were found from 100 m. to 225 m. during the day, while during the night they were found at depths of 100 to 150 m. Estimation of particulate matter i n the near surface and near deep water i n  Howe Sound during different seasons of the year: The organic particulate matter i n the surface water i s derived mainly from (1) primary and secondary production, (2) faecal p e l l e t s , (3) decayed algae and zooplankton, and (4) p a r t i c l e s derived from t e r r e s t r i a l o r i g i n washed into the sea by runoffs. The quantitative estimations of particulate matter present i n the surface and bottom water i n different seasons of the year are shown i n Table 37, Appendix B. The largest amount of particulate matter was found i n the winter. The t o t a l volume of p a r t i c l e s at 50 m. i n February, 1969, was 13.32 x 10 cubic microns per ml. The volume of p a r t i c l e s of the bottom water from December to February was two orders of magnitude greater than the volume of p a r t i c l e s of the near surface water. The q u a l i t a t i v e analysis of the water from the surface revealed that i t contained the diatom Coscinodiscus sp. and calanoid copepods Oncaea borealis. The water from the near bottom contained the cope-pods Oncaea borealis and Scolecethricella sp. and Ostracod i n December; i n January and February, i t contained d e t r i t u s . The zooplankton i n the month of December make up the major bulk of the volume of particulate matter. The rest of the particulate matter i n the near bottom water (in December) was composed mainly of detritus of the size 3.57 to 45.3 microns i n diameter (Fig. XVIII). The volume of particulate matter available i n the spring i n the near 56 Figure XIX. Concentrations of organic p a r t i c l e s i n the water samples taken from near-surface (100 m.) and near-bottom (230 m.) of Howe Sound i n March, 1969. 57 surface water was 26.75 x 10~* cubic microns per ml ( p a r t i c l e s of the s i z e range 3.57 to 18.0 microns i n diameter). The p a r t i c l e s c o n s i s t e d of S.  costatum, Chaetoceros sp., D. b r i g h t w e l l i i , T h a l a s s i o s i r a sp., and f l a g e l l a t e s . The volume of p a r t i c u l a t e matter i n the near bottom i n the s p r i n g was 26.94 x 10"* cubic microns (Table 36, Appendix B) . The p a r t i c l e s present i n the bottom water were mainly the diatom Coscinodiscus sp. and d e t r i t u s . The d i s t r i b u t i o n of p a r t i c l e s i n the near surface and near bottom water i n the s p r i n g season i s i l l u s t r a t e d i n F i g . XIX. The peaking i n the f i g u r e f o r the surface water i s between 5.66 and 8.98 microns, whereas f o r the bottom water the peaking occurs at 14.3 microns. 4 In the summer, the bottom water contained a volume of 49.79 x 10 cubic microns, which i s l e s s than that a v a i l a b l e i n the s p r i n g . There was no water sample taken from the surface during the summer. In the f a l l , the q u a n t i t y and the v a r i e t y of food a v a i l a b l e i n the water decreases both i n the surface and the bottom water w i t h respect to s p r i n g . In the surface water, 18.99 x 10^ cubic microns of p a r t i c u l a t e matter was-4 a v a i l a b l e ; i n the bottom water, the corresponding f i g u r e was 87.22 x 10 cubic microns. Thus i n the f a l l , p a r t i c u l a t e matter i n the bottom water was a l i t t l e more compared to the summer. 58 CHAPTER IV DISCUSSION OF RESULTS The results of the present study as well as. those of previous workers ( F u l l e r , 1937; R i g l e r , 1961; M u l l i n , 1963) suggest that the feeding of planktonic crustaceans i s controlled by many factors. These factors, varying throughout the l i f e of the organism can be of a morphological nature, with respect to both the nature of the l i f e history stages and type of available food. They can also be physicochemical, with respect to interaction between the internal and external environment, or they can be associated with the con-centration of available food. In assessing the feeding of the l i f e history stages of both Euchaeta  j aponica and Calanus plumchrus, i t i s suggested that the early stages are controlled by the development of the alimentary tract and by the amount of : yolk material stored i n the egg. The results of the culture experiments indicate that feeding does not occur i n the f i r s t two naupliar stages of either species. Observations of prepared sections of the N/1 indicate that neither a mouth nor an anus i s present, thus supporting the suggestion that the N/1 does not feed. The or a l opening however, i s present i n the N/2 stage of both the species, while the anal opening i s s t i l l absent. This condition i s believed to prohibit feeding (Marshall, 1965, 1966), although Jacobs (1961) found that the second nauplius of Pseudodiaptomus coronatus Williams could feed twenty minutes after b i r t h . In the feeding experiments however, the N/2 of E^ japonica does not feed, though the N/2 of C. plumchrus does. I t i s possible that the N/2 of E. j aponica takes food but too l i t t l e to be detected by the techniques employed. Although the second nauplius of C. plumchrus was found to feed, the amount ingested was s u f f i c i e n t l y small that the N/1 and N/2 stages of both the species are c l a s s i f i e d as "pre-feeding" stages for purposes of discussion. 59 In the absence of feeding i t i s presumed that energy for growth, etc., would depend on the yolk i n the body, and possibly dissolve matter i n the sea. I t has been found by Lewis and Ramnarine (1969) that the survival of the eggs and the naupliar stages of japonica reared i n the laboratory was increased by the addition of zinc, cobalt, and a chelating agent, Na2EDTA, to the sea water from the natural environment. I t has been presumed that the increase i n the survival was due to the addition of one or more of the substances to the medium. The results of the culture experiments i n the present work indicate that the N/3 stage of both species i s a feeding stage. This stage i s equipped with a complete alimentary t r a c t and with less yolk than i n the f i r s t two naupliar stages. The small quantity of yolk and the presence of a complete alimentary tract i n the N/3 stage of the species may make i t necessary, and possible, for them to depend on an external source of food. The capability of the animal to feed i s related to the morphology of the mouth parts. This has also been noticed by other workers (Wickstead, 1962; Amori and Anraku, 1963: B r o d s k i i , 1967). I t was observed i n the present study that the f i r s t three pairs of the naupliar appendages i n E_^  j aponica are simple with no plumosities, and that they never formed a ' f i l t e r i n g basket' (Cannon, 1928) which i s essential for f i l t e r i n g the food p a r t i c l e s . The teeth on the inner surface of the mandibles of N/6 of E. japonica (Fig. 4F, Appendix A) are not sclerotized as i n the copepodites (Fig. 8, Appendix A). Sclerotized strong, sharp teeth are necessary to feed on p a r t i c l e s with hard or tough texture. Because of the presence of simple mouth parts and the absence of sclerotized teeth i n the N/6 stages the animals of this stage may be incapable of ingesting f i r s t day Artemia n a u p l i i (Table 5, Appendix B). The structural details of the mouth parts of the f i r s t two n a u p l i i of C. plumchrus reveal that they are simple, without any spines or hooks. The 60 mouth parts of the l a t e r naupliar stages are provided with plumosities which are neither regularly nor closely arranged (Figs. 13, 14 and 15 of Appendix A). The naupliar appendages of this species do not form a f i l t e r i n g basket with the mouth parts as i s observed i n the copepodites. The teeth on the l a t e r naupliar stages (Figs. 15 E and F of Appendix A) are not sclerotized and are small. In presumed accordance with the structural development of the mouth parts, the n a u p l i i of C. plumchrus are herbivores (Table 11 of Appendix B). I t has been seen i n the present work that the l a t e r naupliar stages (N/6 of E. japonica and the N/4 of C. plumchrus) are capable of feeding on large p a r t i c l e s (eg. C. sep., D. bright.) as well as on small p a r t i c l e s (eg. rK_ t e r t i o l e c t a ) . Since the N/4 of plumchrus was found to feed on C. serpentrionalis, i t can be assumed that the N/5 and the N/6 stages of the same species are also capable of feeding on th i s food type. With the simple appendages and di s t a n t l y placed plumosities, and without a f i l t e r i n g basket in the l a t e r naupliar stages of both the copepod species, the consumption of large diatoms by them i s surprising. This has also been observed by Marshall (1965) for the young stages of finmarchicus, which throws doubt on the general assumptions that the e a r l i e r the stage the smaller w i l l be the food organism i t can accept. In a study of the setulation i n C. finmarchicus, Marshall found that the distance between setules i n those n a u p l i i i s not . smaller than i n the adult. Therefore, the n a u p l i i have the same c a p a b i l i t i e s as the adult to f i l t e r and retain large p a r t i c l e s . The n a u p l i i of both the species feed more readily on the he a t - k i l l e d D. t e r t i o l e c t a than on the l i v e t e r t i o l e c t a . The preference for the heat-k i l l e d species i s probably because they can f i l t e r these c e l l s more eas i l y than the l i v e c e l l s . This behaviour suggests that, i n the f i e l d , the n a u p l i i may feed on detritus and diatoms, and that they might not readily obtain small f l a g e l l a t e s . In the sea, d e t r i t a l carbon nearly always far exceeds the l i v i n g 61 material i n quantity (Strickland, 1965). Parsons and Strickland (1962) determined the chemical composition of the detritus and suggested that i t could well act as food. This might explain the importance to planktonic animals of d e t r i t a l material and the non-moving diatoms. The copepodite stages of Ej_ japonica were found to prefer Artemia n a u p l i i to the diatom IK_ b r i g h t w e l l i i . This selection can be associated with the predatory nature of the mouth parts to indicate that the nature of the food i s , i n part, determined by the type of feeding appendages. The C/6 - male however has degenerate mouth parts and i s primarily a herbivore although, i n the absence of plant food, i t w i l l feed on Artemia n a u p l i i . In the herbivorous species, C^_ plumchrus, the second antennae., ., the maxillae, and the maxillipeds of the copepodites C/l to C/5 have plumose setae and the mandibles have numerous f i n e , short teeth. (Appendix A). The C/6 - female has degenerated mouth parts with complete loss of teeth on the mandibles. The copepodite stages C / l , C/2, C/4 and C/6 - female are primarily herbivorous, showing preference for phytoplankton. The C/3 and C/5 stages, however, prefer Artemia n a u p l i i to phytoplankton. This selective behaviour of the C/3 and C/5 stages i s quite unexpected. A s i m i l a r behaviour has been reported i n the l i t e r a t u r e for C^ finmarchicus. The female of t h i s species grazed Artemia n a u p l i i at higher rates than diatoms (Mullin, 1963) but this preference was reversed i n the copepodite stages C/4 and C/5 (Anraku and Omori, 1963). The feeding results of the copepodites of E. j aponica and C. plumchrus also indicate a size preference. The C/l and C/2 stages of C. plumchrus did not ingest f i r s t day Artemia n a u p l i i (average length 375 ^u) whereas the l a t e r stages did. S i m i l a r l y , S colecethricella sp., a calanoid copepod approximately 1.4 mm. long, was not ingested by the C/l and the C/3 stages of E. japonica but was by the C/5 and the C/6 - female stages. Also, the C/l stage of E^ 62 japonica did not ingest the diatom C. concinnus (diameter approximately 78^u), while the C/2 stage did. In feeding experiments with Gaidius Columbia Park, of length approximately 2.1 mm., the prey was not eaten by the C/6 - female of E. japonica. The predator held the copepod with the maxillae and maxillipeds and t r i e d to f i t i t into the mouth by turning the prey over and oyer again u n t i l the narrow end of the prey was i n the mouth. Once the narrow end was i n the mouth, the predator t r i e d to push the large body of the prey into i t s mouth but did not succeed. Although no lower l i m i t was found with either E^ japonica or Cj_ , plumchrus. I t appears, then, that there.is a size relationship between the feeding animal and the prey. Elton (1927) states that the size relationship i s an important reason for the existence of the food chain, because what i s too large and too small to be consumed by one organism can be eaten by another. In this way, small items, after passing through one or two intermediary steps, become i n d i r e c t l y available to large predators. There are awkward or unmanageable shapes of prey organisms which may be cumbersome to the predator or the grazer. This has been indicated in the f a i l u r e of the C/6 - female of E. japonica to feed on barnacle n a u p l i i from a mixture of barnacle n a u p l i i , n a u p l i i of E. japonica, and n a u p l i i of C. plumchrus. The f a i l u r e of the copepods to eat barnacle n a u p l i i could possibly be due to the presence of the f r o n t a l horns on the l a t t e r . S i m i l a r l y , Parsons and LeBrasseur (1968) observed that certain shapes of food may be unsuitable for feeding by C^ p a c i f i c u s . These authors report that, while C. pacificus obtains 16 to 18% of i t s body weight from Thalassiosira (a large chain-forming diatom), i t obtains only 2% of i t s weight from Chaetoceros (a long, spiny chain-forming diatom). They suggested (page 333) that the shape of Chaetoceros was probably the c r i t i c a l factor i n determining the lack of 63 s u i t a b i l i t y o f the food. The movement of the prey could a l s o be one of the f a c t o r s a f f e c t i n g f e e d i n g . I f the prey organism moves f a s t e r than the reeding animal, i t i s l i k e l y to escape. This i s b e l i e v e d to be the reason f o r the absence of feeding of the C / l of E. j a p o n i c a on the a d u l t s of the c y c l o p o i d copepods Oncaea b o r e a l i s which move much f a s t e r than the predator. This could a l s o be one of the reasons why the C/6 - male of E^ j a p o n i c a does not eat T i g r i o p u s c a l i f o r n i c u s (a h a r p a c t i c o i d copepod) .Another reason could be that the male E_. j a p o n i c has g r e a t l y reduced mandibular blades. " Even w i t h i n s u i t a b l e s i z e ranges however, marine p l a n k t o n i c copepods p r e f e r some food to a g r e a t e r extent than o t h e r s . The p r e f e r r e d s i z e of food i s detected by measuring the fee d i n g r a t e of copepods on a s i n g l e type of food when no other food i s a v a i l a b l e . A comparison between these t e s t s , w i t h d i f f e r e n t types of food , i s d i f f i c u l t to determine because so many other f a c t o r s a f f e c t the r a t e of feeding ( M u l l i n , 1963). Measurements of feeding on v a r i o u s types o f food i n a mixture overcome t h i s d i f f i c u l t y s i n c e any f a c t o r other than s e l e c t i v e feeding i s assumed to a f f e c t consumption of a l l foods i n the mixture e q u a l l y . The r e s u l t s of such experiments however, can o n l y i n d i c a t e the food or foods present i n the experimental mixture that the copepod w i l l eat most r e a d i l y . I t does not n e c e s s a r i l y show what food the copepod eats i n nature s i n c e l a b o r a t o r y c o n d i t i o n s are not i d e n t i c a l to f i e l d c o n d i t i o n s . I t has been observed that the copepodites of C^ plumchrus show a preference f o r the l a r g e food p a r t i c l e s , both i n s i n g l e and mixed c u l t u r e s . I t might be mentioned here t h a t s t a r v a t i o n has not a f f e c t e d s e l e c t i v i t y i n the feeding of these animals. The p r e f e r e n t i a l removal of l a r g e c e l l s has a l s o been observed by Conover (1960) i n the fee d i n g of C^ finmarchicus and by M u l l i n (1963) i n the feeding of C. h e l g o l a n d i c u s , C. finmarchicus and C. hyper-boreus on both mixed and u n i a l g a l c u l t u r e s . P e t i p a (1959a) n o t i c e d that A c a r t i a c l a u s i i s e l e c t e d the l a r g e s t round c e l l s from a l g a l s p e c i e s . 64 The preferential removal of large c e l l s of a single species of food has been demonstrated with Cj_ helgolandicus, which removes the longer chains i n a suspension of Asterio n e l l a (Mullin, 1963). There i s no clear evidence to this effect i n the present work. The large p a r t i c l e s are more l i k e l y to be retained by a f i l t e r feeding organism because of the size of the p a r t i c l e retained depends on the space between the plumosities on the setae. Brooks and Dodson (1965) consider that animals choose food on the basis of s i z e , abundance, and e d i b i l i t y , and the ease with which i t i s caught. They further suggest that: (1) predators choose the largest food available, but the selec-tion of food i n herbivorous zooplankton depends on the f i l t e r i n g mechanism that removes the p a r t i c l e s , or (2) selection i s based on chemical or surface q u a l i t i e s of the food. The selective feeding behaviour of the copepodites of E. j aponica feeding on a mixture of two sizes of Artemia n a u p l i i shows that no preference i s exhibited for either the small or large n a u p l i i at the 0.05 conf. l e v e l . Food organisms with a smooth surface may be d i f f i c u l t to grip by a predatory animal and may be unsuitable as a food source. This has been indicated by the f a i l u r e of the C/4 and the C/6 - females of E. japonica to feed on Artemia eggs from a mixture of Artemia n a u p l i i and Artemia eggs. I t i s also possible, of course, that the eggs were so small that they could have slipped through the appendages of the predators. The non-motile nature of the eggs does not seem to be the reason for the f a i l u r e of the eggs to be ingested be-cause i t has been shown that the C/6 - female i s capable of feeding on the non-motile, dead, second day Artemia n a u p l i i . Even though the developmental stages of the two species of copepods have a preference for a s p e c i f i c size and type of food, they appear to be opportunists and feed on available food i n the absence of a preferred food. The feeding behaviour of the C/4 and the C/6 - female of C^ plumchrus and the C/6 - male of E. japonica are good examples i l l u s t r a t i n g t his behaviour. When 65 fed on a mixed culture, the animals selected phytoplankton and avoided zooplankton; but the same animals ate zooplankton when no other food was available. Digby (1954) describes this type of feeding as a special type of mixed feeding. , Three more factors which possibly influence the diet of the animal appeared during the course of the present investigation. They are: (1) the a v a i l a b i l i t y of the food, (2) the age, and (3) the physiological condition of the animal. In the spring, there i s plenty of food available i n the sea, and there i s every p o s s i b i l i t y for the animal to come across the right kind, s i z e , and concentration of food. In the winter, when food i s scarce, the animal eats l e s s . This may be due to the fact that there i s less chance of having the right s i z e , right food type and the right concentration of the food available. The reduced food consumption i n the winter may also have been induced by a reduced metabolic rate. Although this could also be a direct consequence of the age and sexual maturity of the animal. Conover (1960) worked on the feeding behaviour and respiration of marine planktonic Crustacea. He concluded that carnivorous animals are generally more active than herbivorous animals because they must go i n search of the prey and must then overcome the natural reluctance of the prey to be caught by using their physical strength and swiftness. On the other hand, herbivorous animals feed while they swim, with a more or less continuous expenditure of energy, t h e i r food having, at best, extremely feeble powers of escape. Conover also points out that the carnivorous animals need more energy to maintain themselves i n the water column against the negative buoyancy due to the presence of a considerable weight of inert organic material as exoskeleton and dense muscle protein. In the case of herbivorous animals the buoyancy i s maintained by the large amount of o i l present i n the body. The difference i n the food consumption of the n a u p l i i of the two 66 species, i s believed to be due to certain basic differences between them. One of these differences i s the amount of yolk present i n the body. The nauplius of j aponica contains a large quantity of yolk, while nauplius of C_. plumchrus, has very l i t t l e yolk and therefore may depend more on external sources of food. Another difference i s the nature of the developing appendages. Naupliar stages 4 to 6 of Cj_ plumchrus have better developed appendages than those of E. japonica and consequently are more active. Because of t h e i r active movements, they encounter food p a r t i c l e s more often i n nature than the n a u p l i i of E. japonica and, thus, might eat more food than the l a t t e r species. In addition to these difference the naupliar stages of plumchrus occur in the early spring when there i s plenty of food available i n the sea. The naupliar stages of E. japonica, on the other hand, occur a l l through the year. The copepodites of E^ japonica and Cj_ plumchrus again exhibit certain differences i n the i r d a i l y average food consumption which may also be explained on morphological grounds. For example, the C/5 of E. japonica consumed twice as much food as the C/5 of C. plumchrus when feeding on f i r s t day Artemia n a u p l i i . This may be associated with the morphologically adapted for a carnivorous diet by the C/5 of E_^  japonica. The corresponding stage of C. plumchrus, i s better adapted for a herbivorous habit and showed a poor cap a b i l i t y of handling the zooplankton. The effect of the morphology of the mouth parts on the quantitative consumption i s again evident i n the feeding behaviour of the male and female animals of the C/5 and C/6 stages of E. japonica. Where there i s no morpholo-g i c a l difference between the sexes (C/5 male and female) the quantity of Artemia n a u p l i i consumed was s i m i l a r . Where morphological differences.do exist (C/6 - male and female), the quantity of Artemia n a u p l i i consumed was not s i m i l a r . The C/6 - female, with well developed mouth parts, ate much more than the C/6 - male, with degenerate mouth parts (Table 5, Appendix B). 67 Similar low feeding by the male copepod has been observed by e a r l i e r workers. Mullin (1963) found that the grazing rate of the male of C_^_ helgolandicus fed on Ditylum was one-third to one-tenth of that of the female. Raymont and Gross (1941) found that the grazing rate of the male C_;_ finmarchicus was one-f i f t e e n t h to one-fortieth of that of the female. In the l a t t e r two cases i t i s not known whether or not the difference i n the quantitative consumption of food was due to any difference i n the morphology of the mouth parts. I t was also observed that the quantity of food ingested by the various developmental stages of E^ j aponica, was different even when the mouth parts were s i m i l a r . In general, i t i s assumed that the smaller the stage of development, the smaller the amount of food consumed. In other words, the s a t i a t i o n point increases as the size of the feeding animal increases. There i s also a relationship between the prey size and the consumption by the predator, the quantity decreasing as the prey size increases. This was observed i n the case of the C/4 and C/5 stages of E. japonica fed on the f i r s t day Artemia n a u p l i i . In the case of C^ plumchrus, the size to s a t i a t i o n point r e l a t i o n -ship seems to hold up to the C/4 stage, but beyond that the consumption decreased as the size of the feeding animal increased (Fig. I I I ) . The decreased con-sumption by the C/5 and the C/6 - female of C. plumchrus suggests that there are some factors, other than the size of the animal which are operating. The same trend i n feeding was also indicated by these animals i n the f i e l d observa-tions. The lower food requirement for the C/5 and C/6 stages may be due to a low metabolic rate. In the C/5 stage i t may be the change from sexually pre-mature stage to the mature stage that affects the feeding. The C/6 - female, which i s a short-lived animal, probably does not depend on an external source of food since i t s growth i s complete arid i t s main function, the process of egg-laying. The low consumption of food by the C/6 - female may also be due to degenerated mouth parts. Arashkevich (1968) makes the same observation i n 68 his study of the copepods of the Northwestern P a c i f i c . The amount of food consumed by the animals also varies with the nature of the food. In contrast the early C/4 stage of C^ plumchrus was said to consume more of the diatom C_^  serpentrionalis than the costatum. One would expect the C/5 stage to have consumed more S. costatum than C.  serpentrionalis, because the l a t t e r has small, thin spines. The unexpected results may have been due to taste or size of the food. For example, Parsons et a l . (1967) found that a mixture of Calanus pacificus and the euphausiid, Euphausica p a c i f i c a , when fed on long-spined Chaetoceros chains, consumed only 2% of th e i r body weight. The authors think that i n th i s example the long spines of the Chaetoceros appear to have been a c r i t i c a l factor i n determining the unsuitable nature of the food. Feeding i s also known to be influenced by the food concentration. I t has been found to be d i r e c t l y proportional to the food concentration up to a certain l i m i t , and beyond that i t i s inversely proportional (Mullin, 1963; Parsons et a l . , 1968). The predators i n the present study (copepodite stages of E^ japonica) also show the same relationship between the feeding rate and concentration of the prey (Fig. IX). It has been observed by Rigler (1961) that Daphnia (water flea) maintains a steady feeding after the ' c r i t i c a l concentration' because of the i n a b i l i t y of the animal to ingest or digest any more food. In the case of the predators, the degree of success i n hunting i s proportional to the degree of concentration of prey or, i n other words, the more abundant the food i s , the easier i t i s for the animal to procure food. The chances of encountering the prey become greater, i n a dense population of food. However, i n extreme concentrations of prey, the decrease i n consumption implies that the predator i s constantly encountering the food without doing active work. The driving force of hunger, therefore, may be lo s t and the animal does not feed. 6 9 The effect of the concentration of food on the feeding of the animal i s also shown i n the gut observation of animals from the f i e l d . A high percentage of the animals had food i n the gut when there was an abundance of food available i n the sea, eg. i n the spring season. Thus, the feeding of copepods seems to be closely t i e d up with the food cycle i n the sea. This relationship between the feeding of the animal and the food cycle i n the f i e l d , i s i l l u s t r a t e d by the C/5 stage of C\_ plumchrus. In the laboratory feeding experiments, the amount of food consumed i n the spring by the C/5 stage was more than i n the summer or i n the f a l l . The amount of food available i n the sea was also more i n the spring than at any other time of the year. I f the seasonal p e r i o d i c i t y of the animals i s controlled purely by an external factor, namely the a v a i l a b i l i t y of food, the C/5 would have eaten substantially i n the laboratory during a l l the seasons where the concentration of food species offered was always high. Since the C/5 stage executed seasonal p e r i o d i c i t y i n the feeding i n the laboratory, there may also be an internal factor which controls the feeding as w e l l as the external factor of food con-centration. E. japonica does not show a clear seasonal v a r i a t i o n pattern i n the f i e l d as C. plumchrus does. There are two main reasons which could account for this difference: (1) E. japonica has several broods i n a year, and (2) the copepodites of t h i s species are primarily predatory i n habit. Daily v a r i a t i o n i n feeding i s pronounced i n Cj_ plumchrus and less pronounced i n E^ japonica. I t has been shown i n the gut analysis of these animals that most of the C/l and the C/2 stages of C. plumchrus eat during the day and not during the night. In contrast, the C/5 stage of C. plumchrus feeds primarily at night. This d a i l y v a r i a t i o n i n feeding may be related to the d i e l v e r t i c a l d i s t r i b u t i o n of the animals. That i s to say, a large number of the C/l and C/2 stages of C. plumchrus, which feed during the day, are 70 found to occur near the surface are exposed to more food because the surface water i s r i c h i n phytoplankton. A s i m i l a r observation has been made by Wimpenny (1938) , who found that many copepods migrated to the surface during the night and to the bottom during the day and that the percentage of copepods with food i n the alimentary tract was higher i n the night than during the day. Only a s l i g h t d a i l y v a r i a t i o n i n feeding has been observed i n the copepodite stages of E^ _ japonica, that they feed more during the day than during the night. The d i s t r i b u t i o n a l patter of E. japonica may not be closely related to the v e r t i c a l d i s t r i b u t i o n of these animals i n the sea. Even though i t appears that optimum feeding occurs wherever and whenever the food supply i s abundant, i t i s never the case that the food i s actually completely used up. Parsons et a l . (1967) noticed, for example, that grazing occurred down to some low l e v e l and then ceased. This seems to be a natural ecological phenomenon which safeguards a population from t o t a l extinction. Slobodkin (1968) explains i t as follows: "... predation acts i n i t i a l l y to increase the mortality rate above the b i r t h rate. I f there was no compensatory increase of the b i r t h rate, the prey population would be completely eliminated. However, there i s for a l l species a certain r e s i l i e n c e i n the reproductive rate. This r e s i l i e n c e i s primarily due to the fact that i n any population the removal of some of the animals leaves u n u t i l i s e d the resources these individuals would have used, thus increasing available resources for the survivors. The number of young born tends to be higher than i n the absence of predation and the mean l i f e expectancy of the animals that are not taken by the predator may be higher than i t otherwise would have been." Trophic relationships: The term 'trophic relationship' can be simply defined as the quantity of food required by the animals versus the quantity of food available i n the f i e l d . The quantitative food requirements of the various developmental stages of both species have been found to be different. The N/3 stage of C. plumchrus requires the food ( l i v e t e r t i o l e c t a ) to be i n the concentrations of about 5 . . • ' 4 10.83 x 10 cubic microns per ml. to consume 44.91 x 10 cubic microns per day. 71 The N/3 stage of E_i_ j a p o n i c a r e q u i r e s the food to be i n con c e n t r a t i o n s of about 11.80 x 10^ cu b i c microns per ml. to consume 36,120 cubic microns per day. In both these cases,, the c o n c e n t r a t i o n of food a v a i l a b l e i n feeding experiments may not have been h i g h enough to produce maximum fe e d i n g . Parsons e t a l . (1967) have shown t h a t the C/3 and C/4 stages of C. plumchrus r e q u i r e the food con-'5 • 7 c e n t r a t i o n t o be 60.0 x 10 cubic microns per ml. to consume about 20.0 x 10 cub i c microns per day; t h i s i s not even the maximum r a t i o n of the animals. I t has a l s o been shown (Parsons et a l . , 1967) that the C/5 stage of C. plumchrus r e q u i r e s a c o n c e n t r a t i o n of 55.0 x 10"* c u b i c microns per ml. to o b t a i n i t s maximum r a t i o n from Skeletonema and m i c r o f l a g e l l a t e s i n the s p r i n g season. But i t has been found i n the present work th a t the c o n c e n t r a t i o n of food a v a i l -able ,in the sur f a c e waters o f Howe Sound i n the s p r i n g i s 26.75 x 10"* cubic microns per ml. which i s lower than the c o n c e n t r a t i o n needed f o r maximum feedi n g . The C/5 stage of Cj_ plumchrus i n the f a l l , consumed a volume of 16.28 x 10^ c u b i c microns per day of C^ _ concinnus i n a c o n c e n t r a t i o n of 45.07 x 10^ c u b i c microns per ml. The e s t i m a t i o n of p a r t i c u l a t e matter i n the. . t o t a l p a r t i c u l a t e matter sea water at t h i s time however, r e v e a l s that the co n c e n t r a t i o n of A in the s u r f a c e sea water i s 18.99 x 10^ cu b i c microns per ml., and i n the near 4 bottom water i t i s 87.22 x 10 cubic microns per ml. Here again, the n a t u r a l c o n c e n t r a t i o n seem to be lower than what i s necessary f o r optimum fee d i n g s . I t may be necessary to have even a higher c o n c e n t r a t i o n of food than t h a t a v a i l a b l e i n the l a b o r a t o r y because the competition f o r the same food species w i l l be i n g r e a t e r i n n a t u r e . This suggests that the animals may not get the r e q u i r e d r a t i o n per day from the sea, even under optimum c o n d i t i o n s . The C / l stage of E. j a p o n i c a consumed, i n the l a b o r a t o r y , a volume 6 of 91.56 x 10 c u b i c microns per day of D. b r i g h t w e l l i i from a c o n c e n t r a t i o n of 11.43 x 10^ cu b i c microns per ml. Since t h i s stage of development occurs near the bottom of the water column i n the sea, the food requirement of t h i s 72 animal as measured i n the l a b o r a t o r y i s compared w i t h the a v a i l a b l e food i n the bottom water. The volume of p a r t i c l e s a v a i l a b l e i n the bottom water 4 6 ranges from 49.84 x 10 to 12.94 x 10 c u b i c microns per ml., e x c l u d i n g the 4 8 zooplankton, and from 35.45 x 10 to 97.47 x 10 cubic microns per ml. i f the volume of zooplankton i s i n c l u d e d (Table 37, Appendix B). At the h i g h e r c o n c e n t r a t i o n there i s ample food, but w i t h the presence of the a v a i l a b l e types of u n s u i t a b l e food (eg. , S c o l e c e t h r i c e l l a ) , food i n nature i s i n lower con c e n t r a t i o n s than, that used i n the l a b o r a t o r y to o b t a i n the r e q u i r e d r a t i o n per day. •Ifn In the above examples i t i s suggested that the a v a i l a b l e p a r t i c u l a t e matte] nature i s l e s s than the c o n c e n t r a t i o n of food r e q u i r e d to produce maximum feeding i n the l a b o r a t o r y . I t should be remembered, however, th a t the l a b o r a t o r y e s t i m a t i o n s cannot be d i r e c t l y a p p l i e d to f i e l d c o n d i t i o n s . They only show what the animal would do w i t h the s i t u a t i o n o f f e r e d i n the l a b o r a t o r y . I t i m p l i e s t h a t animals eat more i n the l a b o r a t o r y where the food supply i s both r e g u l a r and high but l i m i t e d i n s c o r e . To s u r v i v e i n the f i e l d , they may r e q u i r e a - d i f f e r e n t q u a n t i t y than what i s i n d i c a t e d from the l a b o r a t o r y feeding experiments. 73 CHAPTER V SUMMARY AND CONCLUSIONS This study has revealed that the naupliar stages N/1 and N/2 of Euchaeta j aponica Marukawa and Calanus plumchrus Marukawa are incapable of feeding, since the N/1 stages have neither o r a l nor anal openings, while the N/2 stages have only the former. The n a u p l i i of both E. japonica and C. plumchrus begin to feed on small h e a t - k i l l e d and l i v e f l a g e l l a t e s such as Dunaliella t e r t i o l e c t a , at the N/3 stage. The N/6 stage of E. japonica can feed on single large diatoms such as Ditylum b r i g h t w e l l i i . From the N/4 stage onwards, C. plumchrus can feed on chain-forming diatoms such as Chaetoceros serpentrionalis. The food s e l e c t i v i t y experiments with the N/6 stage of the two species reveal that the naupliar stages are purely herbivorous. This herbivorous habit has been associated with the morphology of the mouth parts. The quantity of food consumed by the naupliar stages of E^ japonica i s a l i t t l e less than that of C\_ plumchrus. This may be due to the presence of a large quantity of reserve food i n the form of yolk in the body of the n a u p l i i of E^ japonica, while there i s only very l i t t l e yolk i n the body of C. plumchrus. The copepodites C/l to C/5 and C/6 - females of E^ japonica are pro-vided with strong teeth on the mandibles and spines on the maxillae and prehensile maxillipeds. The C/6 - males have degenerate mouthparts, with loss of teeth on the mandibles. In spite of the adaptation for a carnivorous habit, the C/l to C/5 stages and the C/6 - females are omnivorous although, i f provided a mixture of zooplankton and phytoplankton, they w i l l s e l e c t i v e l y feed on the former. The C/l to C/5 copepodite stages of C^ plumchrus are provided with numerous small teeth on the mandibles and fine plumose setae on the second 74 antennae, maxillae, and maxillipeds. Both the C/6 - males and females have degenerate mouthparts. In spite of the adaptation for a herbivorous habit, the C/3 to C/6 - females are omnivorous i n habit. The C/3 and the C/5 stages w i l l s e l e c t i v e l y feed on zooplankton whereas the other stages w i l l s e l e c t i v e l y feed on phytoplankton i f provided with a mixture of zooplankton and phytoplankton. The copepodite stages of C_;_ plumchrus p r e f e r e n t i a l l y remove large food p a r t i c l e s and show a d i s t i n c t seasonal and d a i l y v a r i a t i o n i n feeding. This v a r i a t i o n i n feeding i s associated with the i r v e r t i c a l d i s t r i b u t i o n i n the water column. The copepodite stages of E_^_ japonica show less pro-nounced seasonal and d a i l y v a r i a t i o n . Their feeding does not seem to be closely t i e d up with their v e r t i c a l d i s t r i b u t i o n . The lack of d i s t i n c t seasonal or d a i l y v a r i a t i o n i n feeding of the copepodite stages of Ej^ j aponica indicate that they are "opportunist" type feeders. The adults i n both the species consume less food than the e a r l i e r copepodite stages. The low consumption of food could be attributed to the degenerated mouthparts as well as to the physiological condition of these animals. Thus, the developmental stages of both species show qua l i t a t i v e and quantitative differences i n feeding. These differences aire associated with the morphology of the mouthparts, sex, s i z e , age, and physiological condition of the feeding animal as well as the s i z e , shape, m o t i l i t y , and the concentra-tion of the food organisms. The quantity of food consumed by the developmental stages of the two species i n the laboratory when compared with the quantity of food available i n the sea, suggests that these animals could not meet their d a i l y require-ments i n the sea. I t also suggests that they feed more i n the laboratory, where the supply of food i s regular, the type of food i s less variable, and the concentration of food i s greater. Based upon the study, the developmental stages of j aponica and C. plumchrus occupy two different trophic l e v e l s . A p i c t o r i a l repre-sentation of the l i n k s of the food chain among these animals i s shown below: Trophic l e v e l I Trophic l e v e l II Trophic l e v e l I I I = Primary productivity = Herbivorous n a u p l i i = Herbivorous copepodites = Carnivorous copepodites Although the developmental stages belong generally to two trophic l e v e l s , the size range of food p a r t i c l e s preferred by each developmental stage, the seasonal and d i e l d i s t r i b u t i o n , and the occurrence of these animals i n the sea are different. By virtue of these differences, the various developmental stages of japonica and C^_ plumchrus manage to co-exist i n the same environment. 76 BIBLIOGRAPHY Anraku, M., and Omori, M. , 1963. P r e l i m i n a r y survey of the r e l a t i o n s h i p between the fe e d i n g h a b i t and the s t r u c t u r e of the mouth p a r t s of marine copepods: Limmo. Oceanog. 8^ . 116-116. Ar a s h k e v i c h , ye. G. , 1968. 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Pro d u c t i o n s t u d i e s i n the S t r a i t of Georgia. P a r t I I . Secondary p r o d u c t i o n under the F r a s e r R i v e r plume, February to May, 1967: J . Exp. Mar. B i o l . E c o l . 3_, 39-50 P e t i p a , T. S., 1959. Feeding of the copepod A c a r t i a c l a u s i i : Trans. Sevastopol. B i o l . S t . Acad. S c i . U.S.S.R. H , 72-100. P i c k a r d , G. L., 1961. Oceanographic f e a t u r e s of I n l e t s i n the B r i t i s h Columbia mainland c o a s t : J . F i s h . Res. Bd. Canada, 18_ (16), 907-999. P r o v o s o l i , L., 1968. Composition of P r o v o l s o l i s 'ES' enrichment s o l u t i o n : Marine B i o l o g y , Marine B a c t e r i o l o g y , Ed. C. H. Oppenheimer, The N. Y. Academy of S c i ences, N. Y. V o l . 4. Raymont, J . E. G., and Gross, F., 1941. On the f e e d i n g and breeding of Calanus  f'inmarchicus under l a b o r a t o r y c o n d i t i o n s : Proc. Roy. Soc. Edinburgh,, 61 , 261-287. Sheldon, R. W., and Parsons, T. R., 1967. A continuous s i z e spectrum f o r p a r t i c u l a t e matter i n the sea; J . F i s h . Res. Bd. Canada, 2 4 ( 5 ) , 909-915. Simpson, G. G., and Beck, W. S., 1957. L i f e , an I n t r o d u c t i o n to Biology,; Second e d i t i o n . Harcourt, Brace and World, I n c . , pg. 110. Slo b o d k i n , L. B. , 1968. How to be a predator: Am. Z o o l . 8_(1), 43-51. Tanaka, 0., 1956. The p e l a g i c copepods of the IZU r e g i o n , middle Japan, Systematic account, 1. F a m i l i e s Calanidae and Eucalanidae: Pub. of the Seto Mar. B i o l . Lab. V o l V, No. 2, 255-257. Wickstead, J . H., 1962. Food and feeding i n p e l a g i c copepods: Proc. Z o o l . Soc. Lond. 139(4), 545-555. Wimpenny, R. S., 1938. P i u r n a l v a r i a t i o n i n the fee d i n g and breeding of zooplankton r e l a t e d to the numerical balance of the zoo-phytoplankton community: J . Cons. I n t . E x p l o r . Mer., 13, 323. APPENDIX A Morphology of the developmental stages of Euchaeta  j aponica Marukawa and Calanus plumchrus Marukawa. 79 Figure 1. Naupliar stages of japonica A - F i r s t nauplius B - Second nauplius C - Third nauplius D - Fourth nauplius E - F i f t h nauplius F - Sixth nauplius Figure 2. F i r s t Antennae of the naupliar stages of E. japonica A - F i r s t nauplius B - Second nauplius C - Third nauplius D - Fourth nauplius E - F i f t h nauplius F - Sixth nauplius Fid. 2 81 Figure 3. Second antennae of the naupliar stages of E. japonica t A - F i r s t nauplius B - Second nauplius C - Third nauplius D - Fourth nauplius E - F i f t h nauplius F - Sixth nauplius r«6i-3 82 Figure 4. Mandibles of the naupliar stages of E. japonca A - F i r s t nauplius B - Second nauplius C - Third nauplius D - Fourth nauplius E - F i f t h nauplius F - Sixth nauplius G - F i r s t maxilla H - Second maxilla I - Maxilliped of the s i x t h nauplius Flft. 5" 83 Figure 5. Copepodite stages of Euchaeta japonica A - F i r s t copepodite B - Second copepodite C - Third copepodite D - Fourth copepodite E - F i f t h copepodite F - Sixth copepodite - male G - Sixth copepodite - female Figure 6. F i r s t antennae of the copepodites of E. japonic A - F i r s t copepodite B - Second copepodite C - T h i r d copepodite D - Fourth copepodite E - F i f t h copepodite - male F - F i f t h copepodite - female G - S i x t h copepodite - male H - S i x t h copepodite - female 85 Figure 7. Second antennae of the copepodites of E. j aponica A - F i r s t copepodite B - Second copepodite C - Third copepodite D - Fourth copepodite E - F i f t h copepodite - male F - F i f t h copepodite - female G - Sixth copepodite - male H - Sixth copepodite - female FlGi.1 86-Figure 8. Mandibles of the copepodites of E. japonica A - F i r s t copepodite B - Second copepodite C - Third copepodite D - Fourth copepodite E - F i f t h copepodite - male F - F i f t h copepodite - female G - Sixth copepodite - male H - Sixth copepodite - female Fie, • S < 87 Figure 9. F i r s t maxillae of the copepodite stages of E. japonica A - F i r s t copepodite B - Second copepodite C - Third copepodite D - Fourth copepodite E - F i f t h copepodite - male F - F i f t h copepodite - female G - Sixth copepodite - male H - Sixth copepodite - female FiGi °[ Figure 10. Second maxillae of the copepodite stages of E. japonica A - F i r s t copepodite B - Second copepodite C - Third copepodite D - Fourth copepodite E - F i f t h copepodite - male F - F i f t h copepodite - female G - Sixth copepodite - male H - Sixth copepodite - female LL. 89 Figure 11. M a x i l l i p e d s of the copepodite stages of E. j a p o n i c a A - F i r s t copepodite B - Second copepodite C - T h i r d copepodite D - Fourth copepodite E - F i f t h copepodite - male F - F i f t h copepodite - female G - S i x t h copepodite - male H - S i x t h copepodite - female Figure 12. N a u p l i a r stages of C. plumchrus A - F i r s t n a u p l i u s B - Second naupli u s C - T h i r d n a u p l i u s D - Fourth n a u p l i u s E - F i f t h n a u p l i u s F - S i x t h n a u p l i u s Figure 13. F i r s t antennae of the naupliar stage C. plumchrus A - F i r s t nauplius B - Second nauplius C - Third nauplius D - Fourth nauplius E - F i f t h nauplius F - Sixth nauplius c D t-ISi. 13 F i g u r e 14. Second antennae of the n a u p l i a r stages of C. plumchrus A - F i r s t n a u p l i u s B - Second naupli u s C - T h i r d n a u p l i u s D - Fourth n a u p l i u s E - F i f t h n a u p l i u s F - S i x t h n a u p l i u s Figure 15. Mandibles of the n a u p l i a r stages of C. plumchrus A - F i r s t n a u p l i u s B - Second n a u p l i u s C - T h i r d nauplius D - Fourth n a u p l i u s E - F i f t h n a u p l i u s F - S i x t h nauplius Figure 16. A - F i r s t m a x i l l a of the f i f t h n a u p l i u s of C. plumchrus B - F i r s t m a x i l l a C - Second m a x i l l a D - M a x i l l i p e d of the s i x t h n a u p l i u s of plumchrus 95 Figure 17. Copepodite stages of Calanus plumchrus A - F i r s t copepodite B - Second copepodite C - Third copepodite D - Fourth copepodite E - F i f t h copepodite F - Sixth copepodite - male G - Sixth copepodite - female n 96 Figure 18. F i r s t antennae of the copepodite stages of C. plumchrus A - F i r s t copepodite B - Second copepodite C - T h i r d copepodite D - Fourth copepodite E - F i f t h copepodite F - S i x t h copepodite - male G - S i x t h copepodite - female 97 Figure 19. Second antennae of the copepodite stages of C. plumchrus A - F i r s t copepodite B - Second copepodite C - Third copepodite D - Fourth copepodite E -. F i f t h copepodite F - Sixth copepodite - male G - Sixth copepodite - female F\6{- H 98 Figure 20. Mandibles of the copepodite stages of C. plumchrus A - F i r s t copepodite B - Second copepodite C - Third copepodite D - Fourth copepodite E - F i f t h copepodite F - Sixth copepodite - male G - Sixth copepodite - female 99 Figure 21. F i r s t maxillae of the copepodite stages of C. plumchrus A - F i r s t copepodite B - Second copepodite C - Third copepodite D - Fourth copepodite E - F i f t h copepodite F - Sixth copepodite - male G - Sixth copepodite - female h f c - 2 1 100 Figure 2 2 . Second m a x i l l a e of the copepodite stages of C. plumchrus A - F i r s t copepodite B - Second copepodite C - Th i r d copepodite D - Fourth copepodite E - F i f t h copepodite F - S i x t h copepodite - male G - S i x t h copepodite - female A B FiGn.2-2 Figure 23. Maxillipeds of the copepodite stages of C. plumchrus A - F i r s t copepodite B - Second copepodite C - Third copepodite D - Fourth copepodite E - F i f t h copepodite F - Sixth copepodite - male G - Sixth copepodite - female i j i i i P f - T T i i - } F l G i - E 3 . 102 APPENDIX A Morphology of the developmental stages of Euchaeta japonica Marukawa and  Calanus plumchrus Marukawa: Euchaeta j aponica and Calanus plumchrus were o r i g i n a l l y described by Marukawa (1921) from the Sea of Japan and Ochotsk Sea, respectively. But, E. japonica has since been recorded from the Straight of Georgia (Campbell 1929, 1930, 1934a and Fulton 1968) and from the North East P a c i f i c by C. Davis (1949) and C. plumchrus from the S t r a i t of Georgia (Campbell 1929, 1930, 1934a and Fulton 1968). Marukawa (1921) points out that E^ japonica i s similar to E.  norvegica Boeck, recorded from North A t l a n t i c and Polar seas. These two d i f f e r however, i n the nature of the l a s t free thoracic segment, the geni t a l protuberance and by the armature on the outer surface of the proximal segment of the exopod of the f i r s t swimming leg. Calanus plumchrus Marukawa has been recognised as i d e n t i c a l with Calanus tonsus Brady u n t i l Nakai informed (personal communication) Tanaka (1954) that C_;_ tonsus of the Antarctic was d i s t i n c t from C_^  tonsus (C.  plumchrus) of the North P a c i f i c . C. tonsus Brady d i f f e r s from C. plumchrus i n the nature of the genital segment, by the presence of d i s t i n c t teeth on the cutting edge of the mandible, by the possession of spines on the proximal inner lobe of the f i r s t maxilla and by the presence of a row of short spines on the d i s t a l inner surface of the baseipod of the second to f i f t h legs (Tanaka 1956) . Marshall recognised C_^_ plumchrus Marukawa as a variety of C. tonsus under the name of C^ tonsus var. plumchrus which has one pair of conspicuously long, plumose caudal setae. Brodsky (1948, 1950) however, considered the forms i n the North P a c i f i c Ocean as C. tonsus and divides them into two groups: C^ tonsus f. plumchrus (C. plumchrus) which has very long setae on the caudal furca and C. tonsus f. typica which has short setae. 103 Terminology: The term 'cephalothorax' refers to the fused cephalon (head) and the f i r s t thoracic segment which bears the maxilliped. The term 'free thoracic segments' refers to the segments of the thorax not fused with the head. The term 'prosome' refers to the cephalothorax and free thoraxic segments and the term 'urosome' to the genital segment and abdomen. The term 'anal segment' refers to the l a s t urosomal segment which bears the anal opening and the caudal rami which are two appendage-like structures attached to the anal segment. The terms 'coxa, basipod, protopod, endopod, exopod and epipod are used according to Marshall and Orr (1955) . The terms 'inner' and 'outer', with regard to the appendages, refer respectively to the surfaces closest to and furthest from the median longitudinal axis of the body of the copepod. The term 'seta' refers to a slender, f l e x i b l e , armature element that may or may not be plumose; 'setule' refers to a small seta; and 'spines' refer to s t i f f , sharply pointed or bluntly-tipped armature element. DESCRIPTION Morphology of the developmental stages of E. japonica:  Eggs. The eggs are dark blue i n colour. The diameter of an egg ranges from 0.29 to 0.31 mm., with an average of 0.30 mm. based on 20 specimens. Nauplius I. (Fig. 1A) The length of the animal ranges from 0.57 to 0.61 mm., with an average of 0.59 mm. based on 10 specimens. The body i s blue i n colour and oval i n shape with a blunt posterior end. I t contains a large amount of yolk i n the form of droplets. There are three pairs of appendages on the anterior end of the body. The labrum i s conspicuous on the ventral surface of the body. The f i r s t antenna (Fig. 2A) i s a uniramous appendage with three 104 segments. The proximal segment Is broader than i t i s long and carries no armatue. The middle segment i s longer than i t i s broad and carries three setae. The f i r s t and second setae are small and t h i n , situated one-third and two-thirds of the distance, respectively, from the proximal end. The t h i r d seta i s large and located at the upper inner surface of the segment. The d i s t a l segment i s almost three times as long as the proximal segment and carries three setae at the terminal rounded end. The second antenna (Fig. 3A) i s a biramous appendage. The coxa and the basipod are not separated. The endopod i s two-segmented, the proximal segment of which i s not separated from the basipod. The proximal segment i s longer than i t i s broad and carries a t i n y seta on the upper inner surface. The d i s t a l segment i s almost half as long as the proximal segment and i s broad at the base and narrow at the top. There i s a small seta at the middle of the segment on the inner surface and two setae terminally. The exopod i s five-segmented, of which the proximal segment i s incompletely separated from the basipod as well as from the second proximal segment. The segments one to four each carries a single large seta on the upper inner surface, and the most d i s t a l segment carries two setae terminally. The mandible (Fig. 4A) i s a biramous appendage. The coxa and the basipod are d i s t i n c t l y separated. They are more or less quadrangular i n shape. The coxa i s without armature whereas the basipod has a t i n y spine on the curved surface. The endopod i s single-segmented and elongated. I t carries two small setae on the inner surface on two s l i g h t elevations and two setae on the rounded terminal end. The exopod i s four-segmented. The d i s t a l segment i s longer than i t i s broad and the rest of the segments are broader than they are long. Each of the f i r s t three segments from the d i s t a l end carries a single large seta on the upper inner surface, and the most d i s t a l segment carries two setae terminally. 105 Nauplius I I . (Fig. IB) The length of the animal ranges from 0.59 to 0.65 mm., with an average of 0.63 mm. based on 10 specimens. The animal i s blue i n colour. The body i s more oval i n shape than the N/1 stage. The posterior end i s s l i g h t l y elongated and carries a pair of small setae. The three pairs of appendages are well developed. The morphology of the mouth parts of the naupliar stages N/2 to N/6 of E. japonica i s more or less s i m i l a r to that of the N/1 stage. There-fore, only the differences are mentioned i n the following paragraphs. The f i r s t antenna (Fig. 2B) bears four terminal setae on the d i s t a l segment. On the second antenna (Fig. 3B) the l i n e / of demarcation of the coxa and the basipod begins to appear. The endopod carries three terminal setae. The proximal segment of the exopod i s completely separated from the basipod and the second segment of the exopod. The endopod of the mandible (Fig. 4B) bears three setae terminally. Nauplius I I I (Fig. IC) The length of the animal ranges from 0.63 to 0.67 mm., with an average of 0.65 mm. based on 10 specimens. I t i s oval i n shape and s l i g h t l y more elongated than the N/2 stage. The posterior end i s prominently narrowed and bears a pair of long setae. The segments of the f i r s t antenna (Fig. 2C) are s l i g h t l y longer and the most d i s t a l segment carries s i x setae terminally and two tiny spine-l i k e projections on the upper outer surface. The coxa of the second antenna (Fig. 3C) i s d i s t i n c t . The mandible (Fig. 4C) has an additional slender seta on the inner surface of the f i r s t segment of the endopod. Nauplius IV (Fig. ID) The length of the animal ranges from 0.65 to 0.70 mm., with an average of 0.67 mm. based on 20 specimens. The body i s pale blue i n colour. 106 It i s more elongated than the N/3 and i s provided with the three pairs of appendages. The d i s t a l segment of the f i r s t antenna (Fig. 2D) i s more elongated and carries eight long setae and one spine-like seta along the fringe of the terminal end. The exopod of the second antenna (Fig. 3D) i s six-segmented of which the proximal segment i s incompletely separated from the second seg-ment and i t carries one long and one short spine-like setae. The segments two and f i v e each carries a single seta and the most d i s t a l segment carries two long setae and a tiny one terminally. On the mandible (Fig. 4D) there i s an indication for the formation of the teeth on the inner surface of the coxa. The short seta on the inner surface of the endopod of the N/3 i s larger i n the N/4 stage. Nauplius V (Fig. IE) The length of the animal ranges from 0.77 to 0.82 mm., with an average of 0.79 mm. based on 20 specimens. The body s t i l l contains a l o t of o i l droplets and the colour i s pale blue. The f i r s t maxillae are formed as buds on the ventral surface of the body. The coxa of the f i r s t antenna (Fig. 2E) i s broader than i t i s long and without any setae. The basipod i s also broader than i t i s long and carries two short setae and one thick seta on the outer surface and four terminal setae, three are thick and one i s t h i n . On the second antenna (Fig. 3E) the proximal small seta on the inner surface of the endopod and the t h i r d small terminal seta of the d i s t a l segment of the exopod are longer. The teeth on the inner surface of the coxa of the mandible (Fig. 4E) are more prominent than i n the N/4 stage. The endopod shows indication of segmentation. The f i r s t maxilla of the f i f t h nauplius i s very small l i k e a protuberance. 107 Nauplius VI (Fig. IF) The length of the animal ranges from 0.80 to 0.96 mm. with an average of 0.9 mm. based on 25 specimens. The animal i s more elongated than the N/5 stage and the posterior end shows indication of segmentation. The maxillipeds are shown as two elongated lobes on the ventral side. On the f i r s t antenna (Fig. 2F) , the small tenth seta on the' outer surface of the terminal segment i s longer than i n the N/5 stage. The terminal segment of the endopod of the second antenna (Fig. 3F) carries one additional seta to the three already present i n the N/5 stages and another additional seta on the inner surface of the same segment. The most d i s t a l segment of the exopod i s d i s t i n c t l y divided unlike i n the N/5 stage. The teeth on the inner surface of the coxa of the mandible (Fig. 4F) are well developed. The maxilla (Fig. 4G) appears as a bilobed structure carrying a few setae terminally. The second maxilla (Fig. 4H) i s very small and lobe-like i n shape. I t consists of a series of convex surfaces on the inner surface which carry small setules. The maxilliped (Fig. 41) i s a long lobe-like appendage carrying a pair of setae terminally. Copepodite I (Fig. 5A) The length of the animal from the anterior end of the cephalothorax to the posterior end of the caudal rami, excluding the setae, ranges from 1.0 to 1.2 mm., with an average of 1.0 mm. based on 10 specimens. They are transparent with orange coloured o i l globules i n the body. The body i s broader than i t i s long. The cephalothorax i s narrow an t e r i o r l y and broad posterio r l y . I t bears the mouth parts on the ventral surface. The cepha-lothorax i s followed by three free thoracic segments carrying two pairs of swimming legs. The cephalothorax and the free thoracic segments constitute the body of the animal. The body i s followed by the urosome (abdomen) which consists of two segments. The second segment i s larger than the f i r s t . 108 The f i r s t antenna (Fig, 6A) i s uniraraous and extends up to the posterior end of the animal. I t consists of ten segments of which, the fourth segment i s almost twice as long as the second segment. The second antenna (Fig. 7A) i s a biramous appendage. The coxa bears a small plumose seta on the inner surface; the basipod i s large with two slender setae on the upper inner surface; the endopod i s two-segmented of which the proximal segment i s s l i g h t l y longer than the d i s t a l one. The proximal segment bears two plumose setae on the inner surface towards the d i s t a l end and the d i s t a l segment bears three plumose setae on the inner surface and f i v e plumose setae terminally. The exopod i s seven-segmented. The most proximal segment i s short, the second segment i s quadrate with a f i n e setae on the d i s t a l inner surface. The segments three to s i x are short and each of these i s provided with a very fine seta on the d i s t a l inner surface; . the most d i s t a l segment i s longer than the second segment and bears one slender seta on the inner surface and three setae terminally. The mandible (Fig. 8A) i s biramous. The coxa consists of a single segment, which carries a series of small conspicuous teeth. The basipod i s quadrangular and carries a small, naked seta on the inner surface. The endopod i s two jointed. The proximal segment bears a single plumose seta on the upper inner surface. The proximal segment i s provided with four plumose setae terminally. The exopod i s s l i g h t l y longer than the endopod and i s five-segmented. A l l the segments of the exopod are broader than they are long. The segments one to four each carries one plumose seta and the most d i s t a l segment carries two plumose setae terminally. The f i r s t maxilla (Fig. 9A) consists of lobes. The coxa consists of a large gnathobase, a small in t e r n a l lobe and a large external lobe on the epipod. The gnathobase bears f i v e spinous setae and four plumose setae; the small internal lobe carries one long, slender plumosed seta and the 109 epipod carries four long, plumosed setae. The endopod consists of three segments. The proximal large segment of the endopod carries a single, long plumosed seta; the middle segment i s imperfectly divided from the d i s t a l segment and i t bears one long and one short plumose setae and the d i s t a l segment bears one short, naked seta and two long, s l i g h t l y serrated setae. The exopod i s single-segmented and carries seven plumose setae. The second maxilla (Fig. 10A) i s a small appendage consisting of a series of lobes. The coxa and the basipod are not d i s t i n c t l y separated. The coxa consists of four lobes of which the proximal three lobes are small. The most proximal lobe carries two long plumose setae and one t i n y spine-l i k e seta. The lobes two to four bear three setae each. One of the three setae i s short and two are long and provided with plumosities. The upper portion of the appendage carries a bunch of f i v e setae, of which three are provided with a few fine plumosities and the other two are provided with thick plumosities. The coxa of the maxilliped (Fig. 11 A) i s longer than i t i s broad and carries f i v e setae i n three groups on the inner surface. The f i r s t one arises from one t h i r d of the distance from the proximal end and i s spiny i n nature; the second group consists of two setae which are spiny a r i s i n g from the middle of the segment and the t h i r d group consists of two spiny setae which arise from the d i s t a l end of the segment. The basipod i s as big' as the coxa and bears two setae along the middle of the segment on the inner surface. One of the two setae i s spiny and the other i s plumose. The terminal part of the appendage consists of three i n d i s t i n c t segments. The proximal one i s provided with a setule and the middle one with a single naked seta and the d i s t a l segment with four naked setae. The description of the mouth parts of the rest of the copepodite stages carries only the differences from those of the f i r s t copepodite stage. 110 Copepodite I I (Fig. 5B) The body i s more transparent than the C/l and contains o i l droplets. The length of the animal from the anterior end of the cephalothorax to the posterior end of the anal furca, excluding the setae, ranges from 0.9 to 1.3 mm., with an average of 1.1 mm. based on 20 specimens. The cephalothorax i s broader and carries three pairs of swimming legs. The d i s t a l segment of the urosome i s longer. The f i r s t antenna (Fig. 6B) consists of 12 segments. The second antenna (Fig. 7B) i s si m i l a r to that of the C/l stage. The coxa of the mandible (Fig. 8B) bears more teeth than that of the C/l stage. The d i s t a l segment of the endopod carries f i v e setae terminally. The f i r s t maxilla (Fig. 9B) consists of protopod, epipod, endopod and the exopod. The gnatho-base of the protopod i s provided with f i v e stout setae with spines and f i v e plumose setae. The epipod bears f i v e setae and the exopod carries seven setae. The endopod consists of three segments, the proximal segment of which bears three setae; the middle segment bears two setae and the d i s t a l segment bears three setae. On the second maxilla (Fig. 10B) the short seta on the f i r s t lobe i s grown longer and i s provided with spines. The coxa of the maxilliped (Fig. 11B) bears a slender seta at the proximal outer surface and two spinous setae on the proximal inner surface. There are two setae at the d i s t a l inner surface, one of which i s plumose and the other i s spinous i n nature. There are two setae at the middle inner surface of the segment, one of these i s smooth and the other i s spinous. The terminal portion of th i s appendage consists of three segments. The proximal segment carries two thick, long setae and one thin plumose setae; the middle segment carries one thick seta and the terminal segment carries three thick, long setae and one thin plumose seta. I l l Copepodite I I I (Fig. 5C) The length of the animal ranges from 2.0 to 2.4 mm., with an average of 2.3 mm., based on 10 specimens. The mouth parts on the ventral surface of the cephalothorax have a l i g h t reddish tinge. There are four pairs of swimming legs. The urosome i s si m i l a r to that of.the C/2 stage. The f i r s t antenna (Fig. 6C) i s 16 segmented, of which the t h i r d i s imperfectly divided into four. The second antenna (Fig. 7C) i s s i m i l a r to that of the C/2 stage except for the following differences; the proximal segment of the endopod i s twice as long as the d i s t a l segment. The d i s t a l segment bears ten setae in groups of two. The second and the seventh seg-ments of the exopod aire s l i g h t l y more elongated than those i n the C/2 stage. The mandible (Fig. 8C) i s s l i g h t l y bigger. The d i s t a l segment of the endopod carries six setae and the teeth are numerous and stronger than those i n the C/2 stage. The gnathobase of the f i r s t maxilla (Fig. 9C) carries f i v e thick setae with short spines and f i v e plumose setae. The exopod carries seven •plumose setae i n a group and a single one on the outer surface. The epipod carries one short and six well developed plumose setae. The spines on the second maxilla (Fig. 10C) are stronger on the setae than those i n the C/2 stage. The coxa of the maxilliped (Fig. 11C) bears three sets of thick, spinous setae on the inner surface. The proximal group consists of two setae, one of which i s stouter and stronger than the other; the second group consists of three with one strong and two short setae with spines; the th i r d group i s located at the d i s t a l end of the segment and one of the three setae i s spinous. The basipod carries three setae almost at the middle of the segment. The proximal seta of this group i s strong and spinous. The middle seta i s very small, thin and non-spinous; and the d i s t a l 112 seta i s strong but non-spinous. Copepodite IV (Fig. 5D) The length of the animal ranges from 3.9 to 4.3 mm., with an average of 4.0 mm. based on 20 specimens. The reddish tinge on the bases of the mouth parts i s s l i g h t l y darker than i s observed i n the C/3 stage. The sex-of the animal i s d i f f e r e n t i a t e d at this stage by the presence of the r u d i -mentary f i f t h pair of legs i n the male. The f i r s t antenna (Fig. 6D) i s 21 segmented with the ninth segment incompletely divided into three. The d i s t a l segment of the endopod of the second antenna (Fig. 7D) carries 10 setae. The coxa of the mandible (Fig. 8D) i s provided with much stronger teeth than those i n the e a r l i e r stages. There i s a s i n g l e , long spinous seta along with the teeth. The d i s t a l segment of the endopod carries seven setae terminally instead of the six i n the C/3 stage. The gnathobase of the f i r s t maxilla (Fig. 9D) carries nine strong, spinous setae, four thin setules and one plumose seta. There are nine plumose setae on the exopod and seven well-developed setae on the epipod. The d i s t a l segment of the endopod bears two strong, serrated setae and the proximal seg-ment bears one seta and the middle segment carries three setae. In between the endopod and the gnathobase there are two in t e r n a l lobes, each carrying a single plumose seta. . The most d i s t a l segment of the second maxilla (Fig. 10D) carries six setae terminally, one of which i s provided with l a t e r a l spines. The maxilliped (Fig. 11D) bears three groups of setae on the coxa, of which the proximal group consists of two setae. The proximal seta of the proximal group i s toothed and the other i s provided with large spines on the lower end of the setae and small spines the d i s t a l end of the seta. The d i s t a l seta of the middle group i s spinous whereas the other two setae are toothed. The d i s t a l 113 group of setae on the coxa are strong but without spines or plumosities. There are three setae on the basipod, of which the middle one i s short with a broad base; the setae l a t e r a l to the middle one are fine-toothed. The d i s t a l part of the appendage i s five-segmented. The proximal segment carries three thick plumose setae and one thin plumose seta; the second segment carries one long, thick seta and one thin seta; the t h i r d segment carries one thick seta; the fourth segment carries one thick and one thin seta and the d i s t a l segment carries two thick and two thin setae. Copepodite V (Female) (Fig. 5F) The length of the animal ranges from 5.4 to 5.7 mm., with an average of 5.4 mm. based on 25 animals. The bases of the mouth parts have a s l i g h t l y dark-reddish tinge. The body i s robust and carries four pairs of swimming legs. The urosome consists of four segments. The f i r s t antenna (Fig. 6F) i s 23 segmented. The d i s t a l segment of the endopod of the second antenna (Fig. 7F) carries 13 setae terminally. The d i s t a l segment of the endopod of the mandible (Fig. 8F) carries eight plumose setae. The gnathobase of the f i r s t maxilla (Fig. 9F) carries eight strong setae with spines and four thin setae. The basal segment of the endopod i s provided with two long and two short setae and one very short seta; the second segment i s provided with one seta on the inner surface and the d i s t a l segment carries three setae terminally. The exopod carries 10 plumose setae, and the epipod carries seven setae. The second maxilla (Fig. 10F) i s the same as for the C/4 stage. The coxa of the maxilliped (Fig. 11F) i s with three groups of setae. The proximal group has two short setae and one spinous seta, and the middle group with one spinous seta, one t h i n , long seta and one short seta; the proximal segment of the d i s t a l portion i s provided with three stout setae and two thin setae; the second and the t h i r d segments are provided with one stout 114 seta and one thin seta; the fourth segment with one seta with spines, one stout seta and one thin seta and the f i f t h segment i s provided with one seta with spines, one stout, one t h i n , long seta and one short seta. Copepodite V (Male) (Fig. 5E) A l l the mouth appendages i n the male animal (Figs. 6E to HE) of the C/5 stage are similar to those i n the C/5 female. Copepodite VI (Female) (Fig.'5H) The length of the animal ranges from 4.4 to 5.99 mm., with an average of 5.33 mm. based on 10 specimens. The anterior end of the cepha-thorax carries a single rostrum of 0.13 mm. long and a f r o n t a l organ (a group of sensory c e l l s ) bearing one or two minute papil l a e . The free thoracic segments carry four pairs of swimming legs on the ventral surface. The postero-lateral margins of the l a s t segment of the prosome are provided with t u f t s of fine plumosities. The prosome i s followed by the urosome which consists of four segments. The f i r s t segment of the urosome i s the symmetrical, genital segment. Ventrally, the segment bears a protuberance with a notch in the centre. The apical part of the protuberance has a broad, round l i p , fringed with very short plumosities. The second through the fourth segments are denticulated along the postero-lateral margins and are fringed with plumosities along the l a t e r a l margins. The caudal rami are nearly twice as long as they are broad, i n dorsal view. Each ramus bears a small seta and fine plumosities on the outer surface, four long plumose seta on the d i s t a l end and fine plumosities on the inner surface. The f i r s t antenna (Fig. 6H) consists of twenty-four segments. There are a few aesthetascs on the outer surface of the segments and closely arranged, short plumosities on the inner surfaces of segments two through eleven. The terminal segment carries f i v e unequal non-plumose setae d i s t a l l y . The coxa of the second antenna (Fig. 7H) bears a small, plumose seta 115 and the basipod bears two slender, subequal setae on the inner surface. The long seta on the basipod reaches the middle of the f i r s t segment of the endopod which i s two segmented. The proximal segment of the endopod carries two setules on the d i s t a l inner surface. The second segment of the seven segmented exopod carries a short, plumose seta on the inner d i s t a l surface. The seventh segment carries a plumose seta from the middle of the segment sub-marginally. The two endopod segmented of the mandible (Fig. 8H) bears a sin g l e , long, naked seta on the inner surface of the proximal segment and nine plumose setae at the terminal end of the d i s t a l segment. The f i r s t maxilla (Fig. 9H) i s a complicated structure. The gnathobase i s armed with eight stout and f i v e slender plumosities and the epipod bears seven long and two short plumose setae. The endopod carries six long plumose setae on the inner surface and the exopod carries eight plumose setae. There are two small lobes located between the gnathobase and the endopod, each carrying a single long plumose seta. The second maxilla (Fig. 10H) i s an uniramous structure with a proximal single segmented protopod and an i n d i s t i n c t l y segmented endopod (Marshall, 1955) . The protopod carries two groups of seven spinous setae on the d i s t a l half of the inner surface. The i n d i s t i n c t l y segmented endopod bears several clusters of three plumose setae a r i s i n g from a knob-like projection along the inner surface as well as a cluster of f i v e denticulated plumose setae on the d i s t a l surface. The maxilliped (Fig. 11H) i s s i m i l a r to that of the C/5 stage. A cluster of thin plumosities arise from the base of the middle group of setae on the coxa. The proximal inner surface of the basipod i s l i n e d with small plumosities directed backwards. In addition, there i s a group of spines medial to these plumosities. The d i s t a l inner surface of the segment i s lined by 116 long plumosities. The most proximal segment of the f i v e segmented endopod carries s i x unequal plumose setae, the second carries three unequal plumose setae, the t h i r d 2 unequal setae, the fourth 4 unequal plumose setae, and the d i s t a l segment carries three unequal setae of which the longest i s denticulated and the rest are non-plumose. , Copepodite VI (Male (Fig. 5G) The length of the animal ranges from 4.8 to 5.99 mm. with a mean of 5.2 mm. based on nine specimens. The postero-lateral projection of the l a s t free thoracic segment of the prosome are more rounded than pointed. The urosome i s f i v e segmented, of which the second i s the largest and the f i f t h segment i s the smallest. The dorso-posterior margins of the second, the t h i r d , and the fourth segments are denticulated. The candal rami are long as they are broad and are provided with short plumosities along the inner surface. Each ramus carries f i v e plumose setae terminally, of which the second seta from the inner end i s short and curved. The f i r s t antenna (Fig. 6G) i s twenty-two segmented and i t projects a l i t t l e beyond the posterior end of the second segment of the urosome. The l i n e of demarcation between the segments ten and eleven i s incomplete. The second antenna (Fig. 7G) shows the following differences from that of the female: The coxa bears no seta but the basipod bears a single, long, plumose seta. The proximal segment of the endopod bears no seta and the inner lobe of the d i s t a l segment bears seven plumose setae. The second and the seventh segments of the exopod are without setae on the inner surface. The gnathobase of the mandible (Fig. 8G) i s blunt without teeth. The basipod i s i n d i s t i n c t l y separated from the coxa. The f i r s t maxilla (Fig. 9G) i s a small, degenerated appendage. The gnathobase i s smooth. The proximal segment of the two segmented endopod 117 carries s i x slender plumose setae and the d i s t a l segment carries three long, plumose setae. The exopod carries eleven unequal, plumose setae and the epipod carries f i v e equally long, plumose setae. The two small lobes are completely l o s t . The second maxilla (Fig. 10G) i s a very small, unsegmented appendage with twelve plumose setae on the inner surface. The coxa of the maxilliped (Fig. 11G) bears a naked seta proximally on the inner surface, and right beneath i t there i s a small scalloped ridge. There are two more sets of plumose setae on the inner surface, of which the most proximal one i s at the d i s t a l t h i r d of the coxa and the other set i s on the d i s t a l surface. The endopod i s f i v e segmented with an indication of a small segment at i t s base. The fourth segment from the proximal end carries one plumose seta and the terminal segment carries three unequal plumose setae and two naked setae. Morphology of the developmental stages of Calanus plumchrus:  Eggs: The eggs of Calanus plumchrus are spherical, creamish white i n colour. The diameter of the egg ranges from 200 to 250 micron with an average diameter of 210 microns based on 20 eggs. Nauplius I (Fig. 12A) The length of the animal ranges from 0.22 to 0.25 mm. with an average of 0.23 mm. based upon 10 specimens. The f i r s t nauplius of C^ plumchrus i s cream i n colour. The body i s oval i n shape, with a rounded anterior end and a s l i g h t l y carrower posterior end. The posterior end carries a pair of thin setae. The animal bears three pairs of appendages, the f i r s t , and second antenna and the mandibles close to the anterior end. The f i r s t antenna (Fig. 13A) i s uniramous, elongated and a p i c a l l y s l i g h t l y rounded. I t consists of two segments. The proximal segment i s almost twice as long as the d i s t a l segment. The d i s t a l segment carries two 118 plumose setae terminally. The second antenna (Fig. 14A) i s more or less s i m i l a r to that of the corresponding stage of E^ j aponica. The endopod bears the only two d i s t a l setae. The exopod i s s i x segmented. The most proximal segment i s unarmed. The endopod of the mandible (Fig. 15A) bears two setae terminally. The exopod i s f i v e segmented. The segments two to four of the endopod are i n d i s t i n c t l y separated. The rest of the details are s i m i l a r to the mandible of the N/1 stage of E. japonica (Fig. 4A) . Nauplius I I (Fig. 12B) The length of the animal ranges from 0.25 to 0.31 mm., with an average of 0.30 mm. based on 25 specimens. The f i r s t antenna (Fig. 13B) i s three segmented. The proximal segment i s small; the middle segment bears three naked setae on the inner surface; the d i s t a l segment i s twice as long as the middle segment and carries three naked setae terminally. The second antenna (Fig. 14B) i s more or less s i m i l a r to that of the N/1 stage except that the four segments from the d i s t a l end of the exopod are completely separated from the most proximal segment. Nauplius I I I (Fig. 12C) The length of the animal ranges from 0.31 to 0.36 mm., with an average of 0.34 mm. based on 20 specimens. The body i s more elongated than that of the N/2 stage. The posterior part of the body i s d i s t i n c t from the anterior part and i s s l i g h t l y flexed v e n t r a l l y . There are two long and a few small setae at the posterior end of the body. The f i r s t antenna (Fig. 13C) consists of three segments. I t i s similar to that of the N/2 of plumchrus. The d i s t a l segment i s s l i g h t l y rounded of f . I t carries a small seta on the inner surface, two short setae on the outer surface and four setae terminally. The coxa and the basipod of the second antenna (Fig. 14C) are not 119 separated and are represented by knob-like projections. The proximal knob represents the coxa which carries three short plumose setae on the inner surface. The d i s t a l knob represents the basipod and carries two small and one long setae. The endopod i s two-segmented but the proximal segment i s not com- . p l e t e l y separated from the basipod. The incompletely separated segment of the endopod carries two t h i n , plumose setae on the inner surface. The d i s t a l segment of the endopod carries three t h i n , small plumose setae on the inner surface and four thick plumose setae terminally. The exopod i s seven-segmented but the most proximal segment i s not completely separated from the basipod and i t carries two small setae on the inner surface. The segments two to six carry one seta each on the inner surface, and the most d i s t a l segment carries three setae terminally. The mandible (Fig. 15C) i s a biramous appendage. The coxa i s broader than i t i s long. The basipod i s more or less quadrangular and carries four t h i n , small plumose setae on the inner surface. The endopod carries a group of four small plumose setae at about one t h i r d distance from the proximal end; a set of two setae at about two-thirds the distance from the lower end and a set of two setae at about two-thirds the distance from the lower end and a set of four setae at the terminal end of the segment. The exopod i s s i m i l a r to that of the N/2 stage except that the setae i n the N/3 stage are provided with plumosities. Nauplius IV (Fig. 12D) The length of the animal ranges from 0.40 to 0.52 mm., with an average of 0.45 mm. based on 20 specimens. The body i s transparent and carries a large o i l drop. The body i s broad anteriorly and narrow posteriorly. The posterior end represents the abdomen which i s flexed. The abdomen carries a pair of denticulate setae and four pairs of thin setae. There are two pairs of denticulate setae v e n t r a l l y on the abdomen. 120 The f i r s t antenna (Fig. 13D) has more setae than that of the N/3 stage and they have plumosities. The middle segment carries three plumose setae on the inner surface and the d i s t a l segment carries three plumose setae on the inner surface, four on the outer surface and four terminally. The second antenna (Fig. 14D) i s similar to that of the N/3 stage except that the setae are longer and thicker. The mandible (Fig. 15D) i s better developed than the N/3 stage. The coxa bears a few small teeth on the inner surface. The basipod carries f i v e long plumose setae; the endopod carries seven long setae on the inner surface and four long setae terminally. The exopod i s same as the N/3. The f i r s t maxilla appears as a tiny bilobed structure. Nauplius V (Fig. 13E) The length of the animal ranges from 0.53 to 0.56 mm., with an average of 0.54 mm. based on 10 specimens. The body i s more transparent and the dorso-ventral flecture of the abdomen i s more pronounced. The f i r s t antenna (Fig. 13E) i s more or less si m i l a r to that of the N/4 stage. The proximal segment has one plumose seta, the middle segment has two plumose setae and the d i s t a l segment has four plumose setae on the inner surface, seven on the outer surface and four terminally. The mandible (Fig. 15E) i s si m i l a r to that i n the N/4 stage except that the teeth on the gnathobase are more d i s t i n c t than i n the N/4 stage. The f i r s t maxilla (Fig. 16A) i s a small appendage but i s better developed than that i n the N/4 stage. The gnathobase has a smaller inner projection without any setae. The coxa bears a pair of slender setae. The basipod which i s i n d i s t i n c t l y separated from the coxa bears two thin setae. The endopod i s i n d i s t i n c t l y separated from the basipod, and that carries two slender setae on the inner surface and four setae terminally. The exopod i s one-segmented and i s globular i n nature. I t bears f i v e setae along the 121 surface. Nauplius VI (Fig. 12F) The length of the animal ranged from 0.62 to 0.7 mm., with an average of 0.65 mm. based on 20 specimens. The body i s more elongated and the abdomen i s i n d i s t i n c t l y two-segmented. There are more spines at the terminal end of the abdomen than those are i n the case of the N/5 stage. The f i r s t antenna (Fig. 13F) i s five-segmented. The segments one to four are broader than they are long. The proximal segment i s without seta. The segments two to four each bears a long plumose seta on the upper inner surface. The d i s t a l segment i s fan-like and i s a l i t t l e more than double the length of a l l the f i r s t four segments together. I t bears f i v e setae on the inner surface, six on the outer surface, and four setae terminally. The second antenna (Fig. 14F) i s a biramous appendage. The coxa bears a small spine on the elevated inner surface and the basipod bears two small setae on the inner surface. The endopod i s two-segmented, of which the proximal segment i s broader than long and carries two short setae on the inner surface. The d i s t a l segment of the endopod i s longer than i t i s broad and i s provided with three setae on the middle inner surface and fi v e terminally. The exopod here i s exactly l i k e the exopod i n the N/5 stage. The mandible (Fig. 15F) i s same as the N/5 stage. The f i r s t maxilla (Fig. 16B) i s a complex, biramous appendage. The gnathobase i s more or less oval i n shape and i s provided with seven small spines on the inner surface. The two inner lobes each carries three setae and the epipod carries a single plumose seta. The endopod consists of two incompletely separated portions, of which the lower portion carries two setae, and the upper portion carries two setae on the inner surface and four terminally. The exopod i s single-segmented and carries three setae on the outer surface and four setae terminally. The second maxilla (Fig 16C) i s a small uniramous appendage. I t 122 consists of a series of small lobes. The f i r s t four lobes from the proximal end are provided each with two setae, and the f i f t h lobe carries three setae. The upper portion of this appendage carries four setae on the inner surface. The maxilliped (Fig. 16D) i s elongated and carries two long setae terminally. Copepodite I (Fig. 17A) The length of the animal ranges from 0.7 to 1.0 mm. with an average of 1.0 mm. based on 20 specimens. The animals are transparent. The body i s broader than i t i s long. The cephalothorax i s narrow an t e r i o r l y and broad posterio r l y . I t bears the mouth parts on the ventral surface. The cephalo-thorax i s followed by three free thoracic segments carrying two pairs of swimming legs. The thoracic segments are broader than they are long. The posterolateral margins of the l a s t thoracic segment are rounded. The cephalo-thorax together with the free thoracic segments constitute the prosome. The prosome i s followed by the urosome which consists of two segments. The proximal segment i s broader than i t i s long but the d i s t a l segment i s longer than i t i s broad. The f i r s t antenna (Fig. 18A) i s uniramous and i s eleven segmented. The penultimate segment from the d i s t a l end carries a short seta on the inner surface and the most d i s t a l segment carries one seta on the inner surface and two terminally. The second antenna (Fig. 19A) i s biramous. The coxa bears a short plumose seta and the basipod bears two plumose setae on the upper inner surface. The endopod consists of two segments. The proximal segment bears two th i n setae at the upper inner surface and the d i s t a l segment carries four on the inner surface and six terminally. The exopod consists of seven segments. The f i r s t and second segments from the proximal end carry each a pair of plumose setae, segments three to six carry each one plumose seta and the seventh 123 segment carries three plumose setae terminally and one l a t e r a l l y . The mandible (Fig. 20A) i s biramous. The inner surface of the coxa i s provided with numerous small teeth. The basipod i s large and carries four plumose setae on the lower inner surface. The endopod carries four setae at the lower inner surface, and six plumose setae terminally. The f i r s t maxilla (Fig. 21A) i s a complicated, small appendage. The gnathobase carries ten stout, spiny setae. The spines on those setae are short. There are two inner lobes between the gnathobase and the endopod. The proximal lobe carries four t h i n , plumose setae and the d i s t a l lobe carries three plumose setae. The endopod i s incompletely divided into three segments, of which, the f i r s t 2 segments each carries three thin plumose setae and the d i s t a l segment carries four plumose setae. The basipod carries three plumose setae on the inner surface. The exopod carries seven plumose setae and the epipod carries four stout, long plumose setae. The second maxilla (Fig. 22A) i s a very small, f l a t appendage, con-s i s t i n g of a series of lobes on the inner surface. Each lobe carries three plumose setae except the most d i s t a l lobe which carries four plumose setae, one of which i s thin and the other three are thick. The maxilliped (Fig. 23A) i s uniramous and consists of segments which are longer than they.are broad. The coxa carries a small plumose seta at the proximal inner surface, three i n the middle, and two at the d i s t a l end. The two of the. middle ones are stout and the other i s small. The basipod i s pro-vided with two thick plumose setae i n the middle of the segment. The d i s t a l portion of the maxilliped consists of two segments. The proximal segment of which i s longer than i t i s broad and i t i s almost three times the length of the d i s t a l segment. There are two thin setae on the proximal inner surface, one.thick plumose seta on the d i s t a l inner surface, and four thick plumose setae terminally. 124 Copepodite I I (Fig. 17B) The shape of the animal i s s i m i l a r to that of the C/l stage. The body i s more transparent than the C / l . The length of the animal ranges from 1.1 to 1.4 mm. with an average of 1.3 mm. based on 20 specimens. The cephalothorax i s longer than i t i s i n the C/l stage. There are four free thoracic segments carrying three pairs of well developed swimming and a pair of rudimentary legs. The d i s t a l segment of the urosome i s longer than i t i s i n the C/l stage. The f i r s t antenna (Fig. 18B) consists of eleven segments as i n the C/l stage but the segments are longer than i n the pfevious stage. The outer surface of the segment i s provided with short plumositieis. The most d i s t a l segment carries long setae. The second antenna (Fig. 19B) i s very much simi l a r to the C / l . The coxa consists of two segments, of which the proximal segment i s without setae. The d i s t a l segment of the endopod carries four thick plumose setae and one thin plumose seta on the d i s t a l inner surface and f i v e thick plumose setae terminally. The exopod i s s i m i l a r to that i n the C/l stage. The mandible (Fig. 20B) i s biramous. The endopod i s two segmented. The rest of the details of this appendage i s s i m i l a r to that of the C/l stage. The gnathobase on the f i r s t maxilla (Fig. 21B) consists of nine setae, of which si x setae are stout and are provided with short spines. The rest of the d e t a i l s i s more or less s i m i l a r to that of the C/l stage. The second maxilla (Fig. 22B) i s the smallest appendage and i s sim i l a r to that of the C / l . The maxilliped (Fig. 23B) i s uniramous. The coxa carries four sets of setae. There i s a single long, plumose seta at the lower inner proximal end, the second set consists of two unequal setae, the t h i r d and fourth sets consist of three small plumose setae. The basipod i s as i n 125 the C/l stage. The d i s t a l portion of t h i s appendage consists of three segments. The proximal segment carries two plumose setae at the lower inner surface and one long plumose seta at the d i s t a l inner surface, the second segment carries two plumose setae at the upper inner surface and the th i r d segment carries four plumose setae terminally. Copepodite I I I (Fig. 17C) The length of the animal ranges from 1.6 to 1.9 mm. with an average of 1.7 mm. based upon 20 specimens. The free thoracic segments carry four pairs of well developed swimming legs and one pair of rudimentary legs. The f i r s t antenna (Fig. 18C) consists of twenty segments. I t reaches up to the end of the body. The second antenna (Fig. 19C) i s same as the C/2 stage. The mandible (Fig. 20C) i s the same as the C/2 except for the presence of an additional few setae. The gnathobase of the f i r s t maxilla (Fig. 21C) carries twelve thick spinous setae. The rest of the de t a i l s are the same as that i n the C/2 stage. The second maxilla (Fig. 22C) i s si m i l a r to that of the C/2 stage except that the most lower lobe carries f i v e long, thick plumose setae on the inner surface instead of the four i n the C/2 stage. The coxa of the maxilliped (Fig. 23C) bears three groups of two unequal plumose seta along the inner surface. The basipod bears three shorts plumose setae i n the middle of the segment. The d i s t a l portion of the appendage consists of four segments. The proximal segment carries two plumose setae at the lower inner surface and one at the upper inner surface. The second segment from the proximal end bears one plumose seta at the inner surface, the t h i r d segment bears one on the inner surface and one on the subsurface and the fourth segment with one plumose seta on the subsurface and three terminally. 126 Copepodite IV (Fig. 17D) The length of the animal ranges from 2.6 to 3.1 mm. with an average of 2.8 mm. based on twenty specimens. The cephalothorax i s followed by f i v e free thoracic segments which are broader than they are long. These segments carry the f i v e pairs of swimming legs. The urosome consists of three segments, of which the middle segment i s longer than the f i r s t and the t h i r d segment. The f i r s t antenna (Fig. 18D) i s twenty-four segmented and i t i s longer than the length of the animal. The second antenna (Fig. 19D) i s biramous and i s similar to that of the C/3 stage except that the d i s t a l segment of the endopod carries thirteen plumose setae. The mandible (Fig. 20D) i s si m i l a r to the mandible of the C/3 stage except that i t i s s l i g h t l y larger and the d i s t a l segment of the endopod carries nine plumose setae. The gnathobase of the f i r s t maxilla (Fig. 2lD) bears thirteen strong setae with short spines. The endopod carries three segments and the proximal segment carries three plumose setae, the second segment carries two plumose setae on the inner surface, and the d i s t a l segment carries f i v e plumose setae terminally. The second maxilla (Fig. 22D) i s s i m i l a r to that of the C/3 stage except that there are s i x plumose setae on the most proximal lobe of the C/4. The d i s t a l part of the maxilliped (Fig. 23D) i s divided into f i v e segments. The proximal segment carries four plumose setae, the second carries two plumose setae, the t h i r d carries one, the fourth carries one on the inner surface and one on the outer surface, and the f i f t h segment carries four setae terminally. Copepodite V (Fig. 17E) The C/5 stage i s very s i m i l a r to the adult stage (C/6) except for the absence of genital organs. The length of the animal ranges from 4.5 to 5.1 mm. with an average of 4.7 mm. based on 25 specimens. The urosome consists of four segments, of which the second i s longer than i t i s broad. 127 The f i r s t antenna (Fig. 18E) consists of twenty-four segments and the segments carry aesthetascs. The most d i s t a l segment carries four long setae terminally. The second antenna (Fig. 19E) i s si m i l a r to that of the fourth stage except that the d i s t a l segment of the endopod carries eight setae on the inner surface and seven terminally. The same segment i s l i n e by small plumosities on the outer surface. The mandible (Fig. 20E) has numerous short teeth on the inner surface of the coxa. The second segment of the endopod carries ten plumose setae terminally. The gnathobase of the f i r s t maxilla (Fig. 21E) i s provided with nine thick, plumose setae. The exopod carries ten setae. The rest of the structures are similar to those i n the C/4 stage. The second maxilla (Fig. 22E) i s simi l a r to that of the C/4 stage except that i t carries a single seta i n the middle of the outer surface. The coxa and the basipod of the maxilliped (Fig. 23E) are simi l a r to those i n the C/4 stage. The d i s t a l portion of the appendage consists of five segments, of which the proximal segment carries f i v e plumose setae, the second carries three plumose setae, the t h i r d carries two plumose setae,,and the fourth carries two on the inner surface and one on the outer surface and the f i f t h segment carries fi v e setae terminally. Copepodite VI (Female) (Fig. 17G) The length of the animal ranges from 4.2 mm. to 5.3 mm. with a mean of 4.8 mm. based upon 26 specimen. The gravid females carry numerous colour-less eggs inside the body. The rostrum consists of two short, slender filaments which are 0.35 mm. long each. The f r o n t a l region i s round and the fr o n t a l organ has a small p a p i l l a . The prosome i s four times the length of the urosome and the cephalo-thorax i s l i t t l e less than the length of the prosome. The posterolateral 128 margins of the l a s t free thoracic segment are rounded. The f i r s t segment of the urosome i s the genital segment, which i s a l i t t l e more than half the length of the entire urosome. The raudal rami are twice as long as they are wide and are fringed with small plumo-s i t i e s on the inner surface. Each caudal ramus carries a curved setule on the inner d i s t a l end, a straight plumose setule on the outer d i s t a l corner and four equally long plumose setae terminally. The f i r s t antenna (Fig. 18G) i s twenty-five segmented. The segments one and two, eight and nine are fused. The appendage i s as long as the entire animal. The second antenna (Fig. 19G) i s the same as the C/5. The mandible (Fig. 20G) has v e s t i g i a l teeth on the masticatory region. The d i s t a l segment of the basipod carries one naked setule proximally and three plumose setules d i s t a l l y . The d i s t a l segment of the endopod carries ten plumose setae terminally. The f i r s t maxilla (Fig. 21G) i s degenerated. The gnathobase carries v e s t i g i a l plumosities and the epipod carries seven, long, plumose setae. The endopod i s four segmented, each segment of which carries four plumose setae. The single segmented exopod carries eleven plumose setae. The second maxilla (Fig. 22G) i s same as the C/5 stage. The coxa of the maxilliped (Fig. 23G) bears eight setae along the inner surface, one i s at the proximal most end, two are located one-third from the proximal end, two more are located one-third from the d i s t a l end, and three are at the d i s t a l most end. The endopod i s f i v e segmented. The proximal most segment carries s i x plumose setae, the second segment from the proximal end carries four plumose setae, the t h i r d segment carries three, the fourth carries three d i s t a l l y . o n the inner surface and one proximally on the outer surface and the most d i s t a l segment carries one proximally on the outer surface and three terminally. 129 Copepodite VI (Male) F i g . 17F) The adult male d i f f e r s from that of the female i n a few respects. The length of the animal ranges from 4 mm. to 5.3 mm. with a mean of 4.5 mm. based on 17 specimens. There i s a small ridge on the mid-dorsal surface of the cephalothorax, a t h i r d from the anterior end. The urosome i s five segmented and i s nearly one-third of the prosome in length. Each caudal ramus carries a tiny plumose setule on the inner d i s t a l corner and f i v e plumose setae termally. The f i r s t antenna (Fig. 18F) i s twenty-four segmented, of which the segments one and two, seven and eight are fused. The second antenna (Fig. 19F) i s the same as the adult female. The teeth on the mandible (Fig. 20F) are completely l o s t on the masticatory edge of the coxa. The basipod carries two naked setules d i s t a l l y on the inner surface. The proximal segment of the endopod carries a setule and a plumose seta d i s t a l l y on the inner surface and the d i s t a l segment carries eight, long plumose setae and a setule terminally. The f i r s t maxilla (Fig. 2lF) of the male i s si m i l a r to that of the female, except that the epipod carries two plumose setules and seven long plumose setae on the outer surface. The second maxilla (Fig. 22F) consists of two segments only. The proximal segment of which bears a single setule on the outer surface and four long plumose setae on each of the four lobes on the inner surface.. The d i s t a l segment carries s i x long, plumose setae on the inner surface. The basic structure of the maxilliped (Fig. 23E) i s the same as i n the female. The coxa bears a naked setule proximally on the inner surface, and a plumose setule on the d i s t a l inner surface. The endopod i s f i v e segmented. The proximal two segments are the same as i n the female. The thi r d segment carries two plumose setae on the inner surface, the fourth segment carries two plumose setae on the inner and one plumose seta on the outer surface directed backwards. The most d i s t a l 130 segment c a r r i e s one plumose s e t a on the outer surface d i r e c t e d backwards and three plumose setae t e r m i n a l l y . APPENDIX B Raw Data. APPENDIX B Table 1. Feeding Experiments with the Naupliar Stages of Euchaeta japonica Marukawa Stage Food I n i t i a l Concentration i n Cells Per ml. Mean (Range) Cells Eaten Per Day Per Nauplius Mean (Range) Volume Eaten Per Day Per Nauplius in Cubic Microns Mean (Range) N/2 Dunaliella  t e r t i o l e c t a (heat-killed) 329,150 (205,000-453,300) n i l n i l N/3 N/4 Dunaliella  t e r t i o l e c t a (heat-killed) Dunaliella  t e r t i o l e c t a (heat-killed) 34,442 (25,250-46,388) 27,220 (10,151-50,290) 35,840 (12,110-66,690) 38,710 (15,150-75,250) 10.04 x 10 (83.91 x 10-18.87 x 10 ) 10.84 x 10 6, , (42.42 x 10-21.07 x 10 ) N/5 Dunaliella  t e r t i o l e c t a (heat-killed) 103,700 (35,220-180,700) 31,960 (2,220-68,110) 89.49 x 10 . (616,720-88.89 x 10 ) N/6 Dunaliella  t e r t i o l e c t a (heat-killed) 69,967 (55,750-88,750) 73,660 (50,210-110,000) 20.63 x 10 , r (14.06 x 10-30.88 x 10 ) N/2 Dunaliella t e r t i o l e c t a ( l i v e ) 3,742 (2,927-5,091) n i l n i l N/3 Dunaliella t e r t i o l e c t a ( l i v e ) 4,215 (2,932-5,121) 1,290 (1,300-2,112) 36,120 (5,914-36,400) APPENDIX B Table 1. Stage Continued. Food Feeding Experiments with the Naupliar Stages of Euchaeta japonica Marukawa I n i t i a l Concentration in Cells Per ml. Mean (Range) Cells Eaten Per Day Per Nauplius Mean (Range) Volume Eaten Per Day Per Nauplius i n Cubic Microns Mean (Range) N/4 N/5 N/6 Dunaliella t e r t i o l e c t a ( l i v e ) Ditylum  b r i g h t w e l l i i Ditylum  b r i g h t w e l l i i 3,508 (2,012-5,127) 1,968 (1,647-2,289) 748.0 (25.0-1,247) 4,372 (2,240-5,020) 10,030 (6,272-14,056) 651.5 (235.0-1,068) 44.95 x 10" , (16.22 x 10-73.69 x 10 ) 9,410 (8,770-10,100) 64.93 x 10 (69.34 x 10-60.52 x 10 ) APPENDIX B Table 2. Continued. Feeding Experiments with the Naupliar Stages of Calanus plumchrus Marukawa Stage Food I n i t i a l Concentration Cells Eaten Per Volume Eaten Per in Cells Per ml. Day Per Nauplius Day Per Nauplius Mean (Range) Mean (Range) i n Cubic Microns Mean (Range) N/3 N/4 N/5 N/6 N/4 Dunaliella t e r t i o l e c t a ( l i v e ) Dunaliella t e r t i o l e c t a ( l i v e ) Dunaliella t e r t i o l e c t a ( l i v e ) Dunaliella t e r t i o l e c t a (live) Chaetoceros  serpentrionalis 3,869 (2,717-5,020) 9,606 (3,526-17,760) 5,479 (2,458-9,059) 3,256 (2,787-3,505) 32,029 (12,267-51,792) 1,608 (1,191-2,017) 44.91 x 10^ (33.34 x 10-56.48 x 10 ) 2,232 (541-3,554) 624,960 , (141,480-100.0 x 10 ) 3,365 (1,343-5,556) 94.21 x 10 s (37.60 x 10-15.56 x 10 ) 2,066 (1,460-2,560) 57.66 x 10^ , (41.0 x 10-72.0 x 10 ) 53.0 (21.0-85.0) 16,112 (6,384-25,840) APPENDIX B Table 2. Feeding Experiments with the Naupliar Stages of Calanus plumchrus Marukawa Stage Food I n i t i a l Concentration i n Cells Per ml. Mean (Range) Cells Eaten Per Day Per Nauplius Mean (Range) Volume Eaten Per Day Per Nauplius i n Cubic Microns Mean (Range) N/1 Isochrysis  galbana (l i v e ) 31,467 (10,647-52,287) n i l n i l N/1 Dunaliella  t e r t i o l e c t a (heat-killed) 96,218 (91,729-10.04 x 10 ) n i l n i l N/2 N/3 Dunaliella  t e r t i o l e c t a (heat-killed) Dunaliella  t e r t i o l e c t a (heat-killed) 10.18 x 10 , (99,663-10.299 x 10 ) 86,160 , (10,587-18.09 x 10^) 19,940 (14,980-23,080) 52,370 (2,430-96,160) 55.83 x 10 J (14.96 x 10-64.64 x 10 ) 14.66 x 10 6 ,. (680,000-26.9 x 10 ) N/4 Dunaliella  t e r t i o l e c t a (heat-killed) 94,165 , (31,072-18.7 x 10 ) 17.84 x 10 (72,760-23.9 x 10 ) 49.95 x 10 , (62.47 x 10-67.0 x 10 ) N/5 Dunaliella  t e r t i o l e c t a (heat-killed) 76,144 , (11,407-14.09 x 10 4) 81,010 (67,850-94,180) 32.68 x 10° , (19.01 x 10-26.37 x 10 ) N/6 Dunaliella  t e r t i o l e c t a (heat-killed) 19,717 (15,572-23,861) 69,470 (62,280-76,660) 19.45 x 10" , (17.44 x 10-21.47 x 10 ) APPENDIX B Table 3. Grazing Experiments of the Copepodite Stages of E. japonica it age Food I n i t i a l Concentration i n Cells Per ml. Mean (Range) Cells Eaten Per Day Per Copepodite Mean (Range) Volume Eaten Per Day Per Copepodite i n Cubic Microns Mean (Range) C/l Dunaliella 9,756 34,560 96.56 x 10 5 t e r t i o l e c t a ' (8,591-10,920) (34,'240-34,880) ' (95.84 x 10-97.68 x 10 ) C/l Phaeodac tylum 8,355 22.56 x 10* , 38.12 x 10 6 , tricornutum (7,602-9,109) (21.06 x 10-24.06 x 10 ) (35.57 x 10-40.66 x 10 ) C/l Ditylum 1,588 1,324 91.56 x 10 6 f i , b r i g h t w e l l i i .(1,532-1,638) (1,408-1,244) (85.84 x 10-97.16 x 10 ) C/l Coscinodiscus 425 n i l n i l concinnus (330-525) C/2 Coscinodiscus 498.5 1,960 14.11 x 10 7 ? concinnus (425-572) (1,880-2,040) (14.54 x 10-14.68 x 10 ) C/2 Ditylum 344.5 2,580 35.01 x 10 7, b r i g h t w e l l i i (266-423) (960-4,120) (66.24 x 10-28.4 x 10 ) C/3 Ditylum 1,383 4,050 27.98 x 10 7 ? b r i g h t w e l l i i (1,140-1,626) (3,666-4,440) (25.32 x 10-30.64 x 10 ) C/4 Ditylum 1,531 7,860 54.20 x 10 7 b r i g h t w e l l i i (1,078-1,983) (6,680-9,040) (4,608-6,236) C/4 Dunaliella 11,316 40,660 11.59 x 10 6 , t e r t i o l e c t a (11,502-12,130) (38,840-42,480) (10.88 x 10-11.89 x 10 ) C/5 Ditylum 1,299 1,480 10.13 x 10 7 b r i g h t w e l l i i (980-1,617) (840-2,120) (58 x 106-14.63 x 10 7) APPENDIX B Table 3. Continued. Grazing Experiments of the Copepodite Stages of E. japonica Stage Food I n i t i a l Concentration Cells Eaten Per Volume Eaten Per in Cells Per ml. Day Per Copepodite Day Per Copepodite Mean (Range) Mean (Range) i n Cubic Microns Mean (Range) C/6 female Ditylum  b r i g h t w e l l i i 1,557 (1,540-1,574) 1,300 (1,200-1,400) 89.80 x 10 , (82.80 x 10-96.80 x 10 ) C/6 male Dunaliella  t e r t i o l e c t a Ditylum  b r i g h t w e l l i i 40,610 (25,861-55,360) 2,418 82.62 x 10 . (35.76 x 10-12.94 x 10 ) 34,400 23.13 x 10 7 (10.01 x 10-36.24 x 10 ) 24.77 x 10 8 APPENDIX B Table 4. Grazing Experiments of the Copepodite Stages of C. plumchrus Stage Food I n i t i a l Concentration Cells Eaten Per Volume Eaten Per i n Cells Per ml. Day Per Copepodite Day Per Copepodite Mean (Range) Mean (Range) Mean (Range) C/l (laboratory) Dunaliella t e r t i o l e c t a 4,712 . (1,644-8,066) . C/l (laboratory) Chaetoceros serpentrionalis 32,247 (31,507-32,993) C/l (laboratory) Thalassiosira rotula 2,972 C/l ( f i e l d ) Dunaliella t e r t i o l e c t a 4,329 (4,045-4,612) C/2 Dunaliella t e r t i o l e c t a 3,289 (2,448-4,129) C/3 Dunaliella . t e r t i o l e c t a 2,711 (2,425-3,235) C/3 Ditylum b r i g h t w e l l i i 369 (345-392) C/3 Chaetoceros serpentrionalis 31,207 (30,361-32,053) C/4 Dunaliella t e r t i o l e c t a 3,765 (3,238-4,293) C/4 Ditylum b r i g h t w e l l i i 299 (182-517) 5,184 (1,320-8,112) 14.51 x 10 5, (38.08 x 10 -22.71 X io 5) 45,000 (6,740-83,400) 13.695 x 10^ (20.50 x 10 • -25.34 X 10 5) 13,906 11.82 x 10 7 7,018 (51.04 x 10-89.32 x 10 4) 19.65 x 10 5 (14.29 x 10 • -25.01 X 10 5) 12,106 (9,866-14,348) 33.9 x 10 5 (27.02 x 10 • -40.17 X 10 5) 35,800 (29,200-50,600) 10.01 x 10 6 (81.97 x 10 -14.17 X i o 6 ) 2,600 (2,000-3,142) 17.96 x 10 7 (14.21 x 10 • -21.68 X io 7) 22.76 x 10 4 (20.68 x 10-24.86 x 10 4) 69.22 x 10 6, (62.84 x 10 • -75.58 X 10 6) 20.60 x 10 4 (13.84 x 104-27.36 x 10 4) 57.64 x 10 4 (38.72 x 106--76.55 X 10 6) 5,488 , (4,340-10.16 x 10 ) 37.86 x 10 7 (32.99 x 10: -29.47 X 10 8) APPENDIX B Table 4. Continued. Grazing Experiments of the Copepodite Stages of C. plumchrus Stage Food I n i t i a l Concentration Cells Eaten Per - Volume Eaten Per in Cells Per ml. Day Per Copepodite Day Per Copepodite Mean (Range) Mean (Range) Mean (Range) C/4 Thalassiosira rotula 1,659 (2,049-1,269) 12,816 (13,834-11,838) 10.91 x 10 (11.76 x 10 -10.06 X 10 7) C/5 Dunaliella t e r t i o l e c t a 11,388 (1,850-18,741) 15.59 x 10 4 (27,000-31.81 x 10 5) 43.68 x 10 4 (75.81 x 10 -89.24 X 10 6) C/5 Isochrysis galbana 5,955 (5,682-6,227) 62,400 (47,700-82,800) 48.01 x 10 5 (37.21 x 10 • -64.82 X 10 5) C/5 Phaeodactylum tricornutum 7,184 (2,497-11,871) 56,242 (30,300-82,185) 12.48 x 10 6, (11.15 x 10 • -13.81 X 10 6) C/3 Coscinodiscus concinnus 109 (64.85-165) 2,064 (1,060-2,736) 18.97 x 10 7 (14.86 x 107' -26.27 X 108) C/5 Ditylum b r i g h t w e l l i i 359 (292-435) 2,070 (1,060-3,080) 14.27 x 10 7 (72.90 x 10 • -21.25 X 10 7) C/5 Skeletonema costatum 12,225 (10,417-14,034) 41,800 (24,200-59,600) 31.82 x 10 6, (18.37 x 10 • -45.26 X 10 6) C/5 Chaetoceros serpentrionalis 14,732 (7,182-25,259) 29.88 x 10 4 (14.78 x 10-44. ,98 x 10 4) 90.82 x 10 6 (44.94 x 10 • -13.67 X 10 7) C/6 female Dunaliella t e r t i o l e c t a 8,374 (3,716-13,032) 4,332 (1,308-7,360) 12.14 x 10 5, (36.64 x 10 • -20.61 X 10 5) C/6 female Ditylum b r i g h t w e l l i i 426.6 (253.5-550.18) 788.80 . (46.4-1,700) 54.44 x 10 5. (32.12 x 10 • -11.73 X 10 7) APPENDIX B Table 4. Continued. Grazing Experiments of the Copepodite Stages of C. plumchrus Stage Food I n i t i a l Concentration Cells Eaten Per Volume Eaten Per in Cells Per ml. Day Per Copepodite Day Per Copepodite Mean (Range) Mean (Range) Mean (Range) C/6 Coscinodiscus 164.5 n i l n i l female concinnus (59-270) C/6 female Chaetoceros 77,928 serpentrionalis (68,651-87,237) n i l n i l APPENDIX B Table 5. Predation Experiments o f the Developmental Stages of E. japonica on the F i r s t Day Artemia Na u p l i i Developmental Food Concentration Number cf N a u p l i i Daily Consumption Stage (per ml.) Eaten Per Predator i n /ug.(dry weight) Per Day (±t .05) (±t .05) N/6 1.0 - 3.0 n i l n i l C/l 0.1 - 0.50 5.06 ( 1.90) 25.92 ( 8.80) C/2 0.1 - 0.30 7.740 ( 4.70) 38.70 (23.40) C/3 0.2 - 0.50 23.15 ( 9.0 ) 111.07 (40.3 ) C/4 0.1 - 0.50 19.0 ( 3.0 ) 91.57 (15.89) C/5 0.2 - 0.50 22.17 (21.1 ) 110.85 (34.0 ) C/6—female 0.1 -0.60 7.49 ( 3.89) 37.47 (19.52) C/6—male 0.2 - 0.50 1.35 ( 1-75) 6.60 ( 3.23) APPENDIX B Table 6. Predation Experiments of the Copepodite Stages of E. japonica on the F i f t h Day Artemia Nauplii Developmental Food Concentration Number of Nau p l i i Daily Consumption Stage (Per ml.) Eaten Per Predator i n /ug. (dry weight) Per Day ( t t .05) (It .05) C/l 0.1 - 0.5 3.06 (3.6 ) 11.49 (14.50) C/2 0.1 - 0.5 5.98 (3.3 ) 11.96 ( 6.85) C/3 0.1 - 0.5 15.54 (9.0 ) 31.08 (18.0 ) C/4 0.1 - 0.5 17.74 (7.7 ) 35.15 (15.55) C/5 0.1 - 0.3 6.93 (5.89) 13.88 (11.79) C/6—female 0.2 - 1.0 10.30 (7.20) 23.99 (21.40) C/6—male 2.5 (3 sets) n i l n i l APPENDIX B Table 7. Predation Experiments of the Copepodite Stages of E. japonica on the Second Day Artemia Na u p l i i Developmental Food Concentration Number of Nau p l i i Daily Consumption Stage (Per ml.) Eaten Per Predator i n ,ug.(dry weight) Per Day ( i t .05) ' (±t .05) C/4 0.1 - 0.5 20.01 (16.9 ) 60.04 (50.90) C/5- • . •• 0.1 - 0.3 . • • • 5.87 ( 4.28) 17.11 (12.88) C/6—female 0.1 - 0.5 6.41 ( 3.76) 19.24 (11.30) APPENDIX B Table 8. Predation Experiments of the Copepodite Stages of E. japonica on Tigriopus c a l i f o r n i c u s Developmental Stage C/4 C/5 C/6—female C/6—male Food Concentration (Per ml.) 1.0 - 2.0 2.0 - 5.0 2.0 - 5.0 0.2 and 0.3 Number of Nauplii Eaten Per Predator Per Day (±t .05) 0.51 (0.12) 0.404 (0.11) 1.475 (0.29) n i l Daily Consumption i n mg. (dry weight) (±t .05) 6.65 (5.3 ) 5.218 (2.2 ) 17.7 (3.756) n i l Table 9. Developmental Stage APPENDIX B Pre d a t i o n Experiments of the Copepodite Stages of E. j a p o n i c a on Various Zooplankton Food Type Food Concentra-t i o n (per ml.) Number of Prey Organisms Eaten Per Predator Per Day D a i l y Consumption i n yUg.(dry weight) C / l C / l C / l C / l C/3 C/5 C/5 C/6—female C/6—female C/6—female C/6—-male N a u p l i i of Calanus plumchrus Barnacle nauplius Oncaea b o r e a l i s S c o l e c e t h r i c e l l a S c o l e c e t h r i c e l l a S c o l e c e t h r i c e l l a Ostracods S c o l e c e t h r i c e l l a Gaidius Columbia Park Ostracod Gaidius Columbia Park 2.5 2.5 0.7 .0 1.5 1.0 1.0 1.0 1.0 1.0 1.5 3.0 5.0 1.5 - 3.0 1.0 - 3.0 1.5 3.0 0.051, (0.04 - 0.06) n i l n i l n i i n i l 0.729 (0.936 - 0.5222) b i t s and p i e c e s 0.771 (0.343 - 1.199) b i t s and p i e c e s b i t s and p i e c e s n i l 0.051 (0.04 - 0.06) n i l n i l n i l n i l 21.87 (28.080 - 15.666) 22.130 (10.290 - 35.970) n i l APPENDIX B Table 10. Developmental Stage and Sex of the Predator Predation Experiments of the Male and Female Copepodite Stages V and VI of  E. japonica on F i r s t Day Artemia Nauplii Food Concentra-tion (per ml.) Number of Nauplii Eaten per Copepodite Per Day (±t .05) Daily Consumption i n ,ug. (dry weight) ' (*t .05) C/5 C/5 C/6 C/6 female male female male 0.2 - 0.7 0.15 - 0.7 0.10 - 0.6 0.2 - 0.5 12.53 (5.68) 9.82 (5.42) 7.49 (3.89) 1.35 (1.2 ) 36.58 (14.96) 49.14 (27.24) 37.46 (19.52) 6.75 ( 6.0 ) APPENDIX B Table 11. Predation Experiments of the Developmental Stages of C. plumchrus on F i r s t Day Artemia Na u p l i i Developmental Food Concentra- Number of Nauplii Daily Consumption Stage tion (per ml.) Eaten Per Copepodite i n .ug. (dry weight) Per Day (±t .05) ' N/6 1.0 - 3.0 n i l n i l C/l 0.30 n i l n i l C/2 0.30 n i l n i l C/3 0.30 0.5 (0.33) 2.5 C/4 0.1 - 0.4 5.02 (3.1) 25.0 C/5 0.1 - 0.50 9.91 (5.6) 49.55 C/6—female 0.30 2.0 (1.0) 10.0 APPENDIX B Table 12. Selective Feeding Experiments of the Sixth Nauplius of E. japonica S e r i a l Number Food Species and Concentration (per ml.) Number of Organisms Eaten Per Nauplius Per Day (±t .05) Daily Consumption i n /ug. (dry weight) Per Nauplius Dunaliella t e r t i o l e c t a 5,791.71 292.7 (142.1) 0.017 Coscinodiscus concinnus 1.0 N i l N i l Dunaliella t e r t i o l e c t a 4,115.21 253.3 (121.2) 0.015 Coscinodiscus concinnus 1.0 N i l N i l Dunaliella t e r t i o l e c t a 3,497.71 201.5 (102.5) 0.012 Fi r s t Day Artemia Nauplii 1.0 N i l N i l Dunaliella t e r t i o l e c t a 7,957.68 379.1 (154.5) 0.021 F i r s t Day Artemia Nauplii 1.0 N i l N i l APPENDIX B Table 13. Selective Feeding Experiments of the F i r s t Copepodite Stage of E. japonica S e r i a l Number Food Species and Concentration (per ml.) Number of Organisms Eaten Per Copepodite Per Day (±t .05) Daily Consumption i n /ug. (dry weight) Per Copepodite Ditylum  b r i g h t w e l l i i F i r s t Day Artemia Nauplii Dunaliella  t e r t i o l e c t a F i r s t Day Artemia Nauplii Dunaliella  t e r t i o l e c t a F i r s t Day Artemia Nauplii Dunaliella  t e r t i o l e c t a Ditylum  b r i g h t w e l l i i F i r s t Day Artemia Nauplii 698.0 0.125 6,136.30 0.125 5,482.0 0.125 5,872.0 924.0 0.125 820.0 (396.0) 0.40 ( 0.24) 13,416.0 (6,080.0) 1.2 ( 0.8 ) 53,964.0 (8,712.0) 2.0 ( 0.8 ) 9,680.0 (4,840 ) 1,040.0 (640.0) 1.6 ( 1.2) 0.560 2.0 0.76 6.0 3.16 10.0 0.56 7.2 8.0 APPENDIX B Table 13. Continued. Selective Feeding Experiments of the F i r s t Copepodite Stage of E. japonica S e r i a l Number Food Species and Concentration (per ml.) Number of Organisms Daily Consumption Eaten Per Copepodite i n /ug. (dry weight) Per Day (-t .05) Per Copepodite Dunaliella  t e r t i o l e c t a Ditylum  b r i g h t w e l l i i F i r s t Day Artemia Nauplii Dunaliella  t e r t i o l e c t a Ditylum  b r i g h t w e l l i i F i r s t Day Artemia Nauplii Nauplius of C. plumchrus F i r s t Day Artemia Nauplii 1,724.3 9,948.4 0.125 10,233.6 1,976.4 0.125 0.25 0.25 39,520.0 (18,600) n i l n i l 16,840.0 ( 6,244.0) 4,712.0 ( 2,160.0) 0.28 ( 0.52) 0.029 ( 0.017) 0.200 ( 0.131) 2.3 n i l n i l 1.0 3.2 1.4 0.029 1.04 APPENDIX B Table 14. Selective Feeding Experiments of the Second Copepodite Stage of E. japonica S e r i a l Number Food Species and Concentration (per ml.) Number of Organisms Eaten Per Copepodite Per Day (±t .05) Daily Consumption i n /ug. (dry weight) Per Copepodite Ditylum  b r i g h t w e l l i i 386.0 2,020.0 (62.0) 1.4 F i r s t Day Artemia Na u p l i i 0.25 3.4 ( 2.2) 17.0 Dunaliella t e r t i o l e c t a 3,202.80 10,014.0 (5,002.0) 0.6 F i r s t Day Artemia Nauplii 0.25 6.4 ( 2.4) 32.0 Dunaliella t e r t i o l e c t a 5,908.0 14,400 (5,506.0) 0.84 F i r s t Day Artemia Nauplii 0.125 4.2 ( 2.4) 21.0 F i r s t Day Artemia Nauplii 0.15 0.536 *(0.479 - 0.594) 2.432 *(2.395 - 2.47) Nauplius of C. plumchrus 0.15 0.306 *(0.202 - 0.410) 0.306 *(0.202 - 0.410) APPENDIX B Table 15. Selective Feeding Experiments of the Third Copepodite Stage of E. japonica S e r i a l Food Species and Concentration Number of Organisms Daily Consumption Number (per ml.) Eaten Per Copepodite i n /ug. (dry weight) Per Day (-t .05) Per Copepodite Ditylum 1,406.0 7,528.0 (4,668.0) 5.2 b r i g h t w e l l i i F i r s t Day 0.125 6.8 (1.6) 34.0 Artemia Nauplii Dunaliella 9,466.0 19,648.0 (7,720.0) 1.2 t e r t i o l e c t a F i r s t Day 0.125 14.0 (2.4) 70.0 Artemia Nauplii APPENDIX B T a b l e 16. S e l e c t i v e F e e d i n g E x p e r i m e n t s o f the F o u r t h C o p e p o d i t e Stage o f E. j a p o n i c a S e r i a l Number Food S p e c i e s and C o n c e n t r a t i o n ( p e r ml.) Number o f Organisms D a i l y Consumption E a t e n P e r C o p e p o d i t e i n /ug. ( d r y w e i g h t ) P e r Day (+ t .05) P e r C o p e p o d i t e D u n a l i e l l a  t e r t i o l e c t a D i t y l u m  b r i g h t w e l l i i F i r s t Day A r t e m i a N a u p l i i D i t y l u m  b r i g h t w e l l i i F i r s t Day A r t e m i a N a u p l i i D i t y l u m  b r i g h t w e l l i i F i r s t Day A r t e m i a N a u p l i i A r t e m i a Eggs F i r s t Day A r t e m i a N a u p l i i 4,562.0 761.0 0.125 909.0 0.125 626.0 0.125 3.0 - 4.0 3.0 - 4.0 N i l 3,080.0 ( 1,384.0) 80.0 ( 4.4) 25,260.0 (10,756.0) 13.2 ( 7.2) 2,516.0 ( 2,096.0) 0.88 ( 0.84) N i l 6.34 *(6.72 - 6.96) N i l 2.0 400.0 17.6 66.0 1.76 4.4 N i l 34.20 *(33.60 - 34.80) * - Range APPENDIX B Table 17. Selective Feeding Experiments of the F i f t h Copepodite Stage of E. -japonica S e r i a l Number Food Species and Concentration (per ml.) Number of Organisms Eaten Per Copepodite Per Day (±t .05) Daily Consumption i n /ug. (dry weight) per Copepodite Ditylum  b r i g h t w e l l i i F i r s t Day Artemia Na u p l i i Ditylum  b r i g h t w e l l i i F i r s t Day Artemia Nauplii Nitzschia Sp. F i r s t Day Artemia Nauplii 605.0 0.125 906.0 0.125 3,603.0 0.125 4,120.0 (3,096) 4.08 ( 0.8) 3,648.0 (1,068.0) 2.8 ( 1.2) 17,136.0 (9,000.0) 5.2- ( 2.8) 2.88 20.4 2.4 14.0 8.4 26.0 APPENDIX B Table 18. Selective Feeding Experiments of the Sixth Copepodite Stage (Female) of E. japonica S e r i a l Food Species and Concentration Number of Organisms Daily Consumption Number (per ml.) Eaten Per Copepodite i n /ug. (dry weight) Per Day (-t .05) Per Copepodite 1 Ditylum 1,548.0 1,548 (1,424) 1.08 br i g h t w e l l i F i r s t Day 0.125 2.32 (0.88) 11.6 Artemia Nauplii 2 Ditylum 147.0 2,988 (1,824) 1.8 b r i g h t w e l l i i F i r s t Day 0.033 1.2 (0.6 ) 6.0 Artemia Nauplii 3 Ditylum 380.0 4,212 (1,206) 2.4 b r i g h t w e l l i i F i r s t Day 0.033 1.32 (0.06) 6.6 Artemia Nauplii 4 Nauplius of 0.20 12.95 12.95 C± plumchrus (10.47 - 15.43) (10.47 and 15.43) Nauplius of 0.05 4.21 42.15 E. japonica ( 4.07 - 4.36) (40.70 and 43.60) Barnacle Nauplii 0.20 N i l N i l APPENDIX B Table 18. Continued. Selective Feeding Experiments of the Sixth Copepodite Stage (Female) of Se r i a l Number E. japonica Food Species and Concentration (per ml.) Number of Organisms Eaten Per Copepodite Per Day (±t .05) Daily Consumption i n ,ug. (dry weight) Per Copepodite Artemia Eggs Fi r s t Day Artemia Nauplii Dead-second Day Artemia Nauplii Live-second Day Artemia Nauplii 3.0 and 4.0 3.0 and 4.0 0.15 and 0.30 0.15 and 0.30 N i l 2.04 (1.92 and 2.16) 2.33 (0.49 and 4.18) 4.32 (0.97 and 7.67) N i l 10.20 (9.60 and 10.80) 6.99 (1.47 and 12.54) 14.96 (2.91 and 23.01) Table 19. S e r i a l Number APPENDIX B Selective Feeding Experiments of the Sixth Copepodite Stage (Male) of E. japonica Food Species and Concentration (per ml.) Number of Organisms Eaten Per Copepodite Per Day ( t t .05) Daily Consumption i n /ug. (dry weight) Per Copepodite Ditylum 2,481 b r i g h t w e l l i i F i r s t Day 0.125 Artemia Nauplii Thalassiosira 6,944 rotula F i r s t Day 0.125 Artemia Nauplii 34,400 (15,624) N i l 13,440 (5,500) N i l 24.08 N i l 5.37 N i l APPENDIX B Table 20. Selective Feeding Experiments of the Copepodite Stages of E. japonica Developmental Stage Food Species Food Concentration (per ml.) Daily Consumption i n /ug. (dry weight) Per Copepodite (±t .05) C/l C/2 C/3 C/4 F i r s t Day Artemia Nauplii F i f t h Day Artemia Nauplii F i r s t Day Artemia Nauplii F i f t h Day Artemia Nauplii F i r s t Day Artemia Nauplii F i f t h Day Artemia Nauplii F i r s t Day Artemia Nauplii F i f t h Day Artemia Nauplii 0.2 - 0.3 0.2 - 0.3 0.2 - 0.3 0.2 - 0.3 0.2 - 0.3 0.2 - 0.3 0.15- 0.3 0.15- 0.3 14.57 (11.4 ) 3.64 ( 2.6 ) 26.05 (10.8 ) 11.55 ( 4.94) 51.95 (36.81) 15.31 ( 6.62) 87.35 (52.97) 32.72 (15.34) APPENDIX B Table 20. Continued. Selective Feeding Experiments of the Copepodite Stages of E. japonica Developmental Stage Food Species Food Concentration (per ml.) Daily Consumption i n /ug. (dry weight) per Copepodite (-t .05) C/5 C/6 female F i r s t Day Artemia Nauplii F i f t h Day Artemia Nauplii F i r s t Day Artemia Nauplii F i f t h Day Artemia Nauplii 0.2 - 0.3 0.2 - 0.3 0.1 - 0.3 0.1 - 0.3 36.45 (12.69) 10.55 ( 4.34) 58.73 ( 4.14) 19.31 (19.67) APPENDIX B Table 21 The results of the analysis of variance of four variables of concentration of the prey (C) , size of the prey (S) , developmental stage of the predator (D), and the number of replications (R) . Source of Degrees of Sums of Square Mean Square F-Ratio Variables Freedom c 4 0.44106D 03 0.11026D 03 16.03* S 1 0.12826D 02 0.12826D 02 1.86 CS 4 0.13314D 01 0.33286D 00 0.05 D 4 0.20883D 03 0.52207D 02 7.59* CD 16 0.63154D 03 0.39471D 02 5.74* SD 4 0.19160D 02 0.47900D 01 0.70 CSD 16 0.83897D 02 0.52436D 01 0.76 R 6 0.3268OD 02 . 0.54467D 01 0.79 CR 24 0.92063D 02 0.38360D 01 0.56 SR 6 0.19274D 02 0.32124D 01 0.47 CSR 24 0.65469D 02 0.27279D 01 0.40 DR 24 0.20069D 03 0.83621D 01 1.22 CDR 96 0.65614D 03 0.68348D 01 0.99 * s i g n i f i c a n t difference APPENDIX B Table 21. Continued. The results of the analysis of variance of four variables of concentration of the prey (C) , size of the prey (S), developmental stage of the predator (D) , and the number of repl i c a t i o n s (R). Source of Degrees of ' Sums of Square Mean Square F-Ratio Variables Freedom SDR 24 0.15804D 03 0.65850D 01 0.96 ERROR 96 0.66050D 03 0.68802D 01 TOTAL 349 0.32835D 04 APPENDIX B Table 22. Selective Feeding Experiments of the Sixth Nauplius of C. plumchrus S e r i a l Food Species and Concentration Number (per ml.) Number of Organisms Eaten Per Nauplius Per Day ( t t .05) Daily Consumption i n /ug. (dry weight) Per Nauplius Dunaliella t e r t i o l e c t a 2,521.0 207.5 (112.1) 0.012 Coscinodiscus concinnus 1.0 N i l N i l Dunaliella t e r t i o l e c t a 5,271.22 452.1 (172.1) 0.027 Coscinodiscus concinnus 1.0 N i l N i l Dunaliella t e r t i o l e c t a 4,171.63 361.2 (150.0) 0.021 Fi r s t Day Artemia Nauplii 1.0 N i l N i l Dunaliella t e r t i o l e c t a 5,717.81 392.7 (121.5) .023 Fi r s t Day Artemia Nauplii 1.0 N i l N i l APPENDIX B Table 23. Selective Feeding Experiments of the F i r s t Copepodite Stage of C. plumchrus S e r i a l Food Species and Concentration Number (per ml.) Number of Organisms Eaten Per Copepodite Per Day (±t .05) Daily Consumption i n /ug. (dry weight) Per Copepodite Dunaliella t e r t i o l e c t a 10,225 25,456 (23,424) 1.2 Ditylum  b r i g h t w e l l i i Dunaliella t e r t i o l e c t a 963 6,977 892 ( 696) 9,582 ( 4,420) 0.6 0.4 F i r s t Day Artemia Nauplii 0.125 N i l N i l APPENDIX B Table 24. Selective Feeding Experiments of the Second Copepodite Stage of C. plumchrus S e r i a l Number Food Species and Concentration (per ml.) Number of Organisms Eaten Per Copepodite Per Day ( t t .05) Daily Consumption in /ug. (dry weight) Per Copepodite Dunaliella t e r t i o l e c t a 2,788 1,684 (820) 0.08 Ditylum  b r i g h t w e l l i i 368 1,800 (618) 1.2 Dunaliella t e r t i o l e c t a 3,857 N i l N i l Ditylum  b r i g h t w e l l i i 184 918 (402 0.6 APPENDIX B Table 25. Selective Feeding Experiments of the Third Copepodite Stage of C. plumchrus S e r i a l Food Species and Concentration Number (per ml.) Number of Organisms Daily Consumption Eaten Per Copepodite i n ,ug. (dry weight) Per Day ( t t .05) Per Copepodite Dunaliella  t e r t i o l e c t a Ditylum  b r i g h t w e l l i i Dunaliella  t e r t i o l e c t a Ditylum  b r i g h t w e l l i i Dunaliella  t e r t i o l e c t a F i r s t Day Artemia Nauplius Dunaliella  t e r t i o l e c t a F i r s t Day Artemia Nauplius 4,309.75 204.25 7,006.75 203.12 2,992.34 0.125 3,178 0.125 9,210 (8,088) 836 ( 444) 14,898 (9,700) 463 ( 244) 19,200 (4,934) 7.4 ( 2) 23,282 1.6 ( 0.9) 0.4 0.40 0.8 0.32 1.2 37.0 1.4 8.4 APPENDIX B Table 26. Selective Feeding Experiments of the Fourth Copepodite Stage of C. plumchrus S e r i a l Food Species and Concentration Number (per ml.) Number of Organisms Daily Consumption Eaten Per Copepodite i n ^ ug.(dry weight) Per Day (±t .05) Per Copepodite Coscinodiscus concinnus F i r s t Day Artemia N a u p l i i Coscinodiscus concinnus F i r s t Day Artemia Nauplii Dunaliella  t e r t i o l e c t a Ditylum  b r i g h t w e l l i i Dunaliella  t e r t i o l e c t a Ditylum  b r i g h t w e l l i i 29.2 0.05 146.50 0.125 5,612.70 213.8 5,965.5 486.5 1,364 ( 126) N i l 1,040 ( 254) N i l 24,097 (6,412) 1,460 ( 504) 17,808 (5,020) 3,612 (1,606) 1092 N i l 832 N i l 1.4 1.7 1.0 2.6 APPENDIX B Table 27. Selective Feeding Experiments of the F i f t h Copepodite Stage of C. plumchrus S e r i a l Food Species and Concentration Number (per ml.) Number of Organisms Daily Consumption Eaten Per Copepodite i n ,ug. (dry weight) Per Day (±t.05) Per Copepodite Dunaliella  t e r t i o l e c t a Ditylum  b r i g h t w e l l i i Dunaliella  t e r t i o l e c t a Ditylum  b r i g h t w e l l i i Dunaliella  t e r t i o l e c t a F i r s t Day Artemia Nauplii Dunaliella  t e r t i o l e c t a F i r s t Day Artemia Nauplii 16,579.50 537.25 2,503.25 199.67 3,106.25 0.125 4,021.75 0.125 133,796 (46,000) 6,812 ( 2,880) 19,428 ( 6,720) 2,554 ( 1,282) 18,792 (17,606) 2.4 (0.4) 18,360 ( 8,480) 5.2 (3.6) 4.0 4.77 1.2 1.79 1.2 12.0 1.2 26.0 APPENDIX B Table 28. Selective Feeding Experiments of the Sixth Copepodite Stage of C. plumchrus S e r i a l Food Species and Concentration Number of Organisms Daily Consumption Number (per ml.) Eaten Per Copepodite i n /ug. (dry weight) Per Day ( t t .05) Per Copepodite 1 Dunaliella 3,334.12 10,468 (5,400) 0.52 t e r t i o l e c t a F i r s t Day Artemia Nauplii 0.125 N i l N i l APPENDIX B Table 29. Results obtained when a mixture of various-sized Dunaliella t e r t i o l e c t a was offered to the copepodite stages of C_^  plumchrus. Data are presented as per cent eaten of the available volume of food Volume i n cubic microns Control replicates Experimental replicates 50.22 100.44 200.88 401.76 803.52 1607.04 Developmental Stage Serial Number Food Concentration i n Cubic Microns Per ml, C/l C/2 C/3 C/4 C/5 1 2 1 2 1 2 1 2 44636.34 10758.04 14440.51 44.83 3946.56 45.05 26130.74 0 49624.26 15870.07 21130.75 1027.22 30696.16 7190.58 38143.45 68812.29 440652.68 288429.93 210079.46 102267.29 330501.50 101555.39 326378.06 1354858.0 1858153.25 859010.62 875777.12 569117.00 437219.62 580956.62 423267.81 1192288.50 487471.93 147357.31 331980.62 201694.40 63483.73 211832.06 54194.82 98497.67 21914.17 5706.81 19429.73 4793.72 10338.25 5057.11 4282.69 13848.53 APPENDIX B Table 29. Continued. Results obtained when a mixture of various-sized Dunaliella t e r t i o l e c t a was offered to the copepodite stages of C^ plumchrus. Data are presented as per cent eaten of the available volume of food Developmental S e r i a l Percentage of Available Food Eaten Stage Number C/l 1 1.32 1.12 0.6 0.86 0.77 0 2 0 0.87 1.78 0.16 0 1.99 C/2 1 3.37 0 1.37 1.05 1.01 0 2 29.80 0 4.99 3.59 0.46 C/3 1 11.14 6.46 4.97 4.87 5.59 4.71 2 25.53 25.53 7.86 7.05 6.27 0 C/4 1 6.42 0 3.02 3.44 6.19 0 C/5 2 0 1.65 1.37 0 - 18.2 APPENDIX B Table 30. Results obtained when a mixture of various-sized Chaetopterus chains was offered to the copepodite stages of plumchrus. Data are presented as per cent eaten of the available volume of food Volume i n cubic microns Control replicates Experimental replicates Developmental S e r i a l Stage Number 43.20 2 4 86.40 2 4 172.80 2 4 345.60 2 4 691.20 2 4 1382.40 2 4 Food Concentration i n Cubic Microns per ml. 2764.80 2 4 C/l C/3 C/5 C/6 female 1 342990.68 2 0.00 1 57180.02 2 69563.15 3108127.50 4196385.01 1594233.75 253197.28 54733.00 4544253.00 3864339.00 855951.87 268917.93 2637641.50 4737223.01 1384581.75 261523.46 2753386.00 4939237.01 1530829.75 82805.93 0.0 81270.48 36251.74 127906.84 161386.62 1 62358.24 423508.06 2744654.50 3163337.00 1058504.50 184762.34 42436.46 2 19701.51 110047.28 754523.00 877775.37 337434.12 64863.88 19637.92 1 297571.56 737402.62 4754491.01 11707574.02 7396055.01 2 302337.75 699133.87 4062780.50 9205002.02 5396722.01 1399673.75 223629.68 887107.12 314668.81 APPENDIX B Table 30. Continued. Results obtained when a mixture of various-sized Chaetopterus chains was offered to the copepodite stages of C^ plumchrus. Data are presented as per cent eaten of the available volume of food Developmental Stage S e r i a l Number Percentage of Available Food Eaten C/l 0 0 3.0 0 0.25 0.23 0.03 0 0.0 0.034 0 3.499 2.399 C/3 1 2 0 0 2.94 0 8.0 2.99 3.74 7.05 0.58 0 0.0 0 0.0 0 C/5 1 2 4.23 0 8.38 19.39 8.45 23.29 9.1 24.1 9.56 13.07 10.52 24.44 9.51 17.28 C/6 female 1 2 0.53 0.43 0.91 0.51 0.57 0.0 0 0 0 0.18 0 0 0 1.76 APPENDIX B Table 31. Results obtained when a mixture of various-sized Ditylum b r i g h t w e l l i i was offered to the copepodite stages of C. plumchrus. Data are present as per cent eaten of the available volume of food Volume i n 4546.21 cubic microns Control replicates 2 Experimental 4 replicates 9092.42 2 4 18184.84 2 4 36369.68 2 4 72739.36 2 4 145478.72 2 4 Developmental Stage S e r i a l Number Food Concentration i n Cubic Microns per ml. C/3 1 449108.25 1961154.75 6294328.01 2858846.0 208051.93 82261.15 2 436080.68 2573161.50 8243702.01 3363187.0 297584.62 365093.75 C/4 1 545060.25 2 1019991.62 3095933.50 7197097.01 2521898.0 484102.87 0 773020.37 1996406.50 6831051.01 8199695.01 2468746.50 C/5 C/6 female 1 821927.62 2 1019991.62 1 4485837.01 4265935.01 10810820.02 773020.37 1996406.50 3886381.50 11663400.02 3756617.50 340253.06 146577.90 6831051.01 8199695.01 2468746.50 32515756.04 25000732.05 2075746.0 APPENDIX B Table 31. Continued. Results obtained when a mixture of various-sized Ditylum b r i g h t w e l l i i was offered to the copepodite stages of C^ plumchrus. Data are present as per cent eaten of the available . volume of food Developmental S e r i a l Percentage of Available Food Eaten Stage Number C/3 1 4.07 2.92 3.7 5.02 2.02 0 2 2.30 2.59 3.76 4.80 3.43 4.58 C/4 1 2.38 5.47 5.98 6.51 7.16 2 0 0.58 0.64 0.71 0.52 0.71 C/5 1 0.24 2.77 4.56 7.36 5.5. 0 2 0 0.06 6.35 7.15 5.17 7.13 C/6 1 1.61 1.34 0,59 1.51 1.09 0.32 female APPENDIX B Table 32. Predation Experimental Results of the Second and Sixth (Female) Copepodite Stages of E. japonica i n the Summer and F a l l Developmental Stage Food Species Season Average Food Concentration. No. of Artemia Nauplii per ml. Average weight Consumed i n ,ug. (dry weight) per Copepod Per Day C/2 C/2 C/6—female C/6—female F i r s t Day Artemia Nauplii F i r s t Day Artemia Nauplii F i r s t Day Artemia Nauplii F i r s t Day Artemia Nauplii Summer F a l l Summer F a l l 0.10 to 0.30 0.10 to 0.30 0.10 to 0.60 0.1 to 0.60 23.7 (13.85-39.98) 38.7 (22.95-55.05) 37.46 (16.10-62.30) 28.6 (4.8 -52.0) APPENDIX B Table 33. Grazing Experiments of the Copepodite Five of C. plumchrus i n the Summer Food Species Food Concentration (Cells Per ml.) Number of Ce l l s Eaten Per Copepodite Per Day Mean (Range) Volume Consumed i n Cubic Microns Per Copepodite Per Day Dunaliella t e r t i o l e c t a Phaeodactylum tricornutum Isochrysis galbana Ditylum b r i g h t w e l l i i Coscinodiscus concinnus Skeletonema costatum 10,857 (8,157 - 13,754) 9,895 (7,504 - 12,286) 357 ( 209.34 - 504.0) 241 ( 86.0 - 381.0) 1,155.0 ( 115 - 4,366) 29,789 (19,184 - 40,395) 14,240 ( 0 - 57,040 ) 25,608.75 (15,090 - 36,127.5) n i l ( 0 247.5 742.50) 10,987.5 ( 0.0 - 63,150) n i l 39.87 x 10^ 43.28 x 10 6 n i l 17.08 x 10 6 79.11 x 10 7 n i l Table 34. Food Species APPENDIX B Grazing Experiments of the Copepodite Five of C. plumchrus i n the F a l l Food Concentration (Cells Per ml.) Number of Cell s Eaten Per Copepodite Per Day Mean (Range) Volume Consumed i n Cubic Microns Per Copepodite Per Day Dunaliella t e r t i o l e c t a 7,646 (5,035 - 10,840) 13,384 (5,300 - 29,068) 40.67 x 10 5 S e r i a l Number Table 35, APPENDIX B Selective Feeding Experiments of the Copepodite Five of C. plumchrus i n the Summer Food Species Food Concentration (Cells Per ml.) Number of Organisms Eaten Per Copepodite Per Day (±t .05) Volume Consumed i n Cubic Microns Per Copepodite Per Day Dunaliella t e r t i o l e c t a Coscinodiscus concinnus Ditylum b r i g h t w e l l i i F i r s t Day Artemia Nauplii 13,511 626 1,155 0.125 n i l 2,268 (1,580) n i l n i l n i l 16.28 x 10 7 n i l n i l APPENDIX B Table 36. Seasonal and D a i l y V a r i a t i o n i n Feeding of the Copepodite Stages of E. j a p o n i c a and C. plumchrus Expressed i n Percentage of the Number of Animals Examined. SEASON SPRING SUMMER FALL WINTER Species and Developmental Stage Night Day Night Day Night Day Night Day E. j a p o n i c a C / l MEAN C. plumchrus C / l MEAN E. j a p o n i c a C/2 MEAN C. plumchrus C/2 MEAN E. j a p o n i c a C/3 MEAN N i l N i l (20)* (14) NIL N i l 64 (27) (45) 32 N i l N i l (15) (10) NIL N i l 64 (63) (50) 32 N i l N i l (7) (9) NIL N i l . N i l (15) (12) NIL : N i l N i l (6) (5) NIL N i l N i l (10) (5) NIL N i l 100 (5) (1) 50 ; N i l 100 (5) (2) . 50 N i l N i l (4) (10) NIL 3.9 N i l (51) (37) 1.95 N i l 5.4 , (5) (112) 2.7 * Number of animals — Not a v a i l a b l e examined i s given i n Parenthesis APPENDIX B Table 36. Continued. Seasonal and D a i l y V a r i a t i o n i n Feeding of the Copepodite Stages of E. j a p o n i c a and C. plumchrus Expressed i n Percentage of the Number of Animals Examined. SEASON SPRING SUMMER FALL WINTER Species and Developmental Stage Night Day Night Day Night Day Night Day C. plumchrus C/3 MEAN E. j aponica C/4 MEAN C. plumchrus C/4 MEAN E. j a p o n i c a C 7 5 MEAN C. plumchrus C/5 MEAN 33.5 47.5 (40) (50) 40.5 4 9.5 (60) (50) 78 6.75 76 77.0 9.12 9.5 (500) (500) 9.31 57.5 22 (3000) (3120) 40.0 N i l (75) (70) 2.5 0.75 3.75 (450) (400) 2.25 N i l N i l (2965) (2700) NIL N i l N i l (55) (60) NIL N i l 3.75 (500) (500) 1.88 2.25 1.5 (2841) (2912) 1.8 2.3 (45) 5.1 (42) 9.0 6.0 (500) (500) 7.5 N i l N i l (2975) (3000) NIL — Not a v a i l a b l e APPENDIX B Table 36. Continued. Seasonal and Daily Variation i n Feeding of the Copepodite Stages of E. japonica and C. plumchrus Expressed i n Percentage of the Number of Animals Examined. SEASON SPRING SUMMER FALL WINTER Species and Developmental Stage Night Day Night Day Night Day Night Day E. japonica C/6-female 0.2 0.3 (1050) (1100) N i l 0.3 (1150) (1200) 8 4.5 (1070) (1100) 3.0 9.0 (1000) (1011) MEAN 0.25 0.15 6.25 6.0 E. japonica C/6-male N i l N i l (36) (50) N i l N i l (70) (52) N i l N i l (60) (57) N i l N i l (41) (36) MEAN NIL NIL NIL NIL C. plumchrus C/6-female — • — — N i l N i l (370) (200) MEAN NIL — Not available 179 APPENDIX B Table 37. T o t a l Volume of P a r t i c u l a t e Matter A v a i l a b l e In D i f f e r e n t Seasons at Various Depths i n Howe Sound, B. C. Seasons Depth i n Range of Diameter T o t a l Volume Metres of P a r t i c l e s i n A v a i l a b l e i n Microns Cubic Microns Per ml. Near Surface Water Spring March '68 100 3.57 to 18.0 26.. 75 X 1 0 5 * F a l l 100 3.57 to 18.0 18.99 x 10 5 October '68 Winter 50 3.57 to 18.0 76.55 x 1 0 4 February '69 and 14.3 to 71.9 12.55 X 1 0 6 Near Bottom Water Spring March '68 230 3.57 to 14.3 49.85 X 4 10 * March '69 225 3.57 to 14.3 88.46 X 1 0 4 A p r i l '68 230 3.57 to 14.3^ 35.45 X 1 0 4 May "68 230 3.57 to 18.0 90.40 X 5 10; Mean 26.94 X 1 0 5 Summer June '68 230 3.57 to 14.3 55.58 X 10* August '68 230 3.57 to 14.3 45.35 X i t ) 4 September '68 230 3.57 to 14.3 48.43 X 1 0 * Mean 49.79 X 10* F a l l November '68 230 3.57 to 18.0 87.22 X i o 4 * Data i n F i g - 28 180 APPENDIX B Table 37. Continued. T o t a l Volume of P a r t i c u l a t e Matter A v a i l a b l e i n D i f f e r e n t  Seasons at Various Depths i n Howe Sound, B. C. Seasons Depths i n Range of Diameter T o t a l Volume Metres of P a r t i c l e s i n A v a i l a b l e i n Microns ^ Cubic Microns Per ml. Near Bottom Water Winter December '68 230 3.57 to 18.0 14.3 to 45.3 Zooplankton of 150-200 /u 12.92 20.97 97.47 X X X < * * * February '69 225 3.5 to 18.0 64.31 X i o 4 February '69 225 3.57 to 14.3 71.09 X i o 4 January ' 68 230 3.57 to 14.3 83.23 X 105 Mean 24.43 X 108 * Data i n F i g . 27 APPENDIX C Tables and figures of phytoplankton and zooplankton species used i n the laboratory feeding experiments. 181 APPENDIX C Table 1. Phytoplankton Species Used f o r the Grazing Experiments i n the Laboratory Food Species Average Width i n Micron (Range) Average Volume i n Cubic Microns 1. I s o c h r y s i s galbana 2. D u n a l i e l l a t e r t i o l e c t a 3. Phaeodactylum tricornutum 4. Ditylum b r i g h t w e l l i i 5. Coscinodiscus concinnus 6. Chaetoceros s e r p e n t r i o n a l i s 7. Skeletonema costatum 8. T h a l l a s s i o s i r a r o t u l a 9. N i t z s c h i a species 5 5 (4-6^) 9 (7-9) 4 (3-5) 38 (34-49) 78 (68-91) 4 (3-5) 8 (4.8-9.6) 25 (18-32) 10 (7-12) 78 280 169 69,000 72,000 304 760 8,500 2,000 182 APPENDIX C Table 2. Zooplankton Species Used f o r P r e d a t i o n Experiments i n the Laboratory Food Species Length i n Microns 1. Artemia eggs 200 (diameti 2. Newly hatched Artemia n a u p l i i 375 3. Second day Artemia n a u p l i u s 500 4. F i f t h day Artemia n a u p l i u s 800 5. Copepodite stage one of Euchaeta j a p o n i c a 1,000 6. Copepodite stage one of Calanus plumchrus 900 - 1,300 7. Copepodite stage two of C. plumchrus 1,200 - 1,500 8. Copepodite stage three of C. plumchrus 1,800 - 2,400 9. Copepodite stage four of C. plumchrus 2,800 - 3,400 10. Copepodite stage f i v e of C. plumchrus 4,000 - 5,400 11. Nauplius of E. jap o n i c a 500 700 12. Nauplius of C. plumchrus 250 - 700 13. Gaidius Columbia Park 2,100 14. Tig r i o p u s c a l i f o r n i c u s 900 15. Oncaea b o r e a l i s 700 - 1,400 16. F i s h f r y 1,600 17. F i s h egg 1,300 (diamet« 18. T i n t i n n i d s 80 19. F i r s t day barnacle n a u p l i u s 380 20. Ostracods 1,200 21. S c o l e c e t h r i c e l l a 1,200 - 2,000 Figure 1. D u n a l i e l l a t e r t i o l e c t a Figure 1. Phaeodactylum tricornutum Fl6\. z 184 Figure 3. Ditylum b r i g h t w e l l i i FlCri -3 Figure 4. Chaetoceros s e r p e n t r i o n a l i s Figure 5A. Coscinodiscus concinnus - surface view Figure 5B. Coscinodiscus concinnus - l a t e r a l view Figure 6. T h a l a s s i o s i r a r o t u l a Figure 7. Skeletonema costatum Figure 8. N i t z s c h i a sp. Fl<5i <£ Figure 9. F i r s t day Artemia n a u p l i u s Figure 10. F i f t h day Artemia n a u p l i u s 190 Figure 11. Barnacle n a u p l i u s Figure 12. T i g r i o p u s c a l i f o r n i c u s Figure 13. Oncaea b o r e a l i s R ft • M f\6 ta F161 13 191 Figure 14 and Figure 15. Crustacean remains from the guts of the copepodite stages of Euchaeta j a p o n i c a He, .15" 192 F i g u r e 16. Remains of Coscinodiscus sp. from the guts of the copepodite stages of Calanus plumchrus Figure 17. Remains of Ditylum b r i g h t w e l l i i from the guts of the copepodite stages of C^ plumchrus |-|6i - It Figure 18. I s o c h r y s i s galbana 

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