Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Comparative morphology of sibling species of Metridia (Copepoda:Calanoida), M. lucens, M. pacifica and… Thorp, Arthur Chadwick 1980

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1980_A6_7 T47.pdf [ 4.7MB ]
Metadata
JSON: 831-1.0094801.json
JSON-LD: 831-1.0094801-ld.json
RDF/XML (Pretty): 831-1.0094801-rdf.xml
RDF/JSON: 831-1.0094801-rdf.json
Turtle: 831-1.0094801-turtle.txt
N-Triples: 831-1.0094801-rdf-ntriples.txt
Original Record: 831-1.0094801-source.json
Full Text
831-1.0094801-fulltext.txt
Citation
831-1.0094801.ris

Full Text

COMPARATIVE MORPHOLOGY OF SIBLING SPECIES OF Metridia (CQPEPQDA:CALANQIDA). M. Tucens, M. pacif ica AND A SPECIES INDETERMINATA FROM INDIAN ARM, BRITISH COLUMBIA by ARTHUR CHADWICK THORP B.Sc, Simon Fraser University, 1972 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES Department of Zoology We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA June, 1980 © Arthur Chadwick Thorp, 1980 In presenting th i s thes is in pa r t i a l fu l f i lment of the requirements for an advanced degree at the Un ivers i ty of B r i t i s h Columbia, I agree that the L ibrary shal l make it f ree ly ava i lab le for reference and study. I further agree that permission for extensive copying of th is thesis for scho lar ly purposes may be granted by the Head of my Department or by his representat ives. It is understood that copying or pub l i ca t ion of th is thes is for f inanc ia l gain sha l l not be allowed without my writ ten permission. Depa rtment The Univers i ty of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 - i i -ABSTRACT Metridia lucens and M. pacifica previously have been differentiated primarily by the structure of the male f i f th legs. lucens originally was described to have one large spine on the inner margin of the fourth segment and _M. pacifica to have two spines, one each on the third and fourth joints. Some authors have reported M. lucens with two so-called spines on the same segment and _M. pacif ica also with two such spines but located together on the fourth segment. This led to M. pacif ica being questioned as a species by certain authors who claimed i t synonymous with M. lucens. In the present study, _M. lucens from the Northwestern Atlantic is compared with M. pacifica from the Northeastern Pacific and differences in size and structure are evident to separate them. The f i f th pair of legs on adult males and females were examined and findings indicated errors in the original descriptions of both species. Another Metridia population, found in the coastal waters of Brit ish Columbia, was compared with the described species. It was found to be similar to M. lucens and could be, in part, the reason for the past confusion between the Atlantic and Pacif ic species. - i i i -TABLE OF CONTENTS page ABSTRACT i i TABLE OF CONTENTS i i i LIST OF TABLES iv LIST OF FIGURES v ACKNOWLEDGEMENTS v i i i INTRODUCTION 1 MATERIAL AND METHODS 4 Collection 4 Sorting 5 Dissection and slide preparation 5 Measurements 6 Statist ical analyses 17 I l lustrations 17 Key words 18 RESULTS 20 Synonymy 20 Regression analyses - females 25 Regression analyses - males 36 DISCUSSION 46 SUMMARY 70 LITERATURE CITED 72 - i v-LIST OF TABLES page Table 1. Female body measurement stat i s t ics from analysis 40 of covariance. Intercepts and slopes derived by the regression of measurements against prosome length. Table 2. Male body measurement stat i s t ics from analysis of 41 covariance. Intercepts and slopes derived by the regression of measurements against prosome length. Table 3. Female f i f th leg measurement stat ist ics from 42 analysis of covariance. Intercepts and slopes derived by the regression of measurements against prosome length. Table 4. Male f i f th leg measurement stat ist ics from 43 analysis of covariance on Metridia Tucens and the Metridia specimen from Indian Arm. Intercepts and slopes derived by the regression of measurements against prosome length. Table 5. Tail area probability of t-tests between slopes 44 (b^=b2) for body measurements of female and male Metridia specimens. Table 6. Tail area probability of t-tests between adjusted 45 group means (Yi=Y2) f ° r b o d y measurements of female and male Metridia specimens. -V-LIST OF FIGURES page Figure 1. I l lustrations of Metridia specimen (female) from 8 Indian Arm, Brit ish Columbia. Description of measurements for al l female specimens (uppercase letters.) Figure 2. I l lustrations of the Metridia specimen (male) from 9 Indian Arm, Brit ish Columbia. Description of measurements for al l male specimens (uppercase let ters ) . Features of f i f t h leg (lowercase letters) . Figure 3. I l lustrations of Metridia lucens (female) 10 Figure 4. I l lustrations of Metridia lucens (male) 11 Figure 5. I l lustrations of Metridia pacifica (female) 12 Figure 6. I l lustrations of Metridia pacifica (male) 13 Figure 7. Range (vertical lines) and means (crossbars) of 23 measurements on female specimens. Metridia pacifica (diagonal dashes) n = 35; M. lucens (solid line) n = 55; Metridia specimens from Indian Arm (horizontal dashes) n = 55. Figure 8. Range (vertical lines) and means (crossbars) of 24 measurements on male specimens. Metridia pacif ica (diagonal dashes) n = 35; M. lucens (solid line) n = 55; Metridia specimens from Indian Arm (horizontal dashes) n = 55. -VI-LIST OF FIGURES page Figure 9. Frequency histograms on selected body measurements 26 of Metridia pacif ica (diagonal hatching) n = 35; Metridia lucens (stippled) n = 55; and the Metridia specimens from Indian Arm (vertical hatching) n = 55. Females (A to D), males (E to F). Measurements in millimeters. Figure 10. Range and mean (crossbar) of the terminal setae on 27 the female P5 of Metridia pacif ica (diagonal hatching), Metridia lucens (stippled) and the Metri di a specimens from Indian Arm (vertical hatching). Measuremens in millimeters, n = 10. Figure 11. Total length of females plotted against prosome 29 length. Metridia pacifica (solid dots and dashed regression line) n = 35; Metridia lucens (triangles and dotted regression line) n = 55; and the Metridia specimens from Indian Arm (open c irc les and solid regression line) n = 55. 2 = more than one observation at that coordinate. Figure 12. Urosome length of females plotted against prosome 30 length. Symbols and sample sizes as for Fig. 11. Figure 13. Genital segment length plotted against prosome 31 length. Symbols and sample sizes as for Fig. 11. Figure 14. Genital segment depth plotted against prosome 32 length. Symbols and sample sizes as for Fig. 11. - v i i -LIST OF FIGURES page Figure 15. Urosome segment two length of females plotted 33 against prosome length. Symbols and sample sizes as for Fig. 11. Figure 16. Anal segment width of females plotted against 34 prosome length. Symbols and sample sizes as for Fig. 11. Figure 17. Block diagrams drawn to scale of female body 53 measurements. The length of each block represents the mean for that segment taken from Table 1. Figure 18. Segmentation of the male P5O for Metridia lucens 56 (A), the Metridia specimens from Indian Arm (B) and Metridia pacif ica (C) showing the structure and location of the f lexible seta (a), microprocess (b) and small spine (c). 500 X magnification. Figure 19. Variations in the structure of the female P5 of the 61 Metri di a specimens from Indian Arm (a, b, c) and Metridia lucens (d, e, f ) . Figure 20. Polarized light microscopy of the female f i f t h legs 63 of Metridia lucens (a, b, c) and Metridia pacif ica (d, e, f) showing variation in segmentation and birefringent musculature within each species. -v i i i -ACKNOWLEDGEMENTS I wish to express my sincere gratitude to the following people for their contribution towards this study. My supervisor, Dr. P.A. Dehnel for his patience and many valuable comments is most gratefully acknow-ledged. This work was supported in part by a grant to Dr. P.A. Dehnel. I appreciate the efforts by Dr. N.J. Wilimovsky for reviewing the manuscript and Mr. John Fulton, Fisheries and Marine Biological Station, Nanaimo, B.C. who also reviewed the manuscript and supplied specimens from Station P. I am deeply indebted to Dr. C.T. Shin and staff of the Invertebrate Zoology Department, National Museum, Ottawa, Ontario for granting laboratory space and providing Atlantic speci-mens. Many thanks are due Dr. B.W. Frost and Dr. D.M. Damkaer, Oceano-graphy Department, University of Washington who kindly provided speci-mens from Dabob Bay and for their expert counsel. I am obliged to Mr. Paul Whitfield for his stat ist ica l and computer capabi l i t ies. - 1 -INTRODUCTION The identif ication of the calanoid copepod Metridia pacif ica in the North Pacific as original ly described by Brodsky (1950), is con-trovers ia l . _M. pacif ica has been closely a l l ied to a similar species M. lucens which was original ly described by Boeck (1864). Brodsky has stated that j^. pacif ica is distributed in the North Pac i f ic , Sea of Japan, Sea of Okhotsk, Bering Sea and the Chukchi Sea while M_. lucens is distributed in the Atlantic, Indian Ocean, North Sea, Norwegian Sea and the Mediterranean Sea. The distribution of H. lucens in the North Atlantic has been i l lustrated by Lucas et al (1973, p 128). Until Brodsky's identif ication of M. pacif ica, the resident species off the coast of Brit ish Columbia was thought to be \A. lucens (Campbell, 1929; Davis, 1949). Some authors following Brodsky1s identif ication of M. pacif ica s t i l l refer to this species as M. lucens (Cameron, 1957; Le'gare, 1957, Mori, 1964). Using Brodsky's descrip-t ion, Shan (1962) refers to the Metridia species in Indian Arm, Brit ish Columbia, as possibly being M. pacifica but does so with reservation. Damkaer (1964) cited by Park (1968), and Beklemishev (1969) suggest that M. pacifica and M. lucens are synonymous. Vidal (1971) questions the identif ication of M_. pacif ica by Brodsky stating that specimens which he examined from the southern part of the Chukchi Sea also resembled _M_. lucens based on the number of spines on the male f i f t h leg. Giesbrecht (1892 p i . 33 Fig. 22) i l -lustrated _M. hibernica which Sars (1903) claims is synonymous with _M. lucens. A comparison of these drawings with M. pacifica and M. lucens in the present study shows s imi lar it ies to both species but there also appears to be some differences in the male f i f th leg. Sars also claims that Brady (1873) described M. lucens in his work on Brit ish copepoda - 2 -as Paracalanus hibernicus and at a later date recorded the same species under the name _M. armata. Giebrescht (1892) suggested that the furca (caudal ramus) of M. hibernica is shorter than the last abdominal segment. This does not agree entirely with the same comparisons in the present study on _M. pacif ica and M. lucens but most closely resembles _M. lucens. Tanaka (1963) compared Metridia from the Izu Region of Japan and suggested that they resemble _M. pacifica more than _M. lucens. Vinogradov (1968) showed vertical migrations of Mi. pacif ica in the Kurile-Kamchatka Trench while Gardner (1977) mentioned _M. pacifica as being distributed in the Strait of Georgia. The controversy concerning the identif ication of _M. pacif ica results from Brodsky's description of some of the distinguishing characteristics of this species when they are compared with _M. lucens. These distinguishing features include head shape, number of segments in the f i f t h leg of females, the length of the terminal brist les on the female f i f t h leg, caudal rami length in relation to anal segment length and the structure of the male f i f th legs. The present study has found that some of the descriptions are vague and not consistent with several specimens examined presumably of the same species and from one sample. The orientation of the male f i f t h leg is one example which will be discussed later. The character most often refuted by authors who question Brodsky's differentiation between _M. pacifica and M. lucens is the number of spines or spineform processes present on the fourth segment of the male f i f t h leg. Von Vaupel-Klein (1970) suggested that Brodsky is in error with his description of these spines and also with their specific location on the f i f th" leg and has since indicated he is convinced that M. pacifica and _M. 1ucens are the same species (Damkaer, pers. comm.). - 3 -My interest in Metridia was stimulated during the collection of copepods on oceanographic cruises along the coast of Brit ish Columbia including Indian Arm. Two species of Metridia having different body sizes were present in the plankton hauls and at certain times of the year made up the largest percentage of copepods collected. The larger species, M. okhotensis, was usually distributed at the deepest depths (below 200 m) while the smaller species was found 200 m to within 50 m of the surface, depending upon the time of sampling. Some characteris-t ics of the smaller species were similar to M_. pacif ica (Brodsky, 1950) while others were not. They appeared to be closer to the Metridia specimens in Indian Arm (Shan, 1962) but differed in certain aspects, even though some of the specimens used in the present study were sampled from Indian Arm. The i l lustrat ion of the terminal setae on the caudal rami of the female specimens (Shan, 1962 Fig. IX 1-3) shows them to di f fer in order of length from those observed in the present study. Geletin (1975) found two morphological forms of M. pacif ica in the Kurile area of the Pacific Ocean. They were distinguished by d i f -ferences in body length and the shape of the cephalothorax. He also stated that the large form was found in water temperatures from 2 - 9°C while the small form was found at 9 - 15°C. Geletin referred to these forms as Metridia N for the Northern large form and Metridia S for the Southern smaller form and suggested that the name J^l. pacif ica be re-tained until further investigations had been made. In i t i a l l y in this study the purpose was to compare the Atlantic form of Metridia believed to be M. lucens with a Pacific form believed to be _M. pacif ica. The Pacif ic form used for this comparison was sampled from Indian Arm. It became apparent, when Metridia from another Pacif ic location (Station P) was examined, that i t differed -. 4 -from the Indian Arm population in total length and shape of the cepha-lothorax in the same manner as the two forms in the Pacific described by Geletin. The Metridia sp. from Station P compared closely with the Northern large form while the Indian Arm specimens were similar to the Southern smaller form. The Northern large form best f i t s the descrip-tion of H. pacif ica by Brodsky. When females were visually compared between populations, \A. pacifica from Station P was found to be easily distinguishable from M. lucens which, along with other morphological differences, suggests that these species are not synonymous. The Indian Arm specimens appear most l ike J ^ . lucens but were found to differ in several ways as discussed in this study. It may possibly be a new species most closely related to _M. lucens and could be in part the reason for the past confusion between M. 1ucens and W. pacif ica. The present study morphologically compares H. lucens from the Atlantic with two populations of Metridia from the Pacific including another examination of the f i f th legs. Other distinguishing charac-ter i s t ics are introduced which indicate a dist inct morphological d i f -ference between H. lucens, M. pacif ica and the Indian Arm specimens. The results suggest that the Indian Arm specimens, also found in the Strait of Georgia and fjords along the coast of Brit ish Columbia and Washington, should neither be called H. pacifica nor M. lucens in accordance with the original descriptions of these species. MATERIAL AND METHODS Collection Specimens of _M. lucens were collected in the North Atlantic in the Bay of Fundy (Latitude 44°38.00' N, Longitude 66°35.00' W). The samples were collected on October 22, 1974 at 1959 hours in a bongo net - 5 -at a depth of 100 m and the specimens were preserved with 5 per cent formalin. The specimens of the Indian Arm population were collected near Vancouver, Brit ish Columbia (Latitude 49°25.50' N, Longitude 122°52.50' W). A vertical haul net having a diameter of 1 m was used to a depth of 200 m on November 6, 1974 at 1900 hours. The samples were preserved with 5 per cent formalin buffered with sodium borate. M. pacifica specimens were collected at the Canadian Weather Station P in the North Pacif ic (Latitude 50°N, Longitude 145°W). The specimens were collected at 2100 hours on March 11, 1970 with a vertical haul net at a depth of 4200 m. Samples were preserved with 5 per cent formalin. Sorting M. lucens and the specimens from Indian Arm were sorted by the author. M. lucens was sorted from preserved samples at the Inverte-brate Zoology Department of the National Museum at Ottawa, Ontario, and the Indian Arm specimens at the University of Brit ish Columbia. M. pacifica was sorted from plankton samples at the Fisheries and Marine Biological Station near Nanaimo, Brit ish Columbia. F i f t y - f i ve speci-mens of each sex for M. lucens and the Indian Arm specimens were selected to ensure as wide a size range as possible and to ensure that al l specimens were unflexed. A sample size of 35 was used for M_. pacif i ca . Each specimen was individually stored in a 1.0 dram vial containing 50 per cent glycerine and sea water and was assigned a serial number. Dissection and Slide Preparation Appendages were removed under a dissecting microscope using micro-forceps and insect pins. The tip of one pin was formed into a small hook for l i f t i n g appendages from the dissecting medium. Specimens were - 6 -dissected in 50 per cent glycerine and sea water, then the appendages transferred to the mounting medium of 100 per cent glycerine on a glass slide and cover s l ip for observation and measurement. Mounted appendages in glycerine that were kept for future observa-tion were sealed around the cover sl ip with clear fingernail polish. Although glycerine is not good for permanent slide preparations, i t is satisfactory for temporary preparations. Some specimens for permanent mountings were transferred from a formalin fixative through a graded ethanol series to 100 per cent and through two washings in xylene. They were then placed into Permount on a glass slide cover s l ip . During this procedure, all dissections were performed in xylene. Dehydration in alcohol and. xylene made the re-moval of appendages easier. The proximal segment of the appendages usually separated cleanly from the body. Other specimens were prepared for permanent mountings by transferring them from formalin directly into CMC-10 or 50:50 CMC-10 and CMC-S. CMC-10 is a water soluble, non-resinous mountant containing chloral hydrate, acetone and lact ic acid. CMC-S is composed of the same ingredients but with an additional staining constituent. Staining was sometimes done before dissection by placing several specimens in a solution of Chlorozol Black E and 50 per cent Lactic Acid. The staining period ranged from one to twenty-four hours, de-pending on the degree of staining required. Measurements A precalibrated ocular micrometer (scale 0-50) mounted in a com-pound microscope and another (scale 0-10) in a dissecting microscope were used for measurements. Measurements were recorded as micrometer units before converting to millimeters by multiplying the measurement - 7 -with a calibration factor determined for each magnification. Total length of the female specimens was measured under the dis-secting microscope at 32 X magnification with a precision of (+_ 0.083 mm). All other measurements were performed on the compound micro-scope. Male total length and prosome length for both sexes 20 X (+_ 0.024 mm); urosome length 50 X (+_ 0.011 mm); urosome segments including the anal segment and caudal rami 80 X (+_ 0.006 mm); second leg measure-ments 160 X (+0.004 nm) and f i f t h leg measurements 320 X (+0.002 mn). Total length and prosome length were measured from a lateral view (Fig. 1-1A, B). Total length (A) was measured from the rostrum to the posterior margin of the caudal ramus, excluding the caudal setae. Prosome length (B) was taken from the rostrum to the terminal point of the last thoracic segment. The depth of the female genital segment ( f i r s t urosomal segment) was also measured from a lateral view at i ts maximum depth (Fig. 1-3A). Length and width measurements of the female urosome segments including the caudal ramus, were taken from a dorsal view, (Fig. 1-4A to E). The length of the caudal ramus (F) was taken from the proximal jo int to the base of the two medial terminal setae. Caudal ramus width (G) was measured from the outside margin at the base of the seta located on the side of the segment, across to the opposite inner margin. Male urosomal measurements (Fig. 2-3A to D) were similar to those for females except width measurements were done only on the anal segment (F) and caudal ramus (H). - 8 -FIGURE 1. I l lustrations of the Metridia specimen (female) from Indian Arm, Brit ish Columbia. Description of measurements for al l female specimens (uppercase letters) . 1. Lateral aspect A- Total length B- Prosome length 2. Dorsal aspect (total length) 3. Last thoracic segment and genital segment (lateral aspect) A- Depth of genital segment 4. Urosome A- Genital segment (length) B- Segment two (length) C- Anal segment (length) D- Segment two (length) E- Anal segment (width) F- Caudal ramus (length) G- Caudal ramus (width) 5. Antennule 6. Second antenna 7. Maxilla 8. Mandible 9. Gnathobase 10. F i rs t maxilliped 11. Second maxilliped 12. F i rs t leg 13. Second Leg A- Coxopodite (width) B- Base of seta across coxopodite to joint with basi-podite C- Base of seta to rounded inner edge of the basipodite D- Rounded inner edge of basipodite to jo int with coxo-podi te E- Proximal exopodite segment (length) F- Proximal exopodite segment (width) G- Distal exopodite segment (length) 14. Third leg 15. Fourth leg 16. Fi fth leg A- Basipodite and f i r s t segment (combined length) B- F i rs t segment (length) C- Distal segment (length) D- Basipodite (width) E- Long seta (length) F- Medium seta (length) G- Short seta (length) METRIDIA SPECIMEN 9 (Indian Arm) - 9 -FIGURE 2. I l lustrations of the Metridia specimen (male) from Indian Arm, Brit ish Columbia. Description of measurements for a l l male specimens (uppercase letters) . Features of the f i f t h leg (lowercase letters) . 1. Lateral aspect (total length) 2. Dorsal aspect (total length) 3. Last thoracic segment and urosome (dorsal aspect) A- F i rs t urosome segment (length) B- Second urosome segment (length) C- Third urosome segment (length) D- Fourth urosome segment (length) E- Anal segment (length) F- Anal segment (width) G- Caudal ramus (width) H- Caudal ramus (length) 4. Geniculate antennule 5. Antepenultimate, penultimate and distal segments of the geniculate antennule 6. Second antenna 7. Maxilla 8. Mandible 9. Gnathobase 10. F i r s t maxilliped 11. Second maxilliped 12. F i r s t leg 13. Second leg 14. Third leg 15. Fourth leg 16. F i f th leg A- Basipodite (width) B- Segment P5O2 (length) C- Segment P5O5 (length) D- Macroprocess (chord length) E- Segment P5M5 (length) a- Flexible seta b- Microprocess c- Spine d- Macroprocess - 9a -METRIDIA SPECIMEN a* (Indian Arm) - 10 -FIGURE 3. I l lustrations of the Metridia lucens (female). 1. Total length (lateral aspect) 2. Total length (dorsal aspect) 3. Last thoracic segment and genital segment (lateral aspect) 4. Urosome (dorsal aspect) 5. Antennule 6. Second antenna 7. Maxilla 8. Mandible 9. Gnathobase 10. F i rs t maxilliped 11. Second maxilliped 12. F irst leg 13. Second leg 14. Third leg 15. Fourth leg 16. Fi fth leg METRIDIA LUCENS $ - 11 -FIGURE 4. I l lustrations of Metridia lucens (male). 1. Total length (lateral aspect) 2. Total length (dorsal aspect) 3. Last thoracic segment and urosome (dorsal aspect) 4. Geniculate antennule 5. Antepenultimate, penultimate and distal segments of the geniculate antennule 6. Second antenna 7. Maxilla 8. Mandible 9. Gnathobase 10. F i rs t maxilliped 11. Second maxilliped 12. F i r s t leg 13. Second leg 14. Third leg 15. Fourth leg 16. Fifth leg - 11a -METRIDIA LUCENS v0. - 12 -FIGURE 5. I l lustrations of Metridia pacifica (female). 1. Total length (lateral aspect) 2. Total length (dorsal aspect) 3. Last thoracic segment and genital segment (lateral aspect) 4. Urosome (dorsal aspect) 5. Second maxill iped 6. Gnathobase 7. Antennule 8. F i rs t leg 9. Second leg 10. Third leg 11. Fourth leg 12. Fi fth leg - 12a -METRIDIA PACIFICA - 13 -FIGURE 6. I l lustrations of Metridia pacif ica (male). 1. Total length (lateral aspect) 2. Total length (dorsal aspect) 3. Last thoracic segment and urosome (dorsal aspect) 4. Geniculate antennule 5. Second maxilliped 6. Gnathobase 7. Antepenultimate, penultimate and distal segments of the geniculate antennule 8. F i rs t leg 9. Second leg 10. Third leg 11. Fourth leg 12. Fi fth leg - 13a -METRIDIA PACIFICA - 14 -In Metridia, the adult male f i f t h leg (P5) is uniramus, asymmetri-cal (Figs. 2-16, 4-16, 6-12) and adapted for grasping the female for mating (Fleminger, 1967; Roff, 1972). The predominant feature of the male P5 is the long sickle-shaped process (Fig. 2-16d) which is part of, and extends from, the innner margin of the antepenultimate seg-ment. This process extends across to a smaller process (b) which is part of the fourth segment of the opposite P5. These processes, being extensions of the segments on which they are found, may be better not described as spines. The larger process will be referred to in this study as the macroprocess and the smaller one as the microprocess. The macroprocess was observed most often on the l e f t P5 of the Indian Arm specimens and on the right in M. lucens but i t was also observed to be reversed for both populations. In M. pacifica i t was observed an equal number of times on each side. The male geniculate antennule was always found on the same side of the specimen as the macroprocess on the P5 for each population. The male f i f t h leg in Metridia has been referred to by many authors as being either right or l e f t , which is now a vague description because of the present evidence of reversing asymmetry within the species. In the present study the leg on which the macroprocess is found is labelled P5M and the opposite leg P5O. A method of labell ing the male P5 to c lar i fy the identif ication and location of the various segments was deemed necessary because of the reversing asymmetry. With this method the macroprocess is always found on the P5M segment three (P5M3) whether i t is on the right or le f t leg. The P5O has five segments with the basipodite (Bp) identif ied as P5O1 and the other segments numbered sequentially to the distal seg-ment. The P5O5 on some specimens appeared to have additional segmenta-tion near i ts distal end. When this was observed i t was discounted as - 15 -a segment and believed to be a crease from a fold. The P5M also has f ive segments including the basipodite which, in terms of the P5M, is identif ied as P5M1. Although the basipodite may be identif ied as either P ^ i or P5O1, i t is solely for the correct identif ication of the two adjoining segments, namely P5M2 and P5O2. It will be referred to hereafter as the male P5BP. Measurements on the male P5 (Fig. 2-16A-G) for M. 1 ucens and the Indian Arm specimen include the maximum width of the P5BP (A), the chord of the macroprocess (D), the length of P5O2 (B), P5M5 (E) and P5O5 (C). The male P5 of H. pacifica was not measured because the orientation of the two legs and the macroprocess were in a different plane with each other. This made accurate measurements of these ap-pendages very d i f f i cu l t . An attempt to measure the P5 was abandoned because a large error in measurement could have been introduced. The female P5 was measured according to Fig. 1-16. The Bp and the adjoining proximal segment were measured over their combined length along the midline (A). The proximal segment was then recorded by i t -self for length (B). The distal segment was measured along its midline to the base of the terminal, medial seta. Some female specimens in a l l three populations showed a four-segmented P5 including the Bp. This was evident when the distal segment appeared to be divided and formed a small segment on which the terminal setae were attached. When this was observed, both small segments were measured together as one. This division of the distal segment was noticed in some specimens only under high magnification (800X). The lengths of two terminal setae (E and F) on the distal segment were measured and the Bp was also measured for width (D), similar to the measurement on the male P5BP. An additional ten specimens of _M. lucens, females, were selected for length measure-ments on the terminal setae of the P5- This was necessary for - 16 -comparison of al l three setae as some of the shortest setae (Fig. 1-16G) were broken on the M. lucens P5 used for regression analysis. The second leg (Pg) of males and females of Metridia has two small hooks on the inner margin of the f i r s t endopodal segment. This hami-form segment is a dist inctive characteristic of the genus (Brodsky, 1950; Mori, 1964) so the ?2 was used for morphological comparison between the Indian Arm specimens and M. 1 ucens. The structure of the ?2 is similar in both sexes, except being larger in the female (Fig. 1-13). It has a coxopodite, basipodite and a three-segmented exopodite and endopodite. There is a long seta with setules attached to the inner margin of the coxopodite which extends to the centre of the second endopodal segment. Other long setae, having setules, are attached to the inner margin of the exopodite and endopodite. The imbricated exopodite has a serrulate spine on the terminal end of the distal segment. Several measurements were recorded for the P2 (Fig. 1-13) of which one was the maximum width of the coxopodite (A). This measurement was taken across the segment from the position where the sclerite is at-tached. The distance was measured between the outside base of the seta on the coxopodite, across the segment to where i t joins the basipodite at their outer margin (B). From the same spot at the base of the seta, a measurement was taken to the peak of the Bp (C). From this point on the Bp another measurement was taken, again to where the coxopodite and basipodite join at their outer margin (D). The P2 exopodite was measured at three places for males and females. The antepenultimate segment was measured for length from where i t joins the Bp at the outer margin to where i t forms a point near the end of the segment (E). This point is found just below the - 17 -short spine (claw) which juts out from the distal end of the segment. The width of this segment was taken from the same distal point to where the antepenultimate and penultimate segments join at their inner margin (F). The distal segment was measured from the base of the terminal serrulate spine to where i t joins with the penultimate segment at their inner margin (6). There were no measurements taken on the endopodite. Stat ist ica l Analyses A sample size of f i f t y - f i ve was used for al l metasomal and uro-somal measurements on males and females of M. lucens and the Indian Arm specimens while a sample size of th i r ty - f ive was used for M. pacif ica. Measurements on the P2 and P5 were done with a sample size of ten. Analyses were carried out using the l ibrary program available on the computer system at the University of Brit ish Columbia with a 5 per cent probability level used for rejection of the null hypothesis. Individual characters were regressed against the prosome length established as the independent variable. This procedure was adopted from Frost (1971; 1974). Tests for the significance of the equality of slopes (H 0: bi=b2) and the equality of adjusted means (H 0: Y ^ ^ ) were determined from a one-way analysis of covariance. I l lustrations Drawings were made to scale using a camera lucida mounted on the compound microscope. Each subject was drawn with the maximum magnifi-cation which allowed i t to be viewed in whole. The total length of the female _M. paci f ica, being longer than M. lucens and the Indian Arm specimens required i t to be drawn at a magnification of 25X as compared with 38X for the two shorter specimens. It should be noted that the indication of the scale for the drawings of M. pacifica (Fig. 5-1, 2) - 18 -is shorter than for the Indian Arm specimens (Fig. 1-1, 2) and M. lucens (Fig. 3-1, 2). Polarized l ight microscopy on the female P5 of M. pacifica and M. lucens was done with a compound microscope equipped with a revolving stage. Al l drawings were reduced by photography. Frequency distribution histograms were plotted for some of the measurements on which there was a sample size of f i f t y - f i ve and th irty-f ive. The measurements which indicated the highest significant d i f -ference between sample means were selected for the histograms. Key Words aesthetascs - Long, slim, blunt, minute sensory process on copepod antennule. anal segment - Terminal urosome segment having pore for fecal excretion. antennae - (second antennae) Short biramous appendages which create water vortices for feeding, antennule - ( f i r s t antennae) Uniramous, long, slender appendage on the anterior of the cephalosome having sensory organs and occasionally used for locomotion, antepenultimate - Third last, apical - Pertaining to the t ip. basipodite - (=basipod) Distal segment of protopodite of a typical biramous appendage, biramous - Having two rami. br i s t le - Short, s t i f f hair or hair l ike microscopic projection. caudal rami - (=furca) Paired terminal processes on the distal end of the anal segment, cephalosome - (=forehead) Head or anterior region. - 19 -cephalothorax - Body division representing a fusion of one or more thoracic segments with the cephalosome. chord - Straight l ine joining two points on an arc, curve or circum-ference. copepodid - One of several instars preceding the sexually mature adult copepod. coxopodite - Basal segment of protopodite of a typical biramous appen-dage. distal - Farthest away from the base or point of attachment, dorsal - Pertaining to the back or upper surface, endopodite - Inner or median branch of a biramous appendage, exopodite - Outer or lateral branch of a biramous appendage, geniculate - (=prehensile) Adapted for grasping or seizing, genital segment - Proximal urosomal segment of females, gnathobase - Grinding edge of mandible for biting and chewing, hamiform - Hook shaped, imbricated - Overlapped. macroprocess - Long sickle-shaped process extending from the inner margin of the antepenultimate segment (P5M3) on the male f i f t h leg. microprocess - Short pointed process on the inner margin of the penultimate segment (P5O4) on the male f i f th leg. penultimate - Second last. pereiopods - Megs ) Paired appendages on most thoracic segments used for locomotion, seizing and handling food. plumose - Feathery; having a tuft of terminal subdivisions. prosome - (=metasome) Portion of copepod body which includes the cepha-lothorax and al l free thoracic segments. proximal - Near a point of reference or attachment. - 20 -rostum - Short pointed process at the anterior of the cephalosome. sc ler ite - Hard plate forming a portion of the exoskeleton between paired pereiopods. serrulate - Having small fine notches along the edge, seta (setae, pi.) - Needle-like projection of the exoskeleton. setules - Hair- l ike structures found on some setae. thorax - Segmented central portion of the body between the cephalosome and urosome. truncate - Having the extremity cut off, flattened, square or even, uniramous - Having one ramous. urosome - (=abdomen) Posterior region. RESULTS Synonymy 1864 Metridia lucens Boeck, sp. nov., Chr. Vid. Selsk. Forh. p. 238. 1873 (?) Paracalanus hibernicus Brady and Robertson, Ann. Mag. Nat. Hist., Vol. 12 (4). 1883 Metridia armata (?) Brady, Mon. Cope. Br i t . Is l., Vol. 8. 1892 Metridia hibernicus (?) Giesbrecht, XIX Mon. pel. Cope. pp. 345, 346. 1903 Metridia lucens Sars, Bergen Mus. pp. 113, 114 p i . LXXVII. 1948 Metridia lucens Brodsky, (vs. M. pacifica) Izv. Tik. Inst. Ryb. Kho. Okean., Vol 26. pp. 57-59, 96 p i . XIV. 1950 Metridia lucens Brodsky, Akd. Nauk. SSSR pp. 294, 295 Fig. 200. 1950 Metridia pacifica Brodsky, sp. nov., Akd. Nauk. SSSR pp. 295, 296 Fig. 201. 1963 Metridia pacifica Tanaka, Publ. Seto. Mar. Biol . Lab., Vol. XI (1) pp. 21, 22 Fig. 159. - 21 -1964 Metridia lucens (?) Mori, Pel. Cope. Neigh. Wat. Jap. pp. 67, 68 p i . 34 Figs. 1-5. 1970 Metridia pacifica von Vaupel-Klein, Zool. Verh. No. 110 pp. 30-33 Fig. 13b, c. 1971 Metridia lucens (?) Vidal, Univ. South. Cal i f . Dept. Biol. Sci. Tech. Report No. 5 pp. 88-91, 188. Figs. 142-143, 147, 148. 1975 Metridia pacifica Geletin, Sov. J . Ecol. Trans, from Ekologiya 6:3 pp. 68-72. 1924 Metridia sp. Esterly, (aff. Indian Arm Specimen) Univ. Ca l i f . Publ. Zool., Vol. 26 (5) pp. 96, 97 Fig. H. 1962 Metridia sp. Shan, M.Sc. Thesis Univ. Br i t . Col. pp. 32-40, 100-104 p i . VIII, IX. 1964 Metridia lucens (?) Damkaer, M.Sc. Thesis Univ. Wash. pp. 24-27. The range and means of selected characteristic measurements for the females (Fig. 7) and the males (Fig. 8) i l lustrate the differences as well as the s imi lar it ies between populations. Standard error was not included on these figures because i t was too small and could not be differentiated from the mean. Standard error along with the means of a l l body measurements and their 95 per cent confidence l imits are l i s ted for the females (Table 1) and males (Table 2). The P5 measure-ments are l i s ted for the females (Table 3) and males (Table 4). It should be noted that caudal rami width for the males is not included in Table 2. It was measured and found to be 0.064 mm on al l f i f t y - f i ve specimens from Indian Arm while the majority of measurements were 0.07 mm for _M. lucens. Neither the size of the specimen nor the length of the caudal rami had any effect on the width which seems un-rea l i s t i c and not characteristic of copepods. Because of the lack of variation for this measurement on these two populations, the width of - 22 -the caudal rami on M. pacifica males was not taken. The precision (+0.006 mm) and magnification (80X) at which the caudal ramus width measurements were taken can be improved which may provide more rea l i s t ic values for the males. The present results would produce zero slopes i f regressed against prosome length and the lack of variance allows no confidence limits to be placed on the measurements. Should the caudal rami widths be as observed in this study, then they would indicate a high degree of significance between the males. These results were not used for comparative purposes as another look at the male caudal rami width is warranted. The caudal ramus width in the females varied along with i ts length. H. paci f ica, having the longest mean length (Table 1) also showed a wider measurement than the Indian Arm specimens but was nar-rower than _M. lucens. The caudal rami in M. lucens tended to be shorter but wider than was observed on the Indian Arm specimens. The regression coefficients (intercepts and slopes, Tables 1-4) were determined by the least squares method of regression analysis. Significance tests (H 0: bi=b2) on the equality of slopes of regression lines (Table 5) revealed in the majority of cases that the slopes are not s ta t i s t i ca l ly different. The only body measurements in the females which showed slopes signif icantly different were for total length between _M. pacifica and _M. lucens. In the males, slopes were different for anal segment length, anal segment width and caudal rami length between _M. pacifica and the Indian Arm specimens and for anal segment length and anal segment width between M_. lucens and the Indian Arm specimens. The only body measurement on the male _M. lucens and Indian Arm specimens which was found to have a significant difference between their slopes was on the length of the fourth urosomal segment. The analysis of covariance on all measurements tested the equality - 23 -FIGURE 7. Range (vertical lines) and means (crossbars) of measurements on female specimens. Metricia pacifica (diagonal dashes) n = 35; M_. lucens (solid line) n = 55; Metridia specimens from Indian Arm (horizontal dashes) n = 55. A- Total length B- Prosome length C- Urosome length D- Genital segment length E- Genital segment depth F- Urosome segment two length G- Anal segment length H- Anal segment width I - Caudal ramus length - 24 -FIGURE 8. Range (vertical lines) and means (crossbars) of measurements on male specimens. Metridia pacifica (diagonal dashes) n = 35; M_. lucens (solid line) n = 55; Metridia specimens from Indian Arm (horizontal dashes) n = 55. A- Total length B- Prosome length C- Urosome length D- Urosome segment four length E- Anal segment length F- Anal segment width G - Caudal ramus length - 24a -2 .1« 1.5-» 1.0-S 2 . 0 -CO H 1.9-w H P w «i S 1.7-1.44 1.3H 1.2H i-H ll B -0 . 9 -0.8-0.7-0.64 0.16-, 0.14-1 0.12-4 0.10-1 0.08-1 D S • V •V s s E 1.6- l . O J 0.5- 0.06J - 25 -of the adjusted means (HQ'.Y i=Y 2 ) W l t n t h e majority of cases rejecting the null hypothesis (Table 6). The adjusted means on the female body measurements between M. lucens and the Indian Arm specimens indicate in a l l cases a significant difference between the populations. Between M. pacifica and _M. lucens, the adjusted means of body measurements ex-cept for anal segment length were signif icantly different, but only the urosome length and anal segment width were different between M_. pacif ica and the Indian Arm specimens. For the males, all adjusted group means of body measurements were s ignif icantly different between _M. pacif ica and _M. lucens. Caudal rami length was the only measurement not different between _M. pacifica and the Indian Arm specimens. Means for _M. lucens and the Indian Arm specimens showed a closer relationship with only the length of the third and fourth urosomal segments, width of the anal segment and length of the caudal rami being significantly different. Frequency histograms for body measurements on females (Fig. 9A-D) and males (Fig. 9E, F) i l lustrate a direct relationship with the means of the measurements. Although there is a certain amount of overlap in all cases, the histograms which best i l lustrate differences between the populations are on measurements having the highest significant di f -ference between their adjusted group means. The length measurements on the setae of the female P5 (Fig. 10) show each seta to be longest in M_. pacifica and shortest in the Indian Arm specimens. Regression Analyses - Females When plotted against prosome length, the measurements of each character fe l l along three regression l ines, each representing one of the three populations. On measurements for the females, most slopes of - 26 -FIGURE 9 . Frequency histograms on selected body measurements of Metridia pacifica (diagonal hatching) n = 3 5 ; Metridia lucens (stippled) n = 5 5 ; and the Metri di a specimens from Indian Arm (vertical hatching) n = 5 5 . Females (A to D), males (E and F). Measurements in millimeters. - 26a -A FEMALES 0.20 0.22 0.24 GENITAL SEGMENT DEPTH mm 30-, D FEMALES 0.070 0.082 0.094 CAUDAL RAMUS WIDTH mm 30-i 0.22 0.26 0.30 UROSOME SEGMENT 2 LENGTH mm 0.18 0.20 0.22 ANAL SEGMENT WIDTH mm E. MALES CO < Q 20J O 10J LU m 3 ' 0.116 0.128 0.141 0.153 UROSOME SEGMENT 4 LENGTH mm 0.128 0.141 0.153 CAUDAL RAMUS LENGTH mm - 27 -FIGURE 10. Range and mean (crossbar) of the terminal setae on the female P5 of Metridia pacifica (diagonal hatching), Metridia  lucens (stippled) and the Metri di a specimens from Indian Arm (vertical hatching). Measurements in millimeters, n = 10. - 27a -- 28 -the regression lines were s tat i s t ica l ly identical but the majority of adjusted means were signif icantly different between populations. A l -though a significance between populations was indicated in many cases, only those regression plots which best i l lustrate the difference were selected. Plots of the females, total length (Fig. 11) and urosome length (Fig. 12) are similar between the populations in respect to their scatter diagrams. The genital segment, (Fig. 13), has s ta t i s t i ca l l y different adjusted group means between M. pacifica and M. 1ucens and the Indian Arm specimens but not between _M. pacif ica and the Indian Arm specimens. The scatter diagrams for \A. 1ucens and the Indian Arm specimens overlap more than observed for the total length or urosome length plots. The overlap of segment lengths between populations is also shown on the i l lustrat ion of ranges and means of measurements (Fig. 7). Genital segment depth (Fig. 14) also has an overlap in the cluster diagrams which occurs between 1.75 and 1.88 mm on the prosome length between the Indian Arm specimens and M. lucens. The scatter diagram for M. pacif ica is farthest away from the diagram for the Indian Arm specimens but also has good separation from M. lucens. The points of the scatter diagrams i l lustrate that M. lucens has a genital segment which has more depth than is found in hi. pacifica and the Indian Arm specimens even though its prosome length fa l l s in the mid range. The equality of the regression slopes for the genital segment depth between al l three populations is not signif icant. The length of the second urosomal segment when plotted against prosome length (Fig. 15) forms three nonoverlapping clusters. The slopes of the regression lines are not signif icantly different but the difference in the adjusted group means of the length measurements is highly significant between M. pacifica and W. lucens and also M. lucens - 29 -FIGURE 11. Total length of females plotted against prosome length. Metridia pacifica (solid dots and dashed regression line) n = 35; Metridia lucens (triangles and dotted regression line) n = 55; and the Metridia specimens from Indian Arm (open c i rc les and solid regression line) n = 55. 2 = more than one observation at that coordinate. - 30 -I FIGURE 12. Urosome length of females plotted against prosome length. Symbols and sample sizes as for Fig. 11. - 30a -1.20_ - 31 -FIGURE 13. Genital segment length plotted against prosome length. Symbols and sample sizes as for Fig. 11. - 31a -0.48 _ , PROSOME LENGTH mm - 32 -FIGURE 14. Genital segment depth plotted against prosome length. Symbols and sample sizes as for Fig. 11. - 32a -0.26 _ E E X 0.24. I -Q_ U l Q h-Z u i U 0 22 CO _i < I— • a 0.20J 0.18. A A2 A A © ©2 A , A A2 A A^-A*2 « 2 • • ^ • 2 " 0 2 « 2 A2 A2,A£ A2 1. O O © „ < J ^ © A A " " ^ # 2 • • *» O © 0 A A A 0 2 \ 0 2 j y ^ X 5 Q > 2 © O O 0 2 0 O O 02 I 1 1 -1.8 1.9 2.0 PROSOME LENGTH mm I 2.2 1.6 1.7 2.1 - 33 -FIGURE 15. Urosome segment two length of females plotted against prosome length. Symbols and sample sizes as for Fig. 11. UROSOME SEGMENT 2 LENGTH mm, o p p P P o> o J> * ^ - 34 -FIGURE 16. Anal segment width of females plotted against prosome length. Symbols and sample sizes as for Fig. 11. / - 34a -0.20 _ 0.18 J E' E £ 0.16 J l-UJ w 0.14. < z < 0.12 J 0.10. "~1 2.2 1.6 1.7 - i : 1 r-1.8 1.9 2.0 PROSOME LENGTH mm 2.1 - 35 -and the Indian Arm specimens but not between M. pacifica and the Indian Arm specimens. The comparison between the three populations on the lengths of their second urosomal segments in terms of the separation of their cluster diagrams and their adjusted group means shows i t to be one of the best characters for distinguishing between the females. The slopes produced by the regression analysis using anal segment width as the dependent variable (Fig. 16) are s tat i s t ica l ly the same. The scatter diagrams show good separation, especially between M. pacifica and the other two populations. The t-test on the adjusted group means of the anal segment width indicates a difference between the populations as being highly signif icant. The caudal ramus length, l ike the length of the second urosomal segment, is one of the best characters for distinguishing between M. pacifica and M. lucens and also _M. lucens and the Indian Arm specimens when comparing their regression slopes and adjusted means. The d i f -ference between the adjusted means of J^J. pacif ica and the Indian Arm specimens is not significant for the length of the caudal rami (Table 6). Analysis of covariance were performed on the female P5 measure-ments (Table 3). The regression analysis produced clusters (not in-cluded) that were widely scattered because of the small sample size. There was separation between some of the scatter diagrams but the re-gression lines in most cases did not appear to be indicative of the population they represented. An outl ier in some scatter diagrams caused the regression l ine to be directed away from the main cluster. In three diagrams for M. pacif ica (measurements D, E and F) the out-l ier s caused the regression lines to have negative slopes. The best separation between the three populations found on the P5 was on measurements of the terminal setae but the small sample size and the - 36 -negative slopes for some regression lines was decisive for not in -cluding the regression plots. Most of the female P5 measurements, i f done using a large sample size may be good indicators for separation of the populations in this study. Regression analysis on the female P2 did not produce results which separated the populations as well as the P5 measurements. There was only one case where a significant difference was found in the adjusted group means (measurement C) between _M. lucens and the Indian Arm speci-mens. Two nonoverlapping clusters were formed from the regression analysis of this measurement but for reasons as for the P5 measure-ments, the regression plots were not included. Also, because of these reasons, measurements on the P2 of M. pacif ica were not taken. Regression Analyses - Males Differences in the males between populations were not as plentiful nor as obvious as for the females. For the males, measurements on the anal segment length and width and the length of the third and fourth urosomal segments were the best for distinguishing between the popula-tions. The slope of the regression l ine on the anal segment width for the Indian Arm specimens, however, was not s ignif icantly different from zero and the scatter diagrams were almost completely overlapped. Most of the body measurements on the males, except for those previously mentioned, were very similar between the populations. The cluster diagrams and regression lines were not satisfactory for distinguishing between the populations, so were not included. The similar range in size of the prosome between the males did not provide separation in the cluster diagrams. It should be noted that the prosome length in the male _M. pacif ica was shorter than that observed for _M. lucens and the Indian Arm specimens. This is contrary to the prosome length in the - 37 -females which was found to be signif icantly larger for hi. pacif ica. Significance tests on the adjusted group means of the body measurements for the males (Table 6) show a high degree of significance between M. pacif ica and M. lucens for all measurements. This was also evident between M. pacifica and the Indian Arm specimens except for the measurement on the length of the caudal rami. Differences between _M. 1ucens and the Indian Arm specimens were not as numerous as a s i gn i f i -cance between these populations was found only for measurements on the third and fourth urosomal segments, anal segment width and the length of the caudal rami. The P5 measurements for the males (Table 4) were performed only on M. lucens and the Indian Arm specimens. Some of these measurements were found to be signif icantly different when the adjusted group means were compared. These measurements (B, C, D and E) when compared by their regression plots (not included) showed good separation in the scatter diagrams for C and E but the slopes of the regression l ine for the Indian Arm specimens in both cases were s tat i s t ica l ly not different from zero. Like the female P5 measurements, those done on the male P5 could l ikely be good indicators for comparing between _M. lucens and the Indian Arm specimens using regression plots i f a large sample size is used. Using the P5 in Metridia for distinguishing between the popula-tions by comparing length measurements is tedious and time consuming. The P5 of the populations examined in the present study is small when compared with another calanoid copepod such as Calanus plumchrus and examination and measurements are d i f f i cu l t because of the variation in the orientation of the male P5 as observed in H. pacif ica. Measurements were taken on the male ?2 f°r lucens and the Indian Arm specimens but stat ist ica l results indicated that most of - 38 -them were not s ignif icantly different. All the slopes of the regres-sion plots (not included) for the male P2 were not signif icantly dif-ferent and only three adjusted group means of measurements B, E and F (Fig. 1-13) were found to be different between the populations. There were no P2 measurements done on the male of M. pacif ica. The probability of a common slope being zero between populations for the regression plots selected on a sample size of 55 is less than 0.001 for females and males. The P2 and P5 measurements for both sexes show the probability of the common slope being zero as ranging from 0.002 to 0.656 which is attributed to the small sample size of 10. Drawings of M. paci f ica, M. lucens and the Indian Arm specimens i l lustrate dorsal and lateral views and al l appendages used for swimming. All feeding appendages are included for M. lucens and the ' Indian Arm specimens while only some are included for M. paci f ica. The scale of the drawings are included for the three populations. The location of the measurements as described in the material and methods are shown only for the females (Fig. 1) and the males (Fig. 2) in the Indian Arm population. These measurements were identical ly taken on M_. lucens and M. pacifica except for the P2 and P5 measurements which were not measured in M. pacif ica. The drawing of the male P3 in the Indian Arm specimen (Fig. 2-14) appears larger than the P4 (Fig. 1-15). This is because the P3 used for the drawing was taken from a larger specimen. The other legs were taken from the same smaller specimen. It should be noted that the P3 and P4 on the specimens observed are different in structure as well as s ize. The P4, which is longer than the P3, has seven setae on the distal segment of the endopodite while the P3 has eight setae. There is another morphological feature not previously described for Metridia which was found on the three - 39 -populations in this study. A small setae, having setules, was found on the P]_. This seta, located near the distal end and attached near the inner margin of the basipodite, has a hook on its free end which re-sembles a shepherd's crook. Because of i ts small size i t was or ig inal -ly overlooked on specimens of M. lucens and those from Indian Arm as i t was f i r s t discovered on _M. pacif ica. The hooked seta was also found on M. lucens and the Indian Arm specimens when they were re-examined. The extra seta on the endopodite of the P3 as well as the hooked seta on the P]_ is evident on all three populations including both sexes. - 40 -TABLE 1. Female body measurement stat ist ics from analysis of covariance. Intercepts and slopes derived by the regression of measurements against prosome length. Metridia pacifica n=35 Measurement X + 95% CL Y a b Total (L) 3.215 + 0.039 3.040 0.020 0.0735 1.5125 Urosome (L) 1.085 T 0.020 1.000 0.010 -0.1423 0.5909 Genital seg. (L) 0.441 T 0.010 0.415 0.005 -0.0429 0.2330 Genital seg. (D) 0.222 T 0.004 0.207 0.002 0.0425 0.0864 Uro. seg. 2 (L) 0.278 T 0.008 0.259 0.004 -0.0458 0.1559 Uro. seg. 2 (W) 0.165 T 0.005 0.159 0.003 0.0379 0.0612 Anal seg. (L) 0.173 T 0.006 0.160 0.003 0.0758 0.0468 Anal seg. (W) 0.185 T 0.004 0.172 0.002 0.0548 0.0627 Caudal rami (L) 0.221 T 0.006 0.203 0.003 -0.0226 0.1173 Caudal rami (W) 0.089 T 0.003 0.085 0.002 0.0730 0.0077 Prosome (L) 2.077 T 0.015 Metridica lucens n=55 Total (L) 2.816 + 0.017 2.813 0.009 1.2191 0.8374 Urosome (L) 0.962 T 0.009 0.961 0.004 0.1223 0.4403 Genital seg. (L) 0.391 T 0.005 0.391 0.002 0.1662 0.1179 Genital seg. (D) 0.218 T 0.002 0.217 0.001 0.0212 0.1032 Uro. seg. 2 (L) 0.219 T 0.003 0.218 0.002 -0.0032 0.1165 Uro. seg. 2 (W) 0.167 T 0.002 0.167 0.001 0.0844 0.0433 Anal seg. (L) 0.167 T 0.003 0.166 0.001 0.0129 0.0808 Anal seg. (W) 0.206 T 0.002 0.206 0.001 0.0269 0.0939 Caudal rami (L) 0.183 T 0.002 0.182 0.001 -0.0128 0.1027 Caudal rami (W) 0.093 T 0.001 0.093 0.001 0.0266 0.0348 Prosome (L) 1.097 T 0.019 Metridia specimen (Indian Arm) n=55 Total (L) 2.845 + 0.027 2.959 0.014 0.8181 1.1311 Urosome (L) 0.988 T 0.014 1.043 0.007 0.0140 0.5435 Genital seg. (L) 0.401 + 0.007 0.418 0.004 0.0912 0.1729 Genital seg. (D) 0.199 T 0.003 0.209 0.001 0.0938 0.0587 Uro. seg. 2 (L) 0.251 T 0.005 0.263 0.003 0.1256 0.0700 Uro. seg. 2 (W) 0.155 T 0.004 0.160 0.002 0.1315 0.0131 Anal seg. (L) 0.147 T 0.004 0.155 0.002 0.0081 0.0775 Anal seg. (W) 0.184 T 0.003 0.192 0.002 0.0985 0.0477 Caudal rami (L) 0.198 T 0.004 0.209 0.002 0.0328 0.0922 Caudal rami (W) 0.080 T 0.002 0.083 0.001 0.0590 0.0177 Prosome (L) 1.792 T 0.013 L=Length, D=Depth, , w=Width, X=group mean, CL=confidence l imits, Y=adjusted group mean, Sy=standard error, a=intercept, b=slope. - 41 -TABLE 2. Male body measurement stat ist ics from analysis of covariance. Intercepts and slopes derived by the regression of measurements against prosome length. Metridia pacifica n=35 Measurement X + 95% CL Y SX a b Total (L) 1.870 + 0.012 1.884 0.006 0.0481 1.4938 Urosome (L) 0.711 T 0.009 0.716 0.005 -0.0227 0.6034 Uro. seg. 1 (L) 0.091 +" 0.002 0.092 0.001 0.0300 0.0502 Uro. seg. 2 (L) 0.135 T 0.003 0.137 0.002 0.0129 0.1216 Uro. seg. 3 (L) 0.129 T 0.002 0.130 0.001 0.0031 0.1035 Uro. seg. 4 (L) 0.129 T 0.002 0.130 0.001 -0.0321 0.1325 Anal seg. (L) 0.093 T 0.002 0.094 0.001 0.0187 0.0611 Anal seg. (W) 0.122 T 0.002 0.123 0.001 0.0366 0.0702 Caudal rami (L) 0.145 +" 0.002 0.145 0.001 -0.0386 0.0875 Prosome (L) 1.216 T 0.019 Metridica lucens n=55 Total (L) 1.948 + 0.010 1.929 0.005 0.4615 1.1988 Urosome (L) 0.752 T 0.007 0.745 0.004 0.1597 0.4777 Uro. seg. 1 (L) 0.099 T 0.002 0.098 0.001 0.0540 0.0363 Uro. seg. 2 (L) 0.144 T 0.002 0.144 0.001 -0.0399 0.1483 Uro. seg. 3 (L) 0.136 T 0.002 0.134 0.001 0.0369 0.0799 Uro. seg. 4 (L) 0.136 T 0.002 0.135 0.001 0.0446 0.0737 Anal seg. (L) 0.101 T 0.002 0.100 0.001 -0.0188 0.0966 Anal seg. (W) 0.143 +" 0.001 0.142 0.001 0.0765 0.0536 Caudal rami (L) 0.137 T 0.002 0.136 0.001 0.0560 0.0653 Prosome (L) 1.240 T 0.011 Metridia specimen (Indian Arm) n=55 Total (L) 1.921 + 0.010 1.931 0.005 0.3213 1.3188 Urosome (L) 0.752 T 0.007 0.755 0.004 0.1984 0.4564 Uro. seg. 1 (L) 0.097 T 0.002 0.097 0.001 0.0101 0.0716 Uro. seg. 2 (L) 0.143 T 0.002 0.144 0.001 0.0532 0.0740 Uro. seg. 3 (L) 0.140 +" 0.002 0.141 0.001 0.0154 0.1027 Uro. seg. 4 (L) 0.144 T 0.002 0.144 0.001 0.0282 0.0955 Anal seg. (L) 0.097 T 0.002 0.098 0.001 0.0789 0.0149 Anal seg. (W) 0.139 T 0.001 0.140 0.001 0.1328 0.0051 Caudal rami (L) 0.147 T 0.002 0.147 0.001 0.1076 0.0325 Prosome (L) 1.213 T 0.013 L=Length, D=Depth, W=Width, X=group mean, CL=confidence l imits , Y=adjusted group mean, Substandard error, a=intercept, b=slope. - 42 -TABLE 3. Female f i f th leg measurement stat ist ics from analysis of covariance. Intercepts and slopes derived by the regression of measurements against prosome length. Metridia pacifica n=10 Measurement X + 95% CL Y SX a b A 0.148 + 0.008 0.140 0.004 0.0466 0.0488 B 0.062 + 0.003 0.059 0.001 -0.0209 0.0399 C 0.039 + 0.007 0.035 0.003 0.0806 -0.0200 D 0.121 + 0.006 0.116 0.003 0.2135 -0.0445 E 0.136 + 0.013 0.128 0.007 0.3390 -0.0977 F 0.108 + 0.009 0.103 0.004 0.0939 0.0068 Prosome 2.078 Metridica lucens n i=10 A 0.133 + 0.006 0.133 0.003 0.0410 0.0477 B 0.056 + 0.002 0.056 0.001 0.0267 0.0152 C 0.051 + 0.004 0.051 0.002 -0.0140 0.0337 D 0.118 + 0.004 0.118 0.002 0.0343 0.0434 E 0.160 + 0.009 0.159 0.005 0.0297 0.0676 F 0.123 + 0.006 0.123 0.003 0.0771 0.0238 Prosome 1.928 Metridia specimen (Indian Arm) n=10 A 0.110 + 0.008 0.118 0.004 -0.0086 0.0673 B 0.050 + 0.003 0.052 0.001 0.0361 0.0079 C 0.038 + 0.007 0.042 0.003 0.0105 0.0156 D 0.098 + 0.006 0.103 0.003 0.0400 0.0329 E 0.104 + 0.014 0.112 0.007 -0.0512 0.0881 F 0.088 + 0.009 0.093 0.005 -0.0625 0.0854 Prosome 1.762 X=group mean, CL=confidence l imits , Y=adjusted group mean, S-^ = error, a=intercept, b=slope. - 43 -TABLE 4. Male f i f t h leg measurement stat ist ics from analysis of covariance on Metridia lucens and the Metridia specimen from Indian Arm. Intercepts and slopes derived by the regression of measurements against prosome length. Metridica lucens n=10 Measurement X + 95% CL Y a b A 0.126 + 0.003 0.126 0.001 0.1026 0.0193 B 0.071 + 0.003 0.070 0.001 0.0009 0.0564 C 0.204 + 0.004 0.204 0.002 0.1646 0.0320 D 0.184 + 0.007 0.183 0.003 0.0921 0.0739 E 0.201 + 0.005 0.201 0.002 0.0983 0.0834 Prosome 1.237 + 0.027 Metridia specimen (Indian Arm) n=10 A 0.125 + 0.003 0.127 0.001 0.0821 0.0357 B 0.063 + 0.002 0.064 0.001 0.0358 0.0229 C 0.185 + 0.004 0.185 0.002 0.1810 0.0035 D 0.170 + 0.005 0.170 0.003 0.1126 0.0471 E 0.176 + 0.004 0.177 0.002 0.1521 0.0200 Prosome 1.207 + 0.046 X=group mean, CL=confidence l imits, Y=adjusted group mean, Substandard error, a=intercept, b=slope. TABLE 5. - 44 -Tail area probability of t-tests between slopes ( b ^ ^ ) for body measurements of female and male Metridia specimens. FEMALE pac. pac. vs. vs. luc. I.A. Total (L) 0.02 0.15 Urosome (L) 0.25 0.78 Uro. seg. 1 (L) 0.10 0.45 Uro. seg. 1 (D) 0.58 0.29 Uro. seg. 2 (L) 0.37 0.20 Uro. seg. 2 (W) 0.63 0.19 Uro. seg. 3 (L) Uro. seg. 4 (L) Anal seg. (L) 0.45 0.51 Anal seg. (W) 0.33 0.58 Caudal (L) 0.71 0.57 Caudal (W) 0.20 0.86 MALE luc. pac. pac. 1 uc. vs. vs. vs. vs. I.A. luc. I.A. I.A. 0.21 0.06 0.27 0.42 0.36 0.30 0.18 0.86 0.37 0.48 0.51 0.27 0.06 0.29 0.50 0.15 0.07 0.31 0.47 0.98 0.43 0.05 0.23 0.44 0.93 0.24 0.05 0.00 0.08 0.42 0.00 0.05 0.75 0.41 0.05 0.22 0.21 L=Length, W=Width, D=Depth, pac.=M. pacif ica, luc.=M. lucens and I.A.=Metridia specimen from Indian Arm. - 45 -TABLE 6. Tail area probability of t-tests between adjusted group means (Y1=Y2) for body measurements of female and male Metridia specimens. FEMALE MALE pac. pac. luc. pac. pac. 1 uc. vs. vs. vs. vs. vs. vs. luc. I.A. I.A. luc. I.A. I.A. Total (L) 0.00 0.78 0.00 0.00 0.00 0.99 Urosome (L) 0.00 0.01 0.00 0.00 0.00 0.09 Uro. seg. 1 (L) 0.00 0.18 0.00 0.00 0.00 0.44 Uro. seg. 1 (D) 0.00 0.36 0.00 Uro. seg. 2 (L) 0.00 0.88 0.00 0.00 0.00 0.78 Uro. seg. 2 (W) 0.00 0.81 0.00 Uro. seg. 3 (L) 0.01 0.00 0.00 Uro. seg. 4 (L) 0.00 0.00 0.00 Anal seg. (L) 0.09 0.33 0.00 0.00 0.00 0.10 Anal seg. (w) 0.00 0.00 0.00 0.00 0.00 0.02 Caudal (L) 0.00 0.37 0.00 0.00 0.15 0.00 Caudal (w) 0.00 0.07 0.00 L=Length, w=width, D=Depth, pac.=M. paci f ica, luc.=M. lucens and I.A.=Metridia specimen from Indian Arm. - 46 -DISCUSSION The ranges and means of selected measurements on the females (Fig. 7) i l lustrate the larger size of _M. pacif ica when compared with the other two populations. This is particularly evident for total length, prosome length, urosome length, urosome segment 2 length and the length of the caudal rami. The only measurement in which H. pacif ica does not have the highest mean is for the width of the anal segment which is highest on M. lucens (Fig. 7-H). A comparison between females of _M. lucens and the Indian Arm specimens shows them to have a similar mean for total length (Fig. 7-A) but differ according to the length of their prosomes and urosomes. \A. lucens shows the higher mean for prosome length (Fig. 7-B) while the higher mean for urosome length (Fig. 7-C) is found on the Indian Arm specimens. The length of the second urosomal segment is characteristic between these populations as i t s mean length is much higher on the Indian Arm specimens (Fig. 7-F). The second urosomal segment along with the length of the caudal rami contribute most to giving the Indian Arm specimen the longer urosome than is found on M. lucens. When the three populations are compared by the adjusted group means of their body measurements (Table 6), the ta i l area probability of the t-tests shows that female M. pacif ica and M. lucens are s i gn i f i -cantly different for al l measurements except anal segment length. M. lucens and the Indian Arm specimens show a difference on the width of their anal segments and length of their urosomes. The ranges and means of selected measurements on the males (Fig. 8) shows there is not as much of a size difference between the males as was found between the females. Unlike total length in the females, the male of M. pacifica was found to have the lowest mean length (Fig. - 47 -8-A). The lower mean lengths for the male M. pacifica was also evident for most other measurements and especially on the width of the anal segment (Fig. 8-F). The means of the male anal segment widths show a similarity to that found in the females with the higher mean being that of H. lucens. Caudal rami length (Fig. 8-G) as was found on the females shows ML lucens having the lowest mean. The student's t-test on the adjusted group means of male body measurements (Table 6) showed them all as being signif icantly different between M. pacifica and M. 1ucens. The same tests between M. pacifica and the Indian Arm specimens showed al l measurements except for caudal rami length to be signif icantly different. When H. lucens and the Indian Arm specimens were similarly compared, only the length of the third and fourth urosomal segments, width of the anal segment and length of the caudal rami were found to be different between the popu-lations. Although many of the measurements show differences between the males based on the adjusted group means, the similarity between their arithmetic means suggests that distinguishing between the males on the basis of their body measurements may not be acceptable as a method for separating the male populations. Regression analyses on the males for these measurements, because of their similar prosome lengths produced scatter diagrams which completely overlapped in most cases and there was no significant difference between the slopes. The curvature in lateral prof i le of the cephalosome from the f i r s t metasomal segment to the rostrum may be used as a distinguishing characteristic. This feature which is most pronounced in the females has been used by Frost (1974) for separating sibling species of Calanus, by Woodhouse (1971) and by Shan (1962). Brodsky (1950) also used headshape of _M. pacif ica when differentiating between i t and _M. lucens. The present study shows the headshape of ^ . pacifica females - 48 -(Fig. 5-1) to be similar to the diagram by Brodsky (1950, Fig. 201). The headshape of the specimens from Indian Arm (Fig. 1-1) appear to be sl ightly less convex giving them a more rounded appearance than M. pacif ica and is in agreement with Shan when comparing his lateral aspect of Metridia sp. (Shan, 1962 Fig. IX-7). The forehead of _M. pacif ica (Fig. 5-1) when compared with that of lucens (Fig. 3-1) appears to be more convex or blunter. The lateral view of _M. lucens shows a more curving profi le from the rostum to the terminal points on the thoracic segment, while M. pacifica and the Indian Arm specimens tend to flatten out along the dorsal outline. This dorsal outline was not consistent with all specimens within the same population but was the norm. The lateral profi les of the males in this study, conform with the drawings by Sars (1903 pi. LXXVII). A Metridia population from San Francisco Bay is suggested as being either M. boecki (Giesbrecht, 1892) or M. lucens (Esterly, 1924) but also appears similar to the Indian Arm specimens in respect to head-shape and lateral prof i le. The lateral profi le of M. boecki (Brodsky, 1950 Fig. 201) is quite different from the Indian Arm specimen which suggests that M. boecki is not found in Indian Arm. The female Indian Arm specimens and _M. lucens were also found to differ from M. boecki by the shape of the ventral side of the genital segment. The Indian Arm specimens and _M. lucens have a well defined bulge at the location of the genital pores on this segment (Fig. 1-1, 3) while M. boecki (Brodsky, 1950 Fig. 202 after Sewell, 1932) does not. Giesbrecht (1895) believed that M. boecki and _M. lucens are different species. _M. boecki and M. lucens can be separated by specific segment measurements and also according to their distr ibution. M. boecki has been reported in Curruca Bay in the South Pacif ic (Giesbrecht, 1895). - 49 -If the shape of the genital segment is a distinguishing charac-ter i s t i c between _M. boecki and the populations in this study then _M. boecki is not the species found in San Francisco Bay. The possibi l i ty of M. boecki being in San Francisco Bay was suggested by Esterly (1924) but the California population is shown as having a well defined bulge at the genital pores (Esterly, 1924 Fig. H-4) which distinguishes i t from M_. boecki. This is providing that the i l lustrat ion of M. boecki (Brodsky, 1950 Fig. 202) is accurate. The California population and the population from Indian Arm were presented by Shan (1962) as having differences. This suggests that these populations are dist inct but an indepth study of the California population should be done before the relationship between i t and the populations in the present study can be determined. Brodsky (1950) suggests that the population in San Francisco Bay could be M. pacif ica but this does not agree with the present study. There are differences in the structure of the male f i f th leg between specimens from San Francisco Bay, M. pacifica and the Indian Arm specimens. The main difference is the size of the microprocess which is larger in the drawing by Esterly than was observed on the populations in the present study. The shape of the lateral angles of the last thoracic segment is mentioned by Mori (1964) as being a suitable character to separate species. He mentioned that NL lucens is found in the Pacific Ocean around Japan but his description of the Japanese population suggests that i t may be synonymous with the Indian Arm population. His drawing of the male (Mori, 1964 p i . 34-1), particularly the shape of the last thoracic segment, is not in agreement with the present study nor with previous drawings of this same segment for W\. lucens and _M. pacif ica by other authors. This segment in Mori's drawing from a dorsal view, is - 50 -broad over the majority of the length and does not taper towards the thoracic points as found for the specimens in the present study. Tanaka (1963) i l lustrates KL pacifica from Japan and his presentation of the last thoracic segment in the males (Tanaka, 1963 Fig. 159-b) conforms with M. pacifica (Fig. 5-3) and is also similar to the Indian Arm specimens (Fig. 2-3). The other drawings (Mori, 1964 p i . 34) and descriptions of the Metridia from Japan appear to be more l ike the specimens found in Indian Arm and not M. lucens as he suggests. His drawing of the entire length of the female _M. lucens in a dorsal view (Mori, 1964 p i . 34-4) is more l ike the Indian Arm specimens and also his drawings of the male and female P5. His i l lus trat ion of the female P5 does not show the inner terminal seta on the distal segment as being much longer than the other setae. This indicates that the P5 used for his drawing was not from M^ lucens. Mori (1964) stated that the furcal style (caudal rami) is about twice as long as wide. An examination of the caudal rami in his drawing of the female shows them to be 2.5 times longer than wide which indicates i t as not being _M. lucens. The length to width ratio (Fig. 1-4 F/G) of the caudal rami for M. pacif ica is reported as being 2.5 times longer than wide (Brodsky, 1950; Tanaka, 1963) and supported by the present study for _M. pacif ica and also for the Indian Arm speci-mens. The length to width ratio of the caudal rami for J*1. lucens in this study was similar to that found for M. lucens (Sars, 1903) which was twice as long as wide. The lateral prof i le of the genital segment of ]4. pacif ica (Tanaka, 1963 Fig. 159-b) agrees with a similar drawing (Fig. 5-3) in the present study. The ventral side of the segment appears to have a more pronounced bulge at the genital pores in M. pacifica and also the - 51 -Indian Arm specimens (Fig. 1-3) than is found in NL lucens (Fig. 3-3). M_. lucens has the greater depth of the genital segment (Table 1; F ig. 7-E) compared with the Indian Arm specimens but also appears to be comparatively deeper in depth over the whole segment. The depth of the genital segment is similar between W. lucens and _M. pacifica (Fig. 7-E). The length ratio between the anal segment and the caudal rami for M_. pacif ica and M. lucens has been described by other authors (Esterly, 1924; Brodsky, 1950; Shan, 1962) with varying ratios reported. In the present study, the caudal rami were found to be nearly equal in length to the anal segment for M. lucens but the same comparison in the Indian Arm specimens revealed them to be up to 1.5 times longer. In no cases were the caudal rami in _M. pacifica or the Indian Arm specimens ob-served to be shorter than the anal segment. This agrees with the measurements on the Indian Arm specimens (Shan, 1962 Table 23). The urosomal segments including the caudal rami in the female M. pacifica from Japan were reported by Tanaka (1963) as being in propor-tional lengths of 42:23:15:20=100. These same segments in M. pacif ica in the present study, based on sample means (Table 1) are found to be 40:25:15:20=100, while the female M. lucens from the Bay of Fundy are in proportional lengths of 41:23:18:18=100. The proportional lengths in the Indian Arm specimens were found to be identical to M. pacif ica in the present study. Tanaka also reported proportional lengths in the male _M. pacif ica urosome and caudal rami as 15:18:17:14:19=100. The male proportional lengths in this study are 12:19:18:18:13:20=100 for M. paci f ica, 13:19:18:19:12:19=100 for the Indian Arm specimens and for M. lucens 13:19:18:18:14:18=100. The proportional lengths in the present study show the caudal rami to be proportionately longer in M. pacifica and the Indian Arm specimens than in lucens for males and - 52 -females while the length of the anal segment in the females is propor-tionately longer in _M. lucens. The anal segment in the male M. lucens shows i t to be proportionately longer than for M. pacifica and the Indian Arm specimens but is equal to the length of the anal segment when compared with H. pacifica from Japan. Although Tanaka's results are most similar to the females in the present study, his results for the males also demonstrate the longer caudal rami length in respect to the length of the anal segment. His proportional length for the f i r s t urosomal segment in the males and females of M. pacif ica from Japan is longer than for the specimens from Indian Arm. He does not, however, describe where the measurements were taken on the segments nor does he give the sample size on which he based his results. The urosome segments, i t should be pointed out, may vary in proportional lengths within species due to their telescoping ab i l i ty . Block diagrams of the females from the three populations in the present study (Fig. 17) were drawn to scale using the mean of each body measurement. _M. pacif ica is clearly the largest of the three popula-tions in prosome and urosome length. M. lucens is shown as having a longer mean prosome but shorter urosome than for the Indian Arm speci-mens. The Indian Arm specimens display a longer mean second urosomal segment and narrower but longer caudal rami than are found on _M. lucens. The length of the caudal setae on the female Indian Arm specimen (Shan, 1962 p i . V111-I; p i . IX-1 to 3) is not in agreement with the present study. Shan i l lustrates the innermost seta as being the longest while the present study describes the longest as being adjacent to the innermost seta on each caudal ramus (Fig. 1-4). The seta length as i l lustrated in the present study is supported by other authors - 53 -FIGURE 17. Block diagrams drawn to scale of female body measurements. The length of each block represents the mean for that segment taken from Table 1. A- Prosome B- Genital segment C- Urosome segment two D- Anal segment E- Caudal ramus - 53a -jVL. p a c i f i c a M. luceng I n d i a n Arm Specimen nfb LTTJ - 54 -(Tanaka, 1963; Mori, 1964). The setae length for M. lucens (Sars, 1903 p i . LXXVII) is arranged the same as M. pacif ica and the Indian Arm specimens and supported by the present study. This arrangement is the same for the males as well as the females. The lengths of the setae on the male from Indian Arm (Shan, 1962 p i . VI11-3) agrees with the present study. Most drawings by Tanaka (1963) agree with the present study except for the male P5 of_M. pacifica (Tanaka, 1963 Fig. 159-e). He described the male P5 by stating "...the spineform process", (macroprocess), "on the antipenultimate segment of the right leg is much longer than the distal segment of the same leg." This statement does not agree with the present study because the macroprocess on the P5 of _M. pacif ica was never found to be longer than the distal segment. His drawing of the P5 agrees with his statement but the drawing appears to be contorted, especially the three segments P5M3, P5M4 and P5M5. Tanaka does not show any segmentation between the P5M4 and P5M5 in his drawing. The twisted leg (P5M) l ikely contributed to having the macroprocess appear longer than the distal segment when examined under a microscope. The P5 of al l M. pacifica males in the present study were found to be twisted making accurate measurements and assessment of their segment lengths d i f f i c u l t . Tanaka may have used the drawing of a specimen which had a twisted leg for his macroprocess to distal segment length comparison. Unfortunately, I did not have the opportunity to compare specimens of Metridia from Japan with those from Station P, Indian Arm or the Bay of Fundy. I believe, however, from the l i terature (Tanaka, 1963 Fig. 159-d; Mori, 1964 p i . 34 2-5) that M. pacif ica and possibly the smaller population also found in Indian Arm, are resident in Japanese waters. The male P5 was examined in the present study for the three - 55 -populations with a detailed look at the segment P5O4. I l lustrations of the P5O4 and adjacent Segments for M. lucens (Fig. 18-A), the Indian Arm specimens (Fig. 18-3) and JM. pacifica (Fig. 18-C) show a f lexible seta (a) attached near the base of the microprocess (b). The seta is smaller in structure than the microprocess. A spine (c), shorter than the microprocess and f lexible seta was observed near the distal edge of the P5O3. Two i l lustrat ions of the P5 of _M. lucens (Giesbrecht, 1892 p i . 33-22; Sars, 1903 p i . LXXVII) show only the microprocess on the P5O4 as the small seta is absent. Brodsky (1950) used Sars' drawing of the P5 for species identif ication and suggested the one spine (microprocess) on the P5O4 as being characteristic of _M. lucens. Brodsky in his description of 14. pacifica mentions that i t has two inward directed spines on the inner side of the l e f t leg. One spine on the P5O4 and another on the P5O3 and because of these spines claimed a dist inct difference in structure of the P5 between 14. lucens and M. pacif ica. The male P5 of _M. pacifica (Brodsky, 1950 Fig. 201) i l -lustrates the two spines each extending from a different segment as he described in the text and shows them as being of the same nature. Von Vaupel-Klein (1970) disagrees with Brodsky's i l lustrat ion and descrip-tion of these spines by stating that the two spines are not of the same nature and that they originate from the same segment. An i l lustrat ion of the P5O4 and adjacent segments of H. pacifica (von Vaupel-Klein, 1970 Fig. 13-b, c) shows the structure and location of the seta, microprocess and small spine to be as found in the present study. He refers to the "two spines" on the P5O4 as " . . . one being a true spine, projecting from the segment, the other being a spineform projection of the segment." With evidence of the "true spine" (seta) and "spineform projection" (microprocess) being on the P5O4, von - 56 -FIGURE 18. Segmentation of the male P5O Metridia specimens from Indian (C) showing the structure and (a), microprocess (b) and magnification. for Metri di a lucens (A), the Arm (B) and Metridia pacif ica location of the f lexible seta small spine (c). 500 X - 57 -Vaupel-Klein distinguished H. pacifica from _M. lucens based on the presence of the single spine in the drawings of the P5 of M. lucens (Sars, 1903; Giesbrecht, 1892) and on the presence of the two spines in M. pacif ica (Brodsky, 1950; von Vaupel-Klein, 1970). Damkaer (1964) examined the male Metridia from Dabob Bay near Seattle, Washington and in the Pacif ic Ocean near the Strait of Juan de Fuca and found segment P5O4 to have "two spines". He also examined some male M. lucens from the Norwegian coast and found them to have two spines. Damkaer states, "In some preparations the two spines were d i f f i c u l t to distinguish, so previous investigators could have missed one spine." The present study fu l ly agrees with this statement because examination of the P5O4 of _M. lucens, _M. pacif ica and the Indian Arm specimens occasionally showed only one spine. When this occurred the section was examined under a higher magnification and the f lexible seta was most often observed lying alongside the microprocess, or bent so that i t extended over one of the adjacent segments making i t d i f f i c u l t to detect. Some observations did not reveal the seta, even with high magnification, but there is a possibi l i ty of i t being broken off. It is conceivable that the seta could have been overlooked in M. lucens by Giesbrecht and Sars which led to the in i t i a l "one spine" characteristic of M. lucens and the "two spine" characteristic of M. pacifica by Brodsky. The P5 of male M. lucens from the North Sea were examined in the present study and the microprocess and f lexible seta were found to be present in all cases. After observing the "two spines" on the specimens from Dabob Bay, Damkaer considered jM. lucens and H. pacif ica to be synonymous. He also based his decision on the macroprocess to distal segment length com-parison by Tanaka and suggested that Tanaka's comparison was about the same as shown by Giesbrecht (1892) for M. lucens (= M. hibernica). - 58 -It seems that Damkaer did not realize that the drawing of the P5M (Tanaka, 1963 Fig. 159-e) is contorted. Shortly following the publica-tion (von Vaupel-Klein, 1970) Damkaer sent a photograph of the male P5 of _M. lucens and another of the Metridia specimen from Dabob Bay, which was believed by some to be M. pacif ica, to von Vaupel-Klein which showed the microprocess and seta on the P5O4 in both photographs. This convinced von Vaupel-Klein that H. lucens and _M« pacifica were one species, v iz . _M. lucens (Damkaer pers. comm.). An examination of several specimens from Dabob Bay in the present study found them to be synonymous with the Indian Arm specimens and different from_M. pacif ica and M_. lucens. It is understandable that the specimens from Dabob Bay were referred to as _M. lucens by Damkaer due to the number of spines on the male P5. When Dabob Bay specimens were compared in the present study with _M« paci f ica, differences were found as shown between _M. pacifica and the Indian Arm specimens. Von Vaupel-Klein gives the range of total length for the adult female as 2.9 - 3.3 mm for specimens from the Northeastern Pacif ic Ocean. His measurements indicate a similar mean length to those ob-served in the present study for M. pacifica from Station P and longer than the coastal specimens found in Indian Arm and Dabob Bay. This suggests that the specimens von Vaupel-Klein examined were most l ike ly M. pacif ica and not the smaller specimens observed by Damkaer from Dabob Bay. Vidal (1971 Fig. 148) i l lustrates the male P5 of JM. pacif ica from the southern part of the Chukchi Sea. He stated "The male of the species i l lustrated in this key differs from _M. pacif ica (lucens?) by the presence of one spineform process on the proximal part of the distal segment of the right f i f t h leg." As previously mentioned, the seta on the P5O4 in certain preparations is d i f f i cu l t to see. This may - 59 -have been also the situation with Vidal for ^ . pacifica as suspected with Giesbrecht and Sars for _M. lucens. Vidal mentions the one spine-form process (microprocess) as being on the proximal part of the distal segment. It is actually on the P5O4 (penultimate segment) and not the distal segment as he claims. The segmentation in the P5 is well docu-mentated by other authors (Brodsky, 1950; Shan, 1962; Tanaka, 1963; von Vaupel-Klein, 1970) and in the present study showing the microprocess on the P5O4. With evidence of the microprocess and seta being found on the male P5O4 in the present study, the description of _M. lucens and Nl. pacif ica (Brodsky, 1950) should be used with caution. This should also apply to the "one spine" distinction of _M. lucens by Giesbrecht and Sars. The presence or absence of the seta should be especially avoided as a mor-phological characterist ic. Brodsky (1950 Fig. 201) also i l lustrates two P5 for the female M. pacif ica, but one P5 has been erroneously labelled as S^  ( f i r s t swimming leg). This error may have been made during the translation from Russian as the same i l lustrat ion is cor-rectly labelled in an earl ier paper (Brodsky, 1948 Fig. XIV-7). The structure of the P5O4 and adjacent segments for M. lucens, M. pacif ica and the Indian Arm specimens (Fig. 18-A, B, C) shows them to be similar even though the P5O for M. lucens (A) is a l e f t leg while the P5O from the Indian Arm specimens (B) and _M. pacif ica (C) are right legs. There appears to be a difference in the inner margin of the corresponding segments between the populations, especially the P5O3. These differences are not confirmed in the present study due to the l imitation of resolution in the l ight microscope. The structure of these segments would best be i l lustrated for confirmation at the magnification and c lar i ty obtainable by scanning electron microscopy. The structure of the female P5 for M. pacifica has been described - 60 -as having either three or four segments (Brodsky, 1950; Shan 1962; Vidal 1971) and supported in the present study. Other authors (Mori, 1964, M. lucens?; Tanaka, 1963) show the P5 with four segments but Tanaka states that in some specimens, fusion is incomplete in the two distal segments. Mori suggests that there are several variations of the structure of the P5 according to the 'stage of maturity 1. In the present study, variation was found in the structure of the female P5 for al l three populations. The specimens from Indian Arm were found with three basic variations of the P5 (Fig. 19-a, b, c). The P5 most frequently observed had four segments (Fig. 19-b) which does not appear to be as ful ly developed as P5 (c). The P5 with three segments (Fig. 19-a) is the smallest of the three legs with (b) being the intermediate size and (c) the largest. I l lustration of the female P5 of _M. pacif ica from Japan (Tanaka, 1963 Fig. 159-C; Mori, 1964 p i . 34-3, M_. lucens?) appear to be more developed than the Indian Arm speci-men (Fig. 19-b) but less developed than (c). The P5 of M. lucens has been reported as having three segments. Giesbrecht, 1892; Sars, 1903). Brodsky (1950) i l lustrates a three seg-mented P5 for M. lucens but also states that there is a defined fourth segment in specimens from the Atlantic coast of America. Three basic variations of the P5 were also found for N[. lucens (Fig. 19-d, e, f ) . The P5 most frequently observed for N[. lucens (Fig. 19-d) carries a spine at the outer distal end of the third segment. The inner and outer margin of this segment were found to be relat ively parallel over their entire length. The next most frequently observed P5 in M. lucens (Fig. 19-e) had two spines. One on the third segment which appears to be sl ightly closer to the proximal end of the segment than the spine for P5 (d). The second spine was at the outside base of the shortest terminal seta - 61 -FIGURE 19. Variations in the structure of the female P5 of the Metridia specimens from Indian Arm (a, b, c) and Metridia lucens (d, e, f ) . - 61a -- 62 -on the fourth segment. This spine was found to be of variable lengths in relation to the size of the distal segment. The third segment was no longer parallel as the inner margin widened near the proximal end and the outer margin angled towards the distal segment from the loca-tion of the spine. The P5 observed the least number of times (Fig. 19-f) has three spines. Two spines were located about the same as the spines for P5 (e) with the additional spine found on the distal outer corner of the second segment. The shape of the third segment was similar to P5 (e) in respect to the outer margin but the inner margin was shaped l ike a bent elbow with the narrowest section at the middle of the segment. This shape was also observed to be similar in the Indian Arm specimens (Fig. 19-c). Observations on the P5 of the Indian Arm specimens at no time revealed a spine located on the fourth segment at the base of the seta. o The i l lustrat ion of the female P 5 (Mori, 1964 p i . 34-3, M. lucens?) shows variation between the structure of the two P5 on the same specimen. His drawing shows the distal segment of the P5 on the le f t leg as having four setae while only three are found on the distal segment on the right leg. This arrangement was also observed on some of the specimens in the present study. Variations of segmentation in the female P5 has also been shown on specimens from the Chukchi Sea (Vidal, 1971). The lateral profi le of one of these specimens (Vidal, Fig. 142) shows i t to be most l ike _M. pacif ica. One drawing of the P5 (Vidal, Fig. 143) has three segments while another has four segments (Vidal, Fig. 144). Variations of the female P5 within species was also found in the present study by polarized light microscopy (Fig. 20). The P5 from mature M. lucens (Fig. 21-a, b, c) and M. pacifica (Fig. 20-d, e, f) - 63 -FIGURE 20. Polarized l ight microscopy of the female f i f t h legs of Metridia lucens (a, b, c) and Metridia pacifica (d, e, f) showing variation in segmentation and birefringent musculature within each species. - 63a -- 64 -were photographed to show differences in musculature as well as segmen-tation within each species. The birefringent musculature in the photo-graphs is exposed by polarized l ight as either l ight or dark strands (Swann and Mitchison, 1950). This form of observation is possible only i f the cutic le of the object being photographed is transparent and best i f i t is orientated at an angle of 45 degrees to the polarized l ight. The photograph of the P5 of M. lucens (Fig. 20-a) shows both legs as being three segmented with the musculature attached near the proxi-mal end of the distal segment. The photograph of another P5 (Fig. 20-b) shows two legs from the same specimen as being different in musculature as well as segmentation. The P5 on the l e f t in this picture is three segmented with no musculature in the distal segment. The l ight band on the right side of the distal segment results from the thickness of the cuticle at the edge and is not musculature. The P5 on the right in this picture appears to have a small l ine indicating a fourth segment and musculature transversing this segmentation l ine from the third to the fourth segment. The musculature in the distal segment of some specimens appeared to be attached at one end to the base of the terminal setae. This would allow for manipulation of the setae but i f this manipulation was for an important behavorial function, one would expect i t to be evident in all specimens. Some specimens show no musculature in the distal segment, such as was mentioned for the ad-joining P5 (Fig. 20-b), which may suggest that the female P5 is not highly functional. The third photograph in this series (Fig. 20-c) shows a definite fourth segment in the P5 of this _M. lucens specimen. The musculature is also clearly defined as having one end attached to the base of the small distal segment and the other end attached near the proximal end of the third segment. - 65 -Photographs of the P5 of M. pacifica i l lustrate one P5 (Fig. 20-d) as being three segmented with no musculature in the distal segment. Another picture (Fig. 20-e) shows musculature in the distal segment and a possible slight l ine indicating segmentation between the third and fourth segment. The last picture (Fig. 20-f) i l lustrates the P5 as having a defined fourth segment but the c lar i ty of the photograph does not permit an observation of any musculature in the segment. The variation in segmentation on the P5 within each species is evident when the photographs of M. lucens (Fig. 20-a and c) are compared. The same holds true for M. pacif ica i f photographs (Fig. 20-d and f) are com-pared. Al l female specimens selected in the present study were identified as being in the final copepodid and reproductive stage by the characteristic shape of the genital segment (Fig. 1-3). The bulge on the ventral surface, at the genital pores, is not present in premature stages. I do not agree with the suggestion (Mori, 1964) that the variation of the P5 indicates degrees of maturity of the final cope-podid stage. I do agree with the suggestion that the variation of the P5 in Metridia may be the result of i t being so small and l ikely not being a functional appendage, (Frost pers. comm.). Three different states of maturity of the Metridia specimens from Indian Arm were described according to the development of the ovary, oviducal diverticula and eggs, (Shan, 1962). Shan mentions that the P5 with only three segments was observed more frequently on specimens in which the oviducal diverticula was not v is ib le. He also stated that the four segmented P5 was found more frequently on specimens in which the oviducal diverticula and eggs were in an advanced stage of develop-ment. It is conceivable, as Shan has stated, that female Metridia may be found at various stages of maturity in the adult stage in respect to - 66 -the development of their eggs, ovary and oviducal diverticula. The variation in the structure of the P5 in the adult, however, should have no bearing upon the stage of maturity of the eggs and reproductive organs. Changes of segmentation in the copepod exoskeleton occur only as the animal advances from one copepodid stage to another. The adult form is the final and reproductive stage and whatever segmentation forms the exoskeleton when i t reaches this stage, will never change. This applies to the adult skeletal structure of the P5 so to suggest that variation in structure of the P5 may be due to changes of maturity within the adult stage, is not acceptable. It must have been coinci -dental than Shan found the four segmented P5 most often on specimens which were reproductively advanced. The P5 was not observed in the present study according to maturity of the reproductive organs as described by Shan. Segmentation of the P5 should be avoided as a diagnostic feature for identif ication of the three populations in this study. Errors in identif ication could be made within a species i f i t is subdivided according to the P5 segment structure. The evidence of structural differences in the P5 of M. lucens (Fig. 20-a and c) must stress the caution of using the female P5 of this species for morphological characterization because these two legs, as i l lustrated, could con-ceivably be identif ied as being from different species. Shan (1962) mentions the length of the terminal setae on the P5 of his Indian Arm specimens to be of near equal length on three segmented legs. For the legs having four segments he states that the setae de-crease in length from the inner margin towards the outer margin. Brodsky (1950) characterizes M. pacifica by the relative length of the brist les (setae) on the female P5 by saying they are almost equally long. For the present study the setae in the Indian Arm specimens and - 67 -M. pacifica were observed to be of different lengths, decreasing to-wards their outer margin for three and four segmented legs. The inner-most seta was always observed longer than the other two and at no time were the setae observed to be of equal length as i l lustrated by Brodsky (1950, Fig. 201) on the P 5 which is mislabelled. The terminal setae on the female P5 of H. lucens were found in the present study to be as described by Brodsky (1950). The innermost seta was clearly proportionately longer than the other two (Fig. 10). This distinguishing characteristic between _M. lucens and M. pacifica (Brodsky, 1950) is supported by the present study but i t should be noted that the proportional lengths of the setae for the Indian Arm specimens were found to be similar to M. pacif ica. _M. lucens in the Bay of Fundy and the Metridia population in Indian Arm are geographically isolated but because of their similarity in morphology they may have originated from the same population. What caused the division of one population is speculation but the likeness of the two populations suggests that i f this did occur i t may have been recently in terms of evolutionary time, perhaps since the last glacial age, 15,000 to 20,000 years ago. During this glacial period the amount of ice on the land was more than double its present volume. Ice covered much of northern Europe and the northern half of North America and the level of the oceans was much lower than i t is today. Alaska was firmly connected with the U.S.S.R. across the Bering Stra i t . A form of Metridia similar to _M. lucens and the Indian Arm specimens may have existed in either the Atlantic or the Pacific at that time. It may have moved into the Pacific or vice versa through the Bering Strait when Asia and North America were no longer connected due to the rise in the ocean level when the ice melted. The Metridia form may have then began to evolve - 68 -in two directions because of the difference in environmental conditions between the Atlantic and Pac i f ic . Each population, as i t exists today, does not appear to have evolved enough in its own direction to constitute easily distinguish-able differences in morphology from the other populations. There was not one strucure such as a seta, spine or segment that was found to be in addition to or located differently on any of the three populations in this study. Such a structure would have provided a clear, v is ib le means for specific identif icat ion. The use of measurements on segments may be looked upon by some individuals as a questionable means for separating species. When species are morphologically similar, however, the use of segment measurements may be a major and perhaps the only means of identif icat ion. Future morphological comparisons between the populations in the present study should possibly involve the collection of specimens in intervals of every 20 kilometers from the coast to Station P. Vari-ations may be found in the specimens because of differences in water conditions such as turbidity, sa l in i ty, temperature and food avai l -ab i l i ty . Vertical profiles of specimen distribution at these locations may also be informative. Another suggestion, for future consideration, is to rear Metridia in water of different temperatures to check for any effect on growth. Scanning electron microscopy could be used to find possible differences in physical structure not v is ible under the l ight microscope. Metridia are known for their bioluminescent capabil it ies so an examination of the excretory pores used for bioluminescence may reveal them to vary between populations in respect to shape, arrange-ment or location. Interbreeding has been used for separating Atlantic and Pacif ic populations of Acartia clausi (Carri l lo and Mi l ler, 1974). Laboratory - 69 -experiments resulted in the two interbreeding populations not being capable of producing viable offspring. Carr i l lo and Mil ler suggest that the morphologically similar populations of A. clausi had perhaps diverged enough to become reproductively isolated. This concept, a l -though not attempted in the present study, could possibly apply to M. lucens and the Indian Arm specimens. - 70 -SUMMARY Statist ical analyses show the slopes of the regression lines as not being s ignif icantly different for the majority of measurements between the three populations. Significance between the populations is best shown by the analysis of covariance to determine the equality of their adjusted group means. These tests on the means show differences in the females between _M. pacif ica and H. lucens, _M. lucens and the Indian Arm specimens while only two measurements were found to be s ignif icantly different between _M. pacif ica and the Indian Arm speci-mens. The same tests on the males indicated a difference between M. pacif ica and _M. lucens and also between H. pacif ica and the Indian Arm specimens. The regression plots selected of the various measurements show dist inct scatter diagrams for each population with different amounts of overlap. Total length and the length of the second urosomal segment in the females produced the best separation of the scatter diagrams when these measurements were regressed against prosome length. The use of the P5 in the females as a distinguishing morphological feature between the three populations in this study, should be avoided as much var iabi l i ty was found in its structure within the same popula-tion. The P5 of the males, previously used as a distinguishing feature between M. pacif ica and _M. lucens based on the number of spines on segment P5O4, should no longer be used in the same manner to separate these two species. An examination of the male P5 showed each of the three populations to have a similar small f lexible seta and micro-process on segment P5O4. The structure and location of the micro-process and f lexible seta on all three populations suggests that the presence or absence of these features should not be used for species identif icat ion. - 71 -The females may be distinguished by the lateral profi le of the cephalosome; depth of the genital segment; length of the prosome, second urosomal segment, anal segment and caudal rami; width of the anal segment; length to width ratio of the caudal rami and length of the terminal setae on the P5. The males, although similar in size for a l l three populations are best distinguished s ta t i s t i ca l l y on the lengths of urosomal segments three and four, caudal rami length and anal segment length. The data as presented in this study show the Atlantic population to be different than the two populations in the Paci f ic. The Atlantic population is identified as Metridia lucens and the large Pacif ic specimen from Station P most closely f i t s the description of Metridia  pacifica by Brodsky (1950). The smaller Pacific specimens, referred to in the present study as those from Indian Arm, most closely resembles M. lucens in size but differs in accordance to the lengths of certain body segments. The Indian Arm specimens, found abundantly in the coastal waters of British Columbia, possibly may be found also in the mid Pacif ic and could be the population described as the southern small form (Gelatin, 1975). - 72 -LITERATURE CITED Beklemishev, K.V. 1969. Ecology and Biogeography of the Pelagial (Russian), Nauka, Moscow. Boeck, A. 1864. Oversigt over de ved Norges Kyster iagttagne Copepoder henhorende t i l Calanidernes, Cyclopidernes og Harpactidernes Familier. (Norwegian) Vid. Selsk. Forh. Christiania, p. 238. Brady, G.S. and D. Robertson, 1873. Contribution to the Study of the Entomostraca. VIII. On Marine Copepoda Taken in the West of Ireland. Ann. Mag. Nat. Hist., 12 (4). Brady, G.S. 1883. Report on the Copepoda by H.M.S. Challenger During the Years 1873-1876. Challenger Exp. Zool. Vol. 8 part 23. Brodsky, K.A. 1948. Free-Living Copepoda of the Sea of Japan. (Russian) Izv. t ik . naochno-issled. Inst. ryb. Khoz. Okean. 26:57-59, 96, 112. p i . XIV. 1950. Calanoida of the Far Eastern Seas and Polar Basin of the U.S.S.R. Opredeliteli Faune SSSR Zool. Inst. Acad. Nauk. SSSR 35:441p. (Trans, from Russian by Israel Program for Sci. Transl., Jerusalem, No. TT-67-51200, 1967. 440p.) Cameron, F.E. 1957. Some Factors Influencing the Distribution of Pelagic Copepods in the Queen Charlotte Islands Area. J . Fish. Res. Bd. Can., 14(2):165-202. Campbell, M.H. 1929. Some Free-Swimming Copepods of the Vancouver Island Region. Trans. Roy. Soc. Can., 23:303-332. Carr i l lo , E.B.G. and C.B. Mi l ler, 1974. Failure of Interbreeding between Atlantic and Pacif ic Populations of the Marine Calanoid Copepod Acartia clausi Giesbrecht. Limnol. Oceanogr. 19(3): 452-458. - 73 -Damkaer, D.M. 1964. Vertical Distributions of Copepoda in Dabob Bay, December 1960. M.Sc. Thesis, Univ. Wash. Davis, C.C. 1949. The Pelagic Copepoda of the Northeastern Pacif ic Ocean. Univ. Wash. Publ. B io l . , 14:1-118. Esterly, CO. 1924. The Free-Swimming copepoda of San Francisco Bay. Univ. Ca l i f . Publ. Zool., 26(5):96, 97. Fleminger, A. 1967. Taxonomy, Distribution and Polymorphism in the Labidocera jol lae group with remarks on evolution within the group (Copepoda:Calanoida). Proc. U.S. Nat. Mus. 120 (3567):1-61. Frost, B.W. 1971. Taxonomic Status of Calanus finmarchicus and C_. glacial is (Copepoda), with special reference to adult males. J . Fish. Res. Bd. Can. 28:23-30. 1974. Calanus marshal!ae, A New Species of Calanoid Copepod Closely A l l ied to the Sibling Species £ . finmarchicus and C_. glacial is. Mar. Biol . 26:77-99. Gardner, G.A. 1977. Analysis of Zooplankton Population Fluctuations in the Strait of Georgia, Brit ish Columbia. J . Fish. Res. Bd. Can. 34:1196-1206. Gelatin, Y.V. 1975. Distribution of Copepod Metridia pacifica in Northwest Pacif ic Ocean in Relation to Water Temperature. Inst. Mar. B io l . , Far East Scient i f ic Center, Acd. Sci. U.S.S.R. s Trans, from Ekologiya 3:68-72. Giesbrecht, W. 1892. Systematik und Faunistik der pelagischen Cope-poden des Golfes von Neapel und der angrezenden Meeresabschnitte. Fauna Flora Golfes Neapel Monogr. 19:1-831. 1895. Die pelagischen Copepoden. Rep. Dredg Oper. West Coast Centr. Amer. in Charge of Alexander Agassiz, Carried on by the U.S. Fish Commission Steamer "Albatros" During 1891. Bul l . Mus. Comp. Zool., Harvard Co l l . , 25(12). - 74 -Legare, J.E.H. 1957. The Qualitative and Quantitative Distribution of Plankton in the Strait of Georgia in Relation to certain Oceano-graphic. Lucas, C.E., R.E. Glover and A. Hardy, 1973. Continuous Plankton Records: A Plankton Atlas of the North Atlantic and the North Sea. By the Oceanographic Laboratory, Edinburg. Bul l , of Mar. Ecology. Publ. Inst. Mar. Envir. Res., Plymouth, p. 128. Mori, T. 1964. The Pelagic Copepoda from the Neighbouring Waters of Japan. Soyo Company No. 1-17, 2-Chome, Ohkayama, Meguro-ku, Tokyo, Japan. Published post humously 2nd ed.; original private publication, 1937. Park, T.S. 1968. Calanoid Copepods from the Central North Pacific Ocean. Fishery Bull. Fish Wildl. Serv. U.S. 66:527-572. Roff, J.C. 1972. Aspects of the Reproductive Biology of the Plankton Copepod Limnocalanus macrurus Sars, 1863. Crustaceana 22:156-160. Sars, G.O. 1903. An Account of the Crustacea of Norway. Vol. 4. Copepoda Calanoida (Pts I,II), 28pp. Bergen Museum, Bergen. Sewell, S. 1932. The Copepoda of Indian Seas. -Mem. Indian Mus. Vol. 10. Shan, Kuo-Cheng 1962. Systematic and Ecological Studies on Copepoda in Indian Arm, British Columbia. M.Sc. Thesis, Univ. Brit ish Colum-bia. Swann, M.M. and J.M. Mitchison, 1950. Refinements in Polarized Light Microscopy. J . Expt. B io l . 27:226-237. Tanaka, 0. 1963. The Pelagic Copepods of the Izu Region, Middle Japan Systematic Account IX pp. 15-22. Reprinted from Publ. Seto Mar. Biol. Lab. IX (1). - 75 -Vidal, J . 1971. Taxonomic Guides to Arctic Zooplankton IV. Key to the Calanoid Copepods of the Central Arctic Ocean. Tech. Rep. No. 5. Univ. South. Ca l i f . , Dept. Biol . Sci. Vinogradov, M.E. 1968. Vertical Distribution of the Ocean Zooplank-ton. Acad. Sci. U.S.S.R., Inst. Oceanog. Trans, from Russian by Israel Prog. Sci . Trans., Jersulem, 1970. Dist. by N.T.I.S. TT 69-59015. von Vaupel-Klein, J.C. 1970. Notes on a Small Collection of Calanoid Copepods from the Northeastern Pacif ic, Including the Description of a New Species of Undine!la. (Fam. Tharybidae) Zool. Verh. No. 110. Woodhouse, CD. 1971. A Study of the Ecological Relationships and Taxonomic Status of Two Species of the Genus Calanus (Crustacea: Copepoda). Ph.D. Thesis, Univ. Brit ish Columbia 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0094801/manifest

Comment

Related Items