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Some factors affecting distribution and productivity in the estuarine amphipod Anisogammarus pugettensis Chang, B. D. 1975

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SOME FACTORS AFFECTING DISTRIBUTION AND PRODUCTIVITY IN THE ESTUARINE AMPHIPOD ANISOGAMMARUS PUGETTENSIS •  '  by BLYTHE DAMON CHANG  B.Sc, University of B r i t i s h Columbia, 1972 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE  \  i  in the Department •.  of Zoology  We accept t h i s thesis as conforming to the required standard  THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1975  In p r e s e n t i n g  t h i s t h e s i s in p a r t i a l  f u l f i l m e n t o f the  requirements f o r  an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree the L i b r a r y s h a l l make i t f r e e l y  a v a i l a b l e f o r r e f e r e n c e and  I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e f o r s c h o l a r l y purposes may by h i s r e p r e s e n t a t i v e s .  written  gain  permission.  Department of  ~£oO  C 0 6 /  The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada  shall  not  thesis  Department or  I t i s understood that c o p y i n g o r  of t h i s t h e s i s f o r f i n a n c i a l  study.  copying o f t h i s  be g r a n t e d by the Head of my  that  publication  be a l l o w e d w i t h o u t  my  i  ABSTRACT Factors affecting the d i s t r i b u t i o n and productivity of the benthic estuarine amphipod Anisogammarus pugettensis (Dana) were examined.  Data  were obtained from f i e l d samples taken from Crescent Beach, B r i t i s h Columbia, between May  1973  and September 1974.  Tolerances to selected  physical factors, growth rates, oxygen uptake, and assimilation e f f i ciency were measured i n the laboratory.  This species i s present  appears to reproduce throughout the year at Crescent Beach. bution i s affected by:  and  Distri-  avaoidance of temperature extremes and desicca-  tion, which r e s t r i c t the species to the middle i n t e r t i d a l zone and deeper at low tide; avoidance of anoxic and low oxygen waters; s a l i n i t y intolerances, which r e s t r i c t the species to outer estuarine areas; and food a v a i l a b i l i t y .  Productivity within inhabited areas i s  affected mainly by temperature, and food quantity and q u a l i t y . Productivity w i l l be greatest i n warm months.  Growth rates, growth  e f f i c i e n c i e s , and reproductive a b i l i t y are high compared to values reported for other species.  A. pugettensis i s an omnivore, capable of  eating a wide v a r i e t y of foods. i s an important  These data indicate that this species  consumer organism i n the estuarine environment.  The  wide tolerances to physical factors, broad d i e t , and high productivity w i l l make i t suitable for mariculture impoundments, i f i t can be shown that the cultured f i s h w i l l show high growth rates when feeding on these amphipods.  ii  TABLE OF CONTENTS  Page ABSTRACT  .  TABLE OF CONTENTS LIST OF TABLES  ..  ACKNOWLEDGEMENTS  II. III.  ...... i i  ....  v  LIST OF FIGURES  I.  ....  ...  .•  ;1  DESCRIPTION OF. A. PUGETTENSIS  3  FIELD STUDIES A.  Description of C o l l e c t i n g S i t e  B.  Methods  •  7 7 10  1.  C o l l e c t i o n of Samples  10  2.  Brood Size vs. Female Size Relationship  11  Results  11  1.  Length-Frequency Data for.Samples  2.  Relative Numbers of Males, Females,, and  12  Reproductive Females  19  3.  Size of Adults  21  4.  Relationship between Brood Size add Female Size  21  LABORATORY . STUDIES A.  vi  viii  INTRODUCTION  C.  IV.  i  26  Methods  26  1.  Maintenance of Amphipods  26  2.  Length-Weight Relationships  26  3.  Tolerance Experiments  . ...  27  iii  Page 4.  Effect  of Temperature on Incubation Time  28  5.  E f f e c t s of Temperature and S a l i n i t y on Growth. ..  29  6.  E f f e c t s of Temperature, S a l i n i t y , and Oxygen Levels on Oxygen Consumption  29  7.  Feeding Experiments  31  8.  Growth E f f i c i e n c i e s  34 .  B.. Results  V.  VI. VII.  36  1.  Length-Weight Relationships.  36  2.  Tolerance Experiments  3.  Effectoof Temperature on Incubation Time  4.  E f f e c t s of Temperature and S a l i n i t y on.Growth  5.  Effects of Temperature, Salinity.,, and Oxygen.  .......  36 42 ..  42  Levels on Oxygen. Consumption.  45  6.  Feeding Experiments  50  7.  Growth E f f i c i e n c i e s  61  DISCUSSION  76  A.  Factors Affecting D i s t r i b u t i o n  76  B.  Factors Affecting Productivity........  79  C.  Productivity of A. pugettensis .  84  D.  Importance to Mariculture  92  LITERATURE CITED APPENDICES  95 '  A.  Data.for individual f i e l d samples  B.  Means and Sample.standard deviations for length vs.  99 99  age data of males and females at d i f f e r e n t temperatures and s a l i n i t i e s  i'0-5  iv  Oxygen uptake of individual animals at different acclimation and test  temperatures  V  LIST OF TABLES Page I.  Percentages of. males, t o t a l females, and reproductive females among adults i n f i e l d .samples  II. III.  ...................  Survival at high temperatures after 24 h exposure  41  Survival at high and low s a l i n i t i e s after 24 h exposure  IV.  VII.  .. ..  41  The effect of s a l i n i t y (10° C) on.the.relationship between oxygen uptake per animal and dry.body weight  VI.  41  Survival i n anoxic conditions induced by the addition of sodium s u l f i t e  V.  20  Assimilation e f f i c i e n c i e s of adults  ...  49 64  Assimilation e f f i c i e n c i e s of plant foods by benthic amphipods  86  vi  LIST OF FIGURES Page; 1.  Diagram of adult. A., pugettensis  4  2.  Map of Crescent Beach area  8  3.  Length-frequency data f o r f i e l d samples  4.  Temperature and s a l i n i t y data obtained at sampling  13  times 5.  Size of reproductive females collected at. Crescent Beach  6.  16  ...  .... .......  22  Brood size vs. female size data f o r animals collected at Crescent Beach  24  7.  The relationship between head length and dry. weight  8.  The relationship between dry weight and. ash-rf ree dry weight  9.  ,  37  39  Growth i n head length, at d i f f er ent ..temperatures and salinities  10.  ....  . ....  43  The effect of acclimation and test temperatures on oxygen consumption  46  11.  Oxygen consumption i n decreasing oxygen .levels at 10° C .  51  12.  Growth i n head-length with various foods  53  13.  Egestion rates (mg C/day) at. 20° C  62  14.  Growth i n dry. weight at 10 and 20° C (24%.)'.  66  15.  Growth.rate vs. body weight at .10 and.20° C (24%.)  68  16.  Oxygen uptake vs. body.weight at 10 and 20° C (24%.)  17.  Assimilated rations vs. body weight.at 10 and 20° C  ...............  ...  (24%.) 18.  Net; growth e f f i c i e n c y (K/?) vs. body weight at 10 and 20  70  72  vii  Page °C (24%.)  .  74  viii  ACKNOWLEDGEMENTS I thank Dr. T. R. Parsons for providing supervision and f a c i l i t i e s for t h i s study.  A. B. Norton, D. Kirk, C. L. Tsuyuki, and C. A. Bawden  provided much valuable assistnace.  Amphipod specimens were i d e n t i f i e d  by D. Laubitz and Dr. E. L. Bousfield of the National Museum of Canada, and Dr. C. D. Levings of the P a c i f i c Environment Institute.  The manu-  s c r i p t was c r i t i c a l l y read by Drs. J . R. Stein and A. G. Lewis.  I  was supported by a postgraduate scholarship from the National Research Council of Canada.  I.  INTRODUCTION Amphipods (class Crustacea, subclass Malacostraca,  superorder  Peracarida) are common organisms i n shallow marine environments (Barnard 1969).  On the B r i t i s h Columbia coast, amphipods are often  found i n large numbers.  In the Squamish estuary, amphipods are  extremely abundant i n sedge rhizomes, and are the major food of juvenile salmon and other fishes i n the estuary (Goodman and Vroom 1972;  Levings 1973).  At Bamfield, amphipods are the most important  food for shallow subtidal fishes (B. Leaman, personal communication). Large numbers of amphipods are often found i n polluted waters adjacent to pulp m i l l s (Waldichuk and Bousfield 1962;  Harger and Nassi-  chuk 1974). These observations indicate that amphipods are widely d i s t r i b u t e d , highly productive, and an important part of food webs i n estuarine environments i n B r i t i s h Columbia.  However, there i s a lack of experi-  mental evidence to confirm these observations.  In the present study,  f i e l d samples were taken, and laboratory experiments conducted, i n order to examine factors affecting d i s t r i b u t i o n and productivity i n a benthic estuarine amphipod. Another object of this study was to determine i f a benthic estuarine amphipod would be useful i n salmon mariculture impoundments. If a mariculture impoundment contains an animal that can grow and produce as part of the natural food web,  and which can be eaten by  salmon, then the high costs of adding a r t i f i c i a l f i s h feeds can be l a r g e l y reduced or eliminated (Powers 1973) .  Shallow-water benthic  amphipods may be suitable i n t h i s r o l e for the following reasons: they may n a t u r a l l y occur i n impoundments (Powers 1973) ;  because they  are adapted to an environment characterized by fluctuating conditions,  2  and can exist i n polluted conditions (see above) , they should be able to t o l e r a t e the environmental fluctuations that may occur i n a shallow impoundment (Brown and Parsons 1972); diet (Kinne 1959;  Martin 1966;  ments can be e a s i l y met;  they appear to have a broad  Levings 1973), so their food require-  their often large numbers (see above) i n d i -  cates high productivity '(which i s needed for high f i s h production); and they are an important food for juvenile salmon i n the natural environment  (see above).  These q u a l i t i e s must be confirmed i n any  amphipod species that would be present i n an impoundment i n order to determine the f e a s i b i l i t y of amphipod-salmonid mariculture. The present study examined c e r t a i n aspects of the ecology of Anisogammarus pugettensis (Dana), a common amphipod of the B r i t i s h Columbia coast (Waldichuk and Bousfield 1962).  Data were obtained  concerning factors affecting i t s d i s t r i b u t i o n and productivity, and these findings were related to i t s s u i t a b i l i t y f o r mariculture. The e f f e c t s of selected factors on d i s t r i b u t i o n were determined  from  f i e l d data on abundance, temperature, and s a l i n i t y , laboratory measuremerits of tolerances to certain physical factors, and the a b i l i t y of various foods to support survival and growth.  The effects of selected  factors on productivity were determined from estimates of growth e f f i c i e n c y and reproductive a b i l i t y under various conditions.  Growth  e f f i c i e n c i e s were estimated from laboratory measurements of growth, oxygen uptake, and assimilation e f f i c i e n c y .  Reproductive a b i l i t y  was  estimated from brood sizes and the occurrence of reproductive animals and young i n f i e l d samples, and laboratory measurements of incubation time and growth.  Growth e f f i c i e n c i e s and reproductive a b i l i t y were  compared to data obtained by other authors for amphipods and other aquatic animals.  F i e l d samples were taken from May 1973 to September  3  1974 at Crescent Beach., B r i t i s h Columbia.  II.  DESCRIPTION OF A. PUGETTENSIS Anisogammarus pugettensis (Dana) i s a gammarid amphipod found i n  cold, s l i g h t l y brackish, shallow waters from Alaska to central C a l i f o r n i a (Barnard 1954; 1962).  Light et a l . 1954;  Waldichuk and Bousfield  It occurs at 30 m depth i n polluted waters near a pulp m i l l  near Prince Rupert (Waldichuk and Bousfield 1962) . Adults are diagrammed i n F i g . 1 (see also Barnard 1954). males are usually larger than females. by the size of the gnathopods of oostegites (not shown). and other objects;  Mature  Sexes can be distinguished  ( F i g . 1) and by the presence or absence  Gnathopods are used for grasping food  pereopods are used f o r walking and for c l i n g i n g  to seaweeds or other surfaces; v e n t i l a t i o n of g i l l s .  pleopods are used for swimming and  G i l l s (not shown) are found on the appendages  of pereon segments 2-6.  Oostegites, found on the appendages of  pereon segments 2-5, form the marsupium (brood pou:gh>X)< i n mature females.  Food objects are broken up by the gnathopods and mandibles.  Mandibles have cutting and grinding (molar) surfaces (Barnard 1954). Mating i s similar to that of other gammarid amphipods (see Hynes 1955;  Kinne 1959).  Copulation i n A. pugettensis i s preceded  by a period of precopula;^lasting for from l e s s than 1 day to 7 or more days, i n which the malesholds the female's anterior body segments with h i s gnathopods.  Precopula appears to be i n i t i a t e d by a random  c o l l i s i o n between a male and female.  The female sometimes breaks  away from the male before copulation has taken place; occurs most often early i n the female's molt cycle. follows molting by the female.  t h i s probably  Copulation  The male and female then separate  4  Figure 1.  Diagram of adult A. pugettensis. A, antennae (2 p a i r s ) ; antennae);  (a) male;  AF, accessory flagellum (on 1st  G, gnathopods (2 p a i r s ) ;  M, maxillipeds(1 p a i r ) ; pleopods (3 p a i r s ) ;  (b) female.  HL, head length;  P, pereopods (5 p a i r s ) ;  U, uropods (3 p a i r s ) .  PL,  5  0 1 I 1 mm  6  and the female ovulates, r e s u l t i n g i n a mass of blackish eggs (each ca. 0.4 mm diameter) i n the marsupium.  The female c a r r i e s the embryos u n t i l  just after hatching. During the development of the embryos, females frequently beat their pleopods to v e n t i l a t e the marsupium.  Young are  released over a period of 1-3 days, just before, or a t , the next female molting. Newly released young have b a s i c a l l y the same extermal appearance as adults (except there i s no sexual dimorphism i n gnathopods, and oostegites are absent), with a head length of ca. 0.25 mm. occurs v i a a series of molts.  Growth  Molts are eaten after molting. Although  not measured d i r e c t l y , data from growth studies and the recovery of some molts indicate that 7-10 molts are required to a t t a i n maturity CO.9-1.2 mm head length). Females i n precopulatare sometimes carrying a brood.  Following  the next female molt, any remaining young from t h i s brood are released and copulation occurs, followed by ovulation.  In other cases, females  have a resting period of at least 1 molt cycle between successive broods.  The potential number of broods per female was not measured;  some individuals had 3 broods i n the laboratory, but more may be possible. In the f i e l d and i n laboratory cultures, the amphipods are not e a s i l y seen.  They are usually c l i n g i n g to seaweeds or are under  rocks, s h e l l s , or other objects.  Behavioral observations indicate  an a t t r a c t i o n to objects to which they can c l i n g .  7  III. A.  FIELD STUDIES DESCRIPTION OF COLLECTING SITE Samples were taken on the northwest side of Blackie Spit at  Crescent Beach, B r i t i s h Columbia (49°04'N, 122°53'W;  F i g . 2). This  area i s shallow with extensive mudflats exposed at low t i d e . depth i s ca. 3 m below lower low water.  Maximum  The beach area i s sandy i n  the high i n t e r t i d a l zone, becoming muddy i n the lower zones.  Living  macroflora consists mainly of Zostera marina L. (low on the beach) and Enteromorpha spp. (mostly high on the beach).  Small, shallow,  ephemeral, muddy tidepools (up to ca. 1 m diameter, 20 cm deep) are present i n the middle and lower i n t e r t i d a l zones at low t i d e . These pools usually contain dead strands of Zostera, especially i n winter and spring.  Small cast-up clumps (up to ca. 1 m long of  unattached  seaweeds, mainly dead Zostera and Enteromorpha, occur  throughout  the i n t e r t i d a l zone, especially i n spring and summer.  Clumps of dead Zostera are present at the highest high water l i n e throughout  the year.  Large amounts of an unattached red alga, Chondria  decipiens K y l i n , covered most of the beach from August to early October in 1973 and 1974. A thin coating of benthic diatoms often covers much of the mud surface ( i d e n t i f i e d by D. Kirk as Licomorpha sp.). The i n t e r t i d a l epifauna includes several amphipod species. Arilsogammarus pugettensis (Dana) i s the most common species. include, i n approximate order of abundance:  Others  Allorchestes angustus  Dana, Anisogammarus confervicolus (Stimpson), Atylus c o l l i n g i (Gurjanova) (mainly i n winter), Corophium sp. (mainly i n spring), and Amphitho'e v a l i d a Smith (mainly i n spring) . Harpacticoid copepods are common i n tidepools. Other i n t e r t i d a l epifauna include hermit  8  Figure 2.  Map of Crescent Beach area. Blackie Spit;  *, sampling s i t e on  , high tide l i n e ;  , low tide l i n e .  (Redrawn from map  92 G/2 W, edition 3, Canada Department of Mines and Technical Surveys, 1961).  1  10  crabs  (Pagurus  zonalis  s p . ) , the s n a i l s N a s s a r i u s o b s o l e t u s Say and  ( B r u g i e r e ) , and  Batillaria  the b a r n a c l e Balanu s g l a n d u l a Darwin.  Sculpins  COligocottus maculosus) sometimes occur i n t i d e p o o l s . A. p u g e t t e n s i s i s the o n l y common amphipod i n s u b t i d a l t r a p samples (see methods below).  P r i c k l e b a c k s (Anoplarchus  purpurescens)  are  found  subtidally.  B.  METHODS  1.  C o l l e c t i o n of Samples Monthly samples (May  middle  and  lower  1973-September 1974)  were taken from  the  A. p u g e t t e n s i s  was  i n t e r t i d a l zones a t low t i d e .  c o l l e c t e d from t i d e p o o l s u s i n g s m a l l , fine-mesh  dip nets  d i a m e t e r ) , b u l b p i p e t t e s ( i n n e r diameter  by hand, or by  8 mm),  (6 cm  c o l l e c t i o n of the p l a n t m a t e r i a l t o which the amphipods were a t t a c h e d . D u r i n g the l a t e s p r i n g and were more commonly found Enteromorpha and  e a r l y summer, e s p e c i a l l y i n 1974,  i n s m a l l clumps of seaweeds  Z o s t e r a ) i n the m i d d l e and  lower  (unattached  intertidal  Amphipods were removed by hand or by c o l l e c t i o n of seaweed. 3 hours were spent i n c o l l e c t i n g a sample; times o c c u r r e d when the fewest A few  the l o n g e s t  zones. Up  to  sampling  amphipods were p r e s e n t .  samples were taken from the s h a l l o w s u b t i d a l a r e a i n  A p r i l to J u l y 1974  u s i n g a t r a p c o n s i s t i n g of 2 connected  (each c a . 30 X 20 X 20 cm, s m a l l styrofoam c h i p s and cage was  amphipods  openings  c a . 1.5  one c o n t a i n i n g  the o t h e r c o n t a i n i n g s m a l l s t o n e s ;  b a i t e d w i t h Enteromorpha and  a p i l i n g and allowed  cm),  w i r e cages  Zostera.  The  t r a p was  each tied  to  to r e s t on the bottom a t a depth of ca_. 2 m  below the low i n t e r t i d a l zone. would l e a v e the t r a p as i t was  I t was  sometimes noted .that amphipods  being l i f t e d  to the s u r f a c e .  11  The amphipods and seaweeds from each c o l l e c t i o n were brought to the laboratory i n 2 1 vacuum f l a s k s .  Live individuals of A. pugettensis  were sexed, measured for head length (Fig- 1)> females were checked for the presence of eggs or embryos, and mating pairs were noted. Amphipods were sexed according to the size of the gnathopods (see F i g . 1).  This method i s accurate for large animals, but i s l e s s  r e l i a b l e for the size class i n which the amphipods f i r s t mature (head length 0.9-1.1 mm).  The minimum size of reproductive females  in f i e l d samples was used as an estimate of the minimum size at maturity.  Animals classed as reproductive females were females i n  precopula and females carrying eggs, embryos, or young. When large numbers of A. pugettensis were c o l l e c t e d , only a subsample of 70-140 animals was measured.  2.  Brood Size vs. Female Size Relationship For some samples, some of the ovigerous (bearing eggs or embryos)  females were isolated and either preserved i n formalin or kept a l i v e i n the laboratory u n t i l the young were released.  In the l a t t e r  situ-  ations, i n d i v i d u a l females were kept i n 100-200 ml seawater and provided with excess food (Enteromorpha i n t e s t i n a l i s ) .  The numbers of  eggs, embryos, or young were counted, and the female's head length measured.  C.  RESULTS Quantitative estimates of the population size at Crescent Beach  were not obtained because of the extreme patchiness of d i s t r i b u t i o n (in space and i n time) i n the i n t e r t i d a l zone.  Any population estimates  12  must also include subtidal i n d i v i d u a l s . The numbers of amphipods collected i n each, month depended upon the number of samples taken i n each month, the time spent c o l l e c t i n g each sample (the time was inversely related to the numbers present), and the type of habitat sampled (see below), as well as the numbers a c t u a l l y present.  Because of t h i s , and because only subsamples were  measured when large numbers were c o l l e c t e d , the t o t a l numbers and the numbers of adult males, females, and reproductive females shown i n the r e s u l t s are not i n d i c a t i v e of the actual numbers present i n each month.  For data concerning reproductive females, i n some months  not a l l ovigerous females shown i n the length-frequency data had their broods measured, while i n other months, data were obtained for reproductive females from samples or subsamples not included in the length-frequency data.  1.  Length-Frequency Data for F i e l d Samples The length-frequency data f o r f i e l d samples for May 1973 to  July 1974 are shown i n F i g . 3 (see also Appendix A).  The tempera-  tures and s a l i n i t i e s i n tidepools at sampling times are shown i n F i g . 4 (also Appendix A). Temperatures ranged from 5-24° C, s a l i n i t i e s from 19-27%*  The low temperatures  i n November 1973 to early February  1974 were p a r t l y due to the night sampling times during t h i s period. a.  Late October 1973 to A p r i l 1974  During t h i s period, a l l samples were taken from tidepools containing strands of dead Zostera, from exposed Zostera beds, or from cast-up clumps of seaweeds.  In November, December, and early Feb-  ruary, the r e l a t i v e scarcity of small size classes was probably due  13  Figure 3.  Length-frequency data f o r f i e l d samples.  A l l samples  i n any one month are pooled (see Appendix A).  Indivi-  duals with head lengths less than 0.3 mm are not included.  The largest size class represents individuals  1.7 mm and larger.  Solid bars represent reproductive  females (ovigerous or mating females). in parentheses following which samples were taken;  The numbers  the month are the dates on *, indicates a subsample.  14  MAY 1 3 7 3 ( i n . )  JLTE 1273  1.-182  DO'  £»•  (i,19.28)  W!) 97  GO.  40.  2  20.  20.  0-3 0-5 0-7 0-3 1.1 1.3 1-5 1-7 JXY  1373  0-3 0-S C7 0-9 1-1 1-3 1-5 1-7  AUGUST 1H73 ( 27)  (16,30*)  I.--72  11-246  DO'  BO.  0-3 0-5 0-7 0-9 1.1 1.3 1.5 1-7 SEPTEKSER 1373 (u»)  CCTCE£R 1373 (23*) 11-116  N-79  2  B  0-3 0-5 0-7 0-9 1-1 1-3 1-5 1*7  DECEMBER 1373 (19*)  N 0 V E K 6 E K 1 9 7 3 (22«) GO'  K-105  N-117  DO'  .  60. 40'  40.  200-3 0-5 0-7 0.9 1-1 1-3 1.5 1-7 0-3 0-5 0-7 0-3 1-1 1-3 1.5 1-7 ...  rGAD LD-GfH CKM)  I CAQ LENGTH (KM)  15  FEBRUARY 1374 BO-  (4*.28*)  MARCH 1374  N-154  SO-.  (28»)  a-103  £0.  40-  40.  £0-1  0-3 0-5 0-7 0-9 1-1 1-3 1-S 1.7 0*3 0-S 0-7 0-3 1-1 1-3 l.S i-7 /FR1L  1374  (9.,25«.26.)  MAY  K-260  1374  (8*,27)  N-160  0-3 0-S 0-7 0-9 1-1 1-3 1-S 1-7 0-3 0-S 0-7 0-9 Ll 1-3 1-S 1-7 JLNE: 1374  (4*.18)  JLLY 1374  N-276  EO.  0-3 b-S  0-7  rCAO  0.3  1-1  LEN3TH  1-3 1-S 1-7 (KM)  (9\30«)  N»210  -I  0-3 0-S 0.7 0-3 HEAD LENGTH  CMM)  1-1  L3 l.S  1.7  16  F i g u r e 4.  Temperature and s a l i n i t y d a t a o b t a i n e d a t sampling times.  Each p o i n t r e p r e s e n t s t h e mean of 2 o r more  t i d e p o o l s i n the m i d d l e or lower i n t e r t i d a l  zone.  FIELD TOvFO^TLFES  a  •as. +  +  +  EO-1  ++  ++  •+ + +  u  +  +  +  5.1  M  H  J  1J  1  A  1  S  —| O  H N  h  1  D  J  F  1  1  1  1  M  A  M  J  1S73  b  1  1  J  i  A  1974  FIELD SALINITIES  30.  as.  ++  +  +  +  + SO.  ++  +  2  5-1  H 1 M J J  1  1 A  1 1 (S O N D  1373  1 J  F  1  1  1—H  M  A  M 1374  1 J  J  1 A  1  18  to the reduced v i s i b i l i t y at night;  young that were found were  a c c i d e n t a l l y taken by pipette or were on strands of seaweed that were carried back to the laboratory. A. pugettensis  was abundant i n tidepools i n these months,  and tidepools were also abundant. present throughout t h i s period. 1974.  Reproductive females and young were  No samples were taken i n January  However, reproductive females and young were present i n  December 1973 and February 1974, and adults and young were found i n this area i n January 1973 (D. Kirk, personal communication).  These  data indicate that reproducing adults and young probably occurred i n January 1974. b.  Late A p r i l to July  During t h i s period (both years), tidepools did not contain as much Zostera as i n winter months.  A. pugettensis was also l e s s  abundant i n tidepools; aduMsuwdrje £e's.p1eteLaM»ya scarce, except on July 30, 1973 when tidepools containing Zostera were present.  However,  on some days during t h i s period, few amphipods were found even when tidepools with Zostera were present.  As a r e s u l t , i n May and June  1973, when only tidepool samples were taken, the samples were almost e n t i r e l y composed of young. In July 1973 and May-July 1974, amphipods were also collected i n t e r t i d a l l y from clumps of cast-up seaweeds (Zostera and Enteromorpha), and i n l a t e A p r i l 1974, from exposed Zostera beds i n the low i n t e r t i d a l zone.  Samples from these habitats often contained high d e n s i t i e s of  A. pugettensis including many adults and older j u v e n i l e s . These seaweed clumps were not present i n winter months.  A. pugettensis  was absent from the dead Zostera at the highest high water l i n e at  a l l times of the year. Subtidal samples were taken from a depth of ca_. 2 m below low i n t e r t i d a l zone i n l a t e April-June 1974.  In these samples, large  numbers of A. pugettensis often occurred. adults;  young may  have been present, but were d i f f i c u l t to detect  and remove from the trap. found.  These were predominantly  In some trap samples, few amphipods were  This appeared to be the r e s u l t of removal of the seaweed  b a i t , possibly by grazing amphipods.  On A p r i l 25 and June 4,  large numbers were found subtidally when few were present  1974,  inter-  t i d a l l y (very few i n pools, few clumps of seaweed, present).  If the  d i f f e r e n t types of samples for late A p r i l to July are combined, i t i s seen that adults, including reproductive remales, and young were present throughout t h i s period. c.  August to Early October  During these months (both years) only i n t e r t i d a l samples were taken. absent;  However, seaweed clumps of Zostera and Enteromorpha were tidepools were also scarce, and contained l i t t l e seaweed.  During this period, the e n t i r e beach (except the highest parts) covered with a mat of unattached Chondria.  was  The i n t e r t i d a l samples  taken at t h i s time usually contained few A. pugettensis, and when found, there were few adults (including few reproductive females).  2.  Relative Numbers of Males, Females, and Reproductive The percentages of males, t o t a l females, and  Females  reproductive  females among adults i n f i e l d samples are shown i n Table I.  Male:  female r a t i o s were v a r i a b l e , but usually close to unity. Errors»' i n these values may  be due to the small sample sizes i n some months,  and the incorrect sexing of smaller adults.  Reproductive  females  Table I.  Percentages of Males, Total Females, and Reproductive Females i n Adults i n F i e l d Samples.  No. Adults  % Males  % Total Females  May  11  64  36  9  Jun  3  67  33  33  Jul  88  52  48  22  Aug  8  38  62  13  Sep  5  40  60  0  Oct  24  67  33  13  Nov  49  59  41  29  Dec  56  57  43  9  Feb  49  47  53  45  Mar  17  35  65  59  Apr  148  48  52  34  May  57  61  39  18  Jun  132  55  45  34  Jul  66  67  33  18  Aug  2  0  100  100  Month  % Reproductive Females  1973:  1974:  21  were ca. 50% or more of the t o t a l females i n a l l months i n which at least 10 females were collected;  an exception was December 1973.  Almost a l l non-reproductive females were i n the smallest adult sizes (see Appendix A);  therefore, many of these may have been immature  or i n c o r r e c t l y sexed, r e s u l t i n g i n underestimates of the r a t i o s of reproductive females to t o t a l females.  3.  Size of Adults As shown i n F i g . 5, the minimum, mean, and maximum sizes of  reproductive females changed over the year, being smallest i n July, and largest i n February and March.  S u f f i c i e n t data were not obtained  for August, September, or January.  A similar seasonal size trend  appeared to occur i n mating males, but there was i n s u f f i c i e n t data to confirm t h i s . of 1.2 mm  The smallest mating male c o l l e c t e d had a head length  (June 1974).  The largest individual collected was a 2.1  mm  male (February 1974) .  4.  Relationship between Brood Size and Female Size Brood size vs. female size data for each month are shown i n  F i g . 6.  There was a general increase i n brood size with female s i z e ,  but with much v a r i a b i l i t y . small broods.  Some of the largest females had r e l a t i v e l y  Females collected i n June 1974 had larger broods at a l l  female sizes up to 1.5 mm than i n any other month.  Average brood  sizes per female were calculated for months i n which 8 or more ovigerous females were measured. Mar/74, 72;  Apr/74, 55;  The averages were: May/74, 49;  Oct/73, 46;  Jun/74, 88;  Nov/73, 59;  Jul/74, 30.  22  Figure 5.  Size of reproductive (ovigerous or mating) females collected at Crescent Beach. each month.  Results averaged f o r  Data are presented f o r months i n which  5 or more reproductive females were c o l l e c t e d . A , means;  v e r t i c a l distance from mean to nearest  horizontal mark represents one sample standard deviation;  outer marks represent the range of  values obtained;  numbers beside triangles repre-  sent the numbers of individuals measured i n each month.  23  o un  in  o  -<H=—I  1  hU  o 00  b  <  in  ccl  K! K  d  ^  crj al  (m) H13N31 LTV3H  O  of o  CD  o  24  F i g u r e 6.  Brood  s i z e v e r s u s female s i z e d a t a f o r a n i m a l s  c o l l e c t e d a t C r e s c e n t Beach. s e n t s one  female.  Each p o i n t r e p r e -  25  OCT/73  NOV/73 N=8  N=1G  nIBO. co-  aoo.  ISO-.  100-I  1B3..L  140. M iao. LT) lflOv  •  133 UDO  O0-.  so  GO..  50  40v  •50  33».  3D  0-. •a  -4-  -t-  i - i  i-3  i  i-s  i-7  0  0-9  DEC/73 ( + ) , FEB/74- CX) 200  330  ISO  IBO  1B0-1  iBO-J. 140  M ISO. LT) 100.  133  1-3  1-5  1-7  v  44-  100-1 SO  80-1 GO  eo.i  40  40  4 +-  4-  -41-3  1-5  1.7  1-5  -4 1 1-7  so  EO 0  .  MAR/74 N=20  140.  a  1.1  1-9  -+-  0 o-a  -4-+i ' l ' 1-3  APR/74 N=30  L i  MAY/74 N-35 330  ISO.  1£0  ISO-  leo-J.  ft "°I-I  H  140  iao-  iao  100-  100  0 0  • +  S3  + +4  0 -40-9  —4  1-7  ISO 140  4- ++4 +.44- 4-  iaD. 00  0  133  T  100  so  1-3  lSO-J.  140.  40-  +  330-  V  IBO-  so  1-1  4-4-  JUL/74 N=29  ISO  t-4  +4  40  + +  +  JUN/74 N=31 BOO  ++  GO  4> +*++ + o. 4•4-4•9 •+- 1-1 -4- 1-3 +  ao-  44 14? *  BO-l  +  100 03 SO.l  + +  + 4f 4-  40.J. 33  H  1-1  1-  -41-3  1-5  -4-  HEAD LENGTH (MM)  —i  1-7  1  O 0-9  4*+  4*  +4-  -4. 1-1-4-  1.3  1-5  HEAD LENGTH (MM)  1-7  26  IV.  LABORATORY STUDIES  A.  METHODS  1.  Maintenance of Amphipods Amphipods were maintained  i n the laboratory at 10 and 20° C.  medium was u n f i l t e r e d seawater (ca. 24-28%^ .  The  The amphipods were  kept i n glass stacking dishes and beakers of various s i z e s , ranging in volume from 100 ml (for 1-2 animals) to 1 1 (several animals). Mass cultures were kept i n glass aquaria (5-10 1 seawater) and p l a s t i c dishes (ca. 6 1).  Cultures were not usually aerated;  t h i s resulted  i n m o r t a l i t i e s i n some mass cultures when the water became fouled, ( i . e . , cloudy, with a surface scum) by r o t t i n g algae, or when cultures were overcrowded.  Enteromorpha (collected at Crescent Beach) was  provided i n excess amounts for food.  Small rocks and. plant material  (Enteromorpha and Zostera) served as refuges.  Cultures were illuminated  13 h/day. Under laboratory conditions mating occurred  spontaneously.  However, broods did not always develop to hatching.  The reasons for  these brood f a i l u r e s were not determined. Recently hatched young sometimes became^ caught i n the surface f i l m where they died i f not removed.  This u s u a l l y occurred with ca.  10-25% of the young i n a brood, although sometimes, almost an entire brood became caught.  2.  Length-Weight Relationships The head length to dry weight relationship for A. pugettensis  was determined from measurements of animals from laboratory cultures. Dry weights were obtained by r i n s i n g animals i n d i s t i l l e d water and  then drying them at 60° C overnight. The ash content was obtained by heating animals i n a muffle furnace at 600° C f o r 4-6 h.  The carbon  content of animals was estimated as one-half of the ash-free dry weight (see Parsons and Takahashi 1973).  3.  Tolerance Experiments In a l l tolerance experiments, animals were acclimated f o r  at least 2 weeks to 10 or 20° C (24%^ and provided with excess food (Enteromorpha). For the determination of high temperature tolerances, individuals were placed i n 150 ml beakers containing 100 ml f i l t e r e d  seawater  <p;ore size 0.45 ym) at the temperature of acclimation (24%^).  The  beakers were then placed i n a water bath set at the test temperature (24, 27, or 30° C). Animals were l e f t at the test temperature f o r 24 h, then returned to the acclimation temperature, and checked f o r survival 16 h l a t e r .  Low temperature tolerances over 24 h were not  determined. For s a l i n i t y tolerance t e s t s , individuals were transferred d i r e c t l y from the acclimation temperature and s a l i n i t y to ca. 100 ml f i l t e r e d seawater at the test s a l i n i t y (0, 3, 5, 7, and 40%^  no  temperature change) . After 24 h, animals were returned to 24%,. Survival was checked 16 h l a t e r .  Low s a l i n i t i e s were obtained by  d i l u t i o n of seawater at room temperature. In the temperature and s a l i n i t y tolerance experiments, the LD5Q-24 h was the temperature or s a l i n i t y that resulted i n the deaths of 50% of the tested animals after 24 h exposure. An i n d i c a t i o n of the tolerance to anoxic conditions was deter-  mined from the survival of individuals i n 5 ml f i l t e r e d , (10 or 20° C, 24%.} to which ca. 0.5 mg Na S0 2  3  seawater  had been added.  Sodium  s u l f i t e removes oxygen from solution, but i s also poisonous i n high concentrations.  Therefore, these tests may  poison as well as the effects of anoxia. to these conditions for 1, 2, or 3 h.  show the e f f e c t s of the  The animals were exposed  The animals were then trans-  ferred to aerated seawater and survival was checked 16 h l a t e r . Survival out of water i n moist a i r was measured by b l o t t i n g o animals on f i l t e r paper to remove excess water, and then placing them i n a 150 ml beaker (no water) which was placed i n a sealed 600 ml beaker to which 100 ml seawater was added.  Survival was  checked hourly (less frequently near the start and end of the experiment) . Survival of animals i n the absence of food was determined by placing individuals i n ca. 100 ml f i l t e r e d seawater, without food (at  the acclimation temperature and s a l i n i t y ) .  Survival was checked  daily. In the anoxia, survival out of water, and survival without food experiments, the L T ^ was the time required for 50% of the tested animals to d i e . In a l l tolerance experiments, the c r i t e r i o n for death was the absence of movement when touched.  4.  Effect of Temperature on Incubation Time The incubation time was measured as the time i n days from  copulation u n t i l the f i r s t young were released by the female.  Mating  pairs were isolated i n 100-250 ml seawater at 10 and 20° C (24%^ and  supplied with, excess amounts of Enteromorpha.  After copulation, the  male was removed.  5.  E f f e c t s of Temperature and S a l i n i t y on Growth Growth of young from the time of release from the female to adult  size was measured at 10 and 20° C i n f i l t e r e d seawater at 24-28, 18-21, and 12-14%o.  Animals were fed excess amounts of Enteromorpha.  Experi-  ments at 10° C were continued for 15 weeks, and those at 20° C for 12 weeks.  Experiments were conducted i n transparent p l a s t i c , compart-  mentalized boxes (Vlchek P l a s t i c s "Trans-box" P824) , with one animal/ compartment.  Each compartment was 5.3 X 5.3 X 5.3 mm,  f i l l e d with ca.  100 ml seawater. Experimental animals were from broods released i n the laboratory within 48 h prior to the start of each experiment.  Each animal was  measured (head length) and moved to a clean container with fresh f i l t e r e d seawater and excess food every 7 days.  Periodic checks were  made between measurement times to check food supplies and to note deaths.  6.  Effects of Temperature, S a l i n i t y , and Oxygen Levels on Oxygen Consumption Oxygen consumption was measured with a YSI Model 53 B i o l o g i c a l  Oxygen Monitor (2 Ag-Pt electrodes, KC1 e l e c t r o l y t e , and Teflon membranes).  The experimental chambers were glass v i a l s f i l l e d with  4-10 ml f i l t e r e d seawater, depending upon the size of the animal tested and the test temperature.  The experimental chamber was  divided into 2 portions by a nylon screen (mesh size ca. 0.5  mm).  30  One amphipod was placed i n the lower chamber, and a magnetic bar was placed i n the upper chamber;  stirring  the t i p of the electrode protruded  into the upper chamber (similar to the set-up of Teal and Halcrow 1962) . A control chamber, i d e n t i c a l to the experimental v i a l s except that no amphipod was present, was run concurrently with each experimental chamber.  The experimental and control chambers were placed i n a  constant temperature water bath.  Tests were done i n subdued l i g h t .  Following each t e s t , dry weights of amphipods were obtained (see section IV.A.2). For tests of the effects of temperature and s a l i n i t y on the oxygen uptake, animals were kept at the acclimation temperatures and s a l i n i t i e s , and provided with excess food, for at l e a s t 2 weeks prior to the tests, and were kept i n the experimental v i a l s at the test temperatures and s a l i n i t i e s for ca. 30 min p r i o r to the t e s t s . The water i n experimental and control chambers was approximately saturated with oxygen at the start of the temperature and  salinity  tests, and was not allowed to f a l l to l e s s than 70% saturation. Tests were run u n t i l the animal showed a constant oxygen uptake rate for ca. 30 min.  Although the animals were r e s t r i c t e d i n their movements  by the size of the chambers, the action of the s t i r r i n g bar i n moving the water usually stimulated the amphipod to become active, although the amount of a c t i v i t y varied greatly between i n d i v i d u a l s .  Oxygen  uptake was expressed i n u l / h and ul/mg dry wt/h. To test for theeeffects of temperature on oxygen consumption, amphipods acclimated to 10° C were tested at 0, 5, 10, 20, and 25° C, and animals acclimated to 20° C were tested at 5, 10, 20, 25, and 30° C (24%^ .  Individuals were warmed or cooled to the test temperatures  31  Q ^ Q values were calculated  (where necessary) over ca. 10-15 min. log Q  1Q  = (10(log V  (base 10 logs) where V t  x  (Winberg  2  2  and  - log V ) ) / ( t 1  2  as  - t)  (1)  ±  are the rates at temperatures t  2  and  1971).  To test the effects of s a l i n i t y on r e s p i r a t i o n rates, amphipods were acclimated at 10° C to 24, 18, or 12 %,, and then tested at the acclimated temperature and s a l i n i t y .  Also, some animals acclimated  to 24%owere moved d i r e c t l y into 12%„ and tested at t h i s s a l i n i t y after 30 min. The effect of the environmental oxygen l e v e l on the oxygen uptake rate at 10° C (24%^ was measured by recording the decrease i n the oxygen l e v e l caused by an amphipod placed i n a closed test chamber (4 ml f i l t e r e d seawater).  The water was s t i r r e d throughout the tests  The water was close to oxygen saturation at the start of each t e s t . Each test lasted for ca. 6-8 h.  Animals were acclimated to 10° C,  24%»for at least 2 weeks,.and were placed i n the test chamber ca. 1 h p r i o r to the start of measurements. r e s u l t s averaged. intervals.  Seven adults were tested, and the  Oxygen uptake was calculated  at 10% oxygen saturation  In order to compare r e s u l t s from different sized animals,  oxygen consumption rates at each oxygen l e v e l were expressed as percentages of the rate shown by the same animal at 80% oxygen saturat i o n (this i s approximately the oxygen l e v e l i n the temperature and s a l i n i t y e f f e c t experiments). h/oxygen available)  7.  were  Oxygen u t i l i z a t i o n rates (oxygen uptake/  calculated.  Feeding Experiments a.  Feeding Experiments with Adults  32  Four to s i x adults were placed i n a small stacking dish (ca. 250 ml f i l t e r e d seawater, 10 or 20° C, 24%^ with excess amounts of a food type.  Survival of amphipods, disappearance of food, and presence  of f e c a l p e l l e t s were examined over 1 week to determine a c c e p t a b i l i t y of foods.  Three or more t r i a l s were done for each food.  tested were:  The foods  "Tetramin Staple Flake Food" ( t r o p i c a l f i s h feed);  "Clarke's New-Age Crumbles" (trout p e l l e t feed);  frozen brine shrimp  (Artemia), frozen f i s h f l e s h (juvenile sockeye salmon);  the seaweeds  Ulva sp., Enteromorpha i n t e s t i n a l i s , Fucus sp., Chondria decipiens, and dead Zostera marina ( a l l collected at Crescent Beach); benthic diatoms (predominantly Nitzschia sp.; aquaria);  clumps of  collected from seawater  and d e t r i t u s collected from the substrate of tidepools at  Crescent Beach ( p a r t i c l e s mostly < 0.1mm  diameter). Plant foods had  various microorganisms associated with them. b.  Effect of Food Type on Growth  Young were fed from the time of release from the female up to adult size, on the same foods as i n section IV.A.7b, except that Chondria was not tested.  Some animals were given a food choice  consisting of brine shrimp, Enteromorpha, benthic diatoms, and Zostera. Fish.and seaweeds were given i n small pieces, especially to young animals.  Experiments were done at 10 and 20° C (24%^. Experimental  vessels and measurement procedures were as i n section IV.A.5. Because there were i n s u f f i c i e n t numbers of each sex for each food type, and because many amphipods died at sizes too small to allow sexing, thedat'a for both sexes are combined and presented u n t i l an average head length of 0.9 mm was attained, or u n t i l a l l animals died. Both sexes grow at approximately the same rate up to t h i s s i z e , which i s the minimum adult size.  33  c.  Egestion Rates  Animals were acclimated to 20° C (24%^> with excess food (Enteromorpha) f o r at least 2 weeks. f i l t e r e d seawater  Individuals were then placed i n 100 ml  (20° C, 24%i> with excess Enteromorpha.  Fecal p e l l e t s  were removed by Pasteur pipette after 24 h, rinsed i n isotonic ammonium formate (to remove adventitious s a l t s ) , dried at 60° C, and weighed. d.  Assimilation E f f i c i e n c i e s  Animals were acclimated at 10 or 20° C(i(24%^ with excess Enteromorpha  i n t e s t i n a l i s for at least 2 weeks.  Assimilation e f f i -  ciencies f o r adults feeding on E. i n t e s t i n a l i s at 10 and 20° C (24%^) , and on the benthic diatom mixture at 10° C (24%0 were measured by two methods.  For both foods, associated microorganisms were probably  ingested along with the plant material. The f i r s t method used the radioisotope ^ C .  Plant foods were  incubated f o r 1 week i n enriched f i l t e r e d seawater medium containing NaHC0 l a b e l l e d with 3  1 4  C  (20 yCi/250 ml medium).  The l a b e l l e d food  was rinsed several times i n f i l t e r e d seawater before being used. Individual animals plus excess amounts of l a b e l l e d food were placed in sealed 125 ml Erlenmyer f l a s k s containing 140 ml f i l t e r e d  seawater.  Flasks were incubated i n the dark for 10-16 h (depending on the feeding rate).  Each animal was then transferred to a second f l a s k containing  unlabelled food to allow the animal to clear i t s gut of l a b e l l e d food. After 7-16 h, the experiment was terminated.  The amounts of ^C- i n  solution, i n feces i n both f l a s k s , and i n the animal were measured by l i q u i d s c i n t i l l a t i o n counting.  Feces and animals were rinsed i n  f i l t e r e d seawater before measurement.  The amount of -^C released by  labelled food i n the absence of feeding amphipods, and the amount of  34  -^C released into the medium by l a b e l l e d feces, were measured i n control experiments. A  The assimilation e f f i c i e n c y (A, %) was calculated as  f  * - • 100 s + a + f  (2) '  +  v  where s_ was the a c t i v i t y i n solution i n both flasks combined (corrected for controls), a was the a c t i v i t y of the animal, and f_was the a c t i v i t y in feces i n both f l a s k s combined (corrected for controls).  The corrected  value of j3 was assumed to represent l a b e l released by the animal due to r e s p i r a t i o n or excretion. Assimilation e f f i c i e n c i e s were also measured by the method of t  Conover  (1966).  This method i s based on the assumption that the ash  f r a c t i o n of the food i s not assimilated by the animal.  The assimilation  e f f i c i e n c y (U, %) was calculated as U  - (1 -" )F F  E  •  1  0  <3>  0  where F i s the r a t i o of the ash-free dry weight to the dry weight i n the food, and E i s the same r a t i o f o r the feces.  Amphipods were kept  i n f i l t e r e d seawater and provided with excess food.  Feces were collected  after 24 h with a Pasteur pipette, rinsed several times i n isotonic ammonium formate, dried overnight at 60° C, and weighed. were determined by heating feces at 450° C for ca. 5 h. 4-6 animals were combined into a single  8.  Ash weights Feces from  sample.  Growth E f f i c i e n c i e s The net growth e f f i c i e n c e s (K^, %) were estimated for animals  raised on Enteromorpha  at 10 and 20° C i n 100% seawater as  where G was the growth rate and T was the metabolic rate, both expressed  35  i n mg C/day (Winberg 1971). The growth rate (G) was estimated from the growth experiment (section IV.B.4).  data  Growth i n length was converted to growth i n dry  weight and carbon content using the length-weight relationships (section IV.B.l).  Growth rates were estimated over weekly i n t e r v a l s .  The absolute growth rate (mg C/day) was estimated as G(mg  C/day) = g g ) ~_ ° g >  ( 5  )  and the weight-specific growth rate, as a percentage of the t o t a l body carbon per day, was estimated as r m G ( / o )  - In C(2) - In C(l) " t«2) - t ( l )  ,. ( 6 )  (ln = natural logs) where C(l) and C(2) were the carbon contents of the animals at times t ( l ) and t(2) (Winberg 1971). The absolute ( i n mg C/day) and weight-specific ( i n % body C/day) metabolic rates (T) were estimated from the oxygen uptake rates f o r animals acclimated and tested at 10° C and acclimated and tested at 20° C (24%^.  Oxygen uptake i n volume of oxygen was converted to mg  carbon by the formula mg C = ml 0  2  • 2^74  'Q R  () 7  with RQ assumed to be 1 (Parsons and Takahashi 1973). The assimilated ration was estimated as the sum of growth (G) and metabolism (T). The gross growth e f f i c i e n c e s (K^, %) were estimated as 1^ = A • K  2  where A was the assimilation e f f i c i e n c y .  (8)  B.  RESULTS  1.  Length-Weight  Relationships  The relationship between head length and dry body weight i s shown i n F i g . 7.  The relationship between dry body weight and  ash-free dry body weight i s shown i n F i g . 8.  2.  Tolerance Experiments a.  Temperature  The survival after 24 h exposure to high temperatures i s shown in Table I I .  The LD -24 h was between 24 and 27° C f o r animals 5Q  acclimated to 10° C, and between 27 and 30° C for animals acclimated to 20° C.  Animals could be kept several weeks at 5-20° C.  See also  section IV.B.5a. b.  Salinity  The survival of animals a f t e r 24 h exposure to high and low s a l i n i t i e s i s shown i n Table I I I .  The low s a l i n i t y LD5Q-24 h at  10° C (animals acclimated to 10° C, 24%^ was between 3 and 5%* and at 20° C (animals acclimated to 20° C, 24%^, between 5 and 7%»  At  both temperatures, the high s a l i n i t y LD^o-24'.ih was greater than 40%» Animals could be kept several weeks at 12-28%, (10 or 20° C ) . c.  Low Oxygen  The survival of animals at 10° C i n anoxic conditions (caused by the addition of sodium s u l f i t e ) i s shown i n Table I V . was between 2 and 3 h. h;  4 of these survived.  The LT^Q  At 20° C, 8 individuals were tested f o r 1 At both temperatures, once anoxic condi-  tions were established, a l l individuals became paralyzed, and remained so throughout the exposure.  37  Figure 7.  The relationship between head length and dry weight for A. pugettensis.  (Base 10 logarithms)  38  39  Figure 8 .  The relationship between dry weight and ash-free dry weight i n A. pugettensis.  (Base 10 logarithms)  40  •DRY  LOG  WT-  VS  ASH-FREE  Y = -CM0E3  DRY  + 0-3037  I-  o-i DRY  WEIGHT  WT-  » LOG X  io(MG)  so-  41  Table I I .  Survival at high temperatures a f t e r 24 h exposure (24%^.  Acclimation to 10° C Test  Temperature  Acclimation to 20° C  n  Number Surviving  n  Number Surviving  24  16  14  16  16  27  16  6  16  16  30  16  0  16  0  (°c)  Table I I I .  Survival at high and low s a l i n i t y a f t e r 24 h exposure  Acclimation to 10° C, 24%.  Acclimation to 20° C,  24%o  Test S a l i n i t y (%»)  n  Number Surviving  n  Number Surviving  0  18  0  18  0  3  18  8  18  0  5  18  12  18  5  7  18  18  18  16  40  18  17  18  10  Table IV.  Survival i n anoxic conditions induced by the addition of sodium s u l f i t e (10° C, 24%^.  Duration of Exposure  n  Number Surviving  1  9  9  2  9  6  3  9  2  d.  Survival i n Moist A i r  The LTCJQ f o r survival i n moist a i r was 3 2 - 3 3 h at 1 0 ° C (range, 26-98 h;  e.  n = 1 0 ) , and  15-17 h at 20° C (range,. <14-25 h;  n = 10).  Survival i n the Absence of Food  The LT^Q for survival i n the absence of food was 17-20 days at 1 0 ° C (range, 9-35 days; <6-15 days;  n = 8).  n = 1 1 ) , and 6-11 days at 20° C (range,  In starved animals, material i n the anterior  part of the gut was not egested as f e c a l p e l l e t s , but appeared to disappear from the gut gradually over a number of days.  This material"  was probably assimilated to a higher degree than i n normally fed individuals.  3.  Effects of Temperature on Incubation Time For broods that developed from f e r t i l i z a t i o n to release from  the female i n the laboratory, the incubation time was 14-16 days (n = 9) at 1 0 ° C, and 9-10 days (n = 14) at 20° C.  This represents  a QIQ f o r the average brood development rate of ca. 1.5.  4.  Effects of Temperature and S a l i n i t y on Growth The growth i n head length of animals feeding on Enteromorpha  at d i f f e r e n t temperature-salinity combinations i s shown i n F i g . 9 and Appendix B.  These figures show only r e s u l t s for animals that sur-  vived to the end of the experiment.  There was no effect of tempera-  ture or s a l i n i t y on survival up to 0.9 mm head length ( 6 7 - 7 6 % s u r v i v a l , not including animals caught on surface f i l m ) .  Mortality  between 10 and 15 weeks age was 4% at 1 0 ° C, and at least 29% at 20° C (the l a t t e r f i g u r e may be low, since not a l l 2 0 ° C animals were kept a l i v e past 12 weeks age).  43  Figure 9.  Growth i n length at d i f f e r e n t temperatures and s a l i n i t i e s . Mean values. intestinalis.  (See Appendix B). +, 10° C;  , 18-21%, ;  Food:  x, 20° C; -, 12-14%. .  Enteromorpha , 24-28%. ;  MALES  a  l.a,  1-4.  f UJ  1«0.  o-ai  x 0.4L  O-El 0-0.  t——t—t—»:—t—t— • 1 1 1 1 1 1 1 0. 1. £• 3- 4. 5« 6' 7« 8- 9« 10- 11. 12. 13- 14. 151  WEEKS b  FEMALES  1-B  ±•41  2  1-21  j£  1-0.  in UJ  5  o-ai o-ej.  UJ X  0-4L  O-El 0-0.  H  1  !• a-  1  1  1  1  3- 4. 5- 6-  1  1  7.  a. 9- 10- 11. IE. 13. 14- i s .  WEEKS  1  1  \  1  1  1  1  45  Males and females showed similar growth rates up to ca. 0.8-0.9 mm head length (except at 12-14%,} , a f t e r which males grew faster than females. S a l i n i t i e s of 12-28%ohad no marked effect on growth at 10 or 20° C. ties.  Temperature did have a large effect on growth at a l l s a l i n i The time required to reach 0.9 mm head length averaged 8-9  weeks at 10° C, and 4-5 weeks at 20° C.  This represents a Q-^Q f o r  average growth from time of release from female up to 0.9 mm of ca. 1.9.  5.  Effects of Temperature, S a l i n i t y , and Oxygen Levels on Oxygen Consumption The relationship between oxygen uptake and dry body weight was  a log-log relationship with oxygen uptake per animal increasing with increasing weight;  weight-specific oxygen uptake decreased  with increasing body weight (Appendix C).  Data includes both sexes;  there was no apparent effect of sex on oxygen uptake (except as a result of size differences). a.  The Effect of Temperature  Increased test temperatures resulted i n increased oxygen consumpt i o n (Fig. 10). temperatures.  There was also greater a c t i v i t y at higher test  Acclimation temperatures had no s i g n i f i c a n t effect on  the oxygen uptake at test temperatures of 10 or 20° C.  At high test  temperatures, the lower acclimation resulted i n higher oxygen uptake, especially i n larger individuals;  at 30° C, animals acclimated to  10° C become paralyzed. In tests at 5° C, the higher acclimation temperature resulted i n lower oxygen consumption by larger animals,  46  Figure 10.  The effect of acclimation and test temperature on oxygen consumption. Appendix D.  S a l i n i t y , . 24%o.  Values were obtained from  , animals acclimated to 10° C;  , animals acclimated to 20° C;  +, 0.5 mg dry body  weight;  x, 1.0 mg dry body weight;  A, 5.0 mg dry body  weight;  numbers on graph are Q^Q values between the  two nearest test temperatures f o r animals acclimated to the same temperature.  47  1  but l i t t l e difference f o r smaller individuals; acclimated to 20° C became paralyzed. Fig.  10.  at 0° C, animals  The Q^Q values are shown i n  Values were low between test temperatures of 10 and 20° C,  increasing at test temperatures outside t h i s range.  The Q^Q between  10 and 20° C f o r animals acclimated to the test temperature  was  1.3 for animals of 0.5-5.0 mg dry weight. b.  The Effect of S a l i n i t y  Short or long term exposures to s a l i n i t i e s of 12-24%.did not affect the relationship between oxygen uptake and body weight at 10° C  (Table V). c.  The Effect of Oxygen Level  The oxygen uptake rate f e l l as the oxygen l e v e l f e l l i n these short term tests except below a certain oxygen l e v e l .  Below t h i s  l e v e l the amphipods showed a constant, low oxygen uptake rate u n t i l near zero oxygen l e v e l s (less than 2% saturation) were reached, after which, no oxygen uptake occurred.  During the constant uptake and  zero uptake stages, the , animals remained paralyzed, showing no 1  a c t i v i t y other than occasional twitching of the pleopods; higher oxygen l e v e l s , animals did show a c t i v i t y .  at  If moved to  aerated water soon after paralysis occurred, animals usually recovered immediately;  after 1 h or more paralyzed, recovery did not occur.  This implies a shorter tolerance to anoxic conditions thaii i n the sodium s u l f i t e tests (section IV.B.2c);  t h i s can be attributed to  the stress conditions experienced by animals i n the present tests in the low oxygen conditions prior to the onset of p a r a l y s i s .  The  l e v e l at which paralysis occurred ranged from 28% to less than 2% oxygen saturation.  This v a r i a b i l i t y may be related to acclimated  Table V.  The effect of s a l i n i t y (at 10° C) on the r e l a t i o n s h i p between oxygen uptake per animal and dry body weight. Regression equations are of the form Log T = a + b(Log W) where T i s the oxygen uptake i n m i c r o l i t r e s of oxygen per animal per hour, W i s the dry body weight i n mg, a_ i s the y-intercept, and b_ i s the slope of the l i n e ; logarithms are base 10. Analysis of covariance: comparison of slopes, p = 0.46; comparison of yintercepts, p = 0.53. Common slope: 0.73.  Acclimation Salinity (%. )  Test Salinity (%. )  !£•  12.  19  0.55  0.67  0.84  1-8  178  14  0.36  0.92  0.76  124;  15  0.48  0.74  0.93  52V  16  0.47  0.72  0.82  I2'4i  n  a  b  r^  oxygen conditions (these were not s t r i c t l y controlled). The change i n oxygen uptake rates i n decreasing oxygen l e v e l s i s shown i n F i g . 11a. Fig. l i b .  The oxygen u t i l i z a t i o n rates are shown i n  The higher u t i l i z a t i o n rates shown at low oxygen l e v e l s ,  even when paralyzed, may be partly due to the constant s t i r r i n g of the medium during the tests.  6.  Feeding Experiments a.  Feeding Experiments with Various Foods  The survival (not including animals dead on surface film) and growth of young on various foods are shown i n F i g . 12. faster at 20° C than at 10° C with a l l foods.  Growth was  The best growth and  survival of young among individual foods was shown with Enteromorpha and benthic diatoms.  These foods were also usually eaten by adults.  For Enteromorpha, small t h a l l i were best f o r youngest amphipods.  In  another experiment with the same benthic diatoms, 0.9 mm head length was reached at between 3 and 4 weeks age (cf. 5 weeks i n the present study) with 4 of 5 surviving (Chang and Parsons 1975;  note : diatom  species was Nitzschia, not Pseudonitzschia). There was v a r i a b i l i t y i n results with both young and adults feeding on Fucus.  This appeared to be due to v a r i a b i l i t y i n the  texture of the Fucus used i n the experiments:  s o f t , r o t t i n g plant  was eaten by adults, and supported growth of young; was not eaten. adults;  fresh plant  Ulva and dead Zostera were usually not eaten by  neither alga supported growth of young animals to 0.9 mm  head length, although Zostera did support survival f o r several weeks, but with poor growth.  Chondria was not ingested by adults;  51  Figure 11.  Oxygen consumption i n decreasing (a)  oxygen l e v e l s at 10° C.  x-axis, oxygen l e v e l as a percentage of the satura-  tion level;  y-axis, oxygen uptake as a percentage of  the consumption per animal per hour shown by the animal at 80% saturation. tion;  (b)  x-axis, percent oxygen satura-  y-axis, oxygen u t i l i z a t i o n expressed as the  oxygen uptake per animal per hour divided by the amount of oxygen i n the test vessels, i n percent.  Individuals  were allowed to consume the oxygen i n a closed u n t i l no oxygen was l e f t ;  container  oxygen uptake rates were  calculated at 10% intervals of oxygen saturation, mean of 7 animals;  v e r t i c a l bars represent  x,  one sample  standard deviation on eigher side of the mean.  53  F i g u r e 12.  Growth i n head l e n g t h w i t h v a r i o u s were c o n t i n u e d was  attained  occurred , 20  foods.  Experiments.  u n t i l an average head l e n g t h of 0.9  mm  (or u n t i l a l l i n d i v i d u a l s d i e d i f t h i s  first).  x, mean;  C(24%„);  , 10 C (24%« ) ; -, 0.9  mm  head  length.  Number b e s i d e mean i s the number of animals s u r v i v i n g . V e r t i c a l l i n e s represent  one  on e i t h e r s i d e of the means. s u r f a c e f i l m not  included.  sample standard  deviation  Animals t h a t d i e d on  the  a  10 C, N=10; 20 C , N=13  TETRAMIN  1-0.  o-ai 5  *  /f  7  41  f  #  7  1  •^3  1  o-ai  H  b  h  H  TROUT PELLET FEED  1-  10'  1  IOC,.N=IO;  WEEKS  1  12-  20  14-  C,  N - H  j  IB-  1  18-  1  20-  FISH  C  (FROZEN)  10 c, N-IO 20 c, N - » :  ^3  O-Bl  x H  U  0-6  • _1  T  41  X Q-*J-  5  8«  d  F R O Z E N B R I N E SHRIMP  10-  12-  14"  . IB*  10 c, H-IO 20 c, N = U ;  WEEKS  IB-  e  f  FUCUS  DIATOMS  10 C, H-lOj 20 C,  14.  IB.  IB"  20.  14.  IB-  IB-  20.  10 C, N=9; 20 C, N=14  B.  1X3.  WEEKS  12.  g  ULVA  10 C, H-10; 20 C, N-16  1-0.  1  o-ai  ID  O-B!  5 -4i  8^-'S  o-o.0-  H 2'  X,  f-  H B-  1  10-  H 12-  _|  14-  1  16"  1  IB-  1  20-  58  ZOSTERA  %  10 C , !<-&;  20 C , N-14  o-aj.  I  • x  4 o.si  0-0.  J  H  1  DETRITUS  1  1 8-  1 10.  1 IE.  1 14-  1 IB'  1 IB-  1 ED-  1 IE-  1 14-  1 IB*  1 IB*  1 SO-  10 C, N=6; 20 C, N=12  Li*  ±•01  O-Ei  O.Qj 0.  1 E-  .—| 4-  1 6-  1 B-  1 ID-  Z/EEKS  WEEKS  i n an e a r l i e r experiment, some young survived 6 weeks on this plant, but with poor growth (maximum head length attained, 0.6 mm; Chang and Parsons 1975).  The survival of some animals f o r several weeks  with Zostera and Chondria was probably due to ingestion of epiphytic organisms, as the host plant was not reduced by grazing. On plants that were ingested, epiphytes may also be a n u t r i t i o n a l source. Pish feeds and animal f l e s h were readily eaten by adults.  Some  young grew to maturity on these foods, but growth was slower (espec i a l l y for trout p e l l e t feed), and survival was poor, especially f o r the smallest amphipods.  In an e a r l i e r experiment, 0.9 mm was reached  in 5-6 weeks at 20° C with p e l l e t feed and turbot f l e s h (cf. present study) with poor survival (Chang and Parsons 1975).  Deaths i n older  animals fed f i s h feeds and f l e s h were due to fouling of the medium when too much food was added. eaten:-  Other animals foods could also be  cannibalism sometimes occurred i n cultures, e s p e c i a l l y when  other food was scarce; molts were eaten after each molting. few f e c a l p e l l e t s were produced when fed animals f l e s h ;  Very  with plant  foods, numerous f e c a l p e l l e t s were egested. Tidepool d e t r i t u s supported slow growth of young animals to mature s i z e , but with poor s u r v i v a l .  The amount of detritus that  was supplied may have contained i n s u f f i c i e n t organic matter. Animals supplied with a choice of frozen brine shrimp, Enteromorpha, benthic diatoms, and Zostera showed s l i g h t l y faster growth than animals fed Enteromorpha.or  diatoms alone;  numbers were  i n s u f f i c i e n t to determine i f t h i s difference was s i g n i f i c a n t . 10° C, survival with the food choice was low; fouling of the medium by the brine shrimp.  At  t h i s was due to  Brine shrimp was the  f i r s t eaten by adults;  Enteromorpha (small t h a l l i ) and diatoms were  f i r s t eaten by young;  Zostera was usually not eaten, except by some  adults when a l l other foods had been eaten. Enteromorpha also supported reproduction i n laboratory cultures. The a b i l i t y of other foods to support reproduction was not studied. b.  Egestion Rates  Egestion rates over 24 h at 20° C were extremely variable (Fig. 13).  Qualitative observations indicated that feeding and  rates were higher at 20° C than at 10° C.  egestion  Preliminary experiments  over 2 and 3 days also showed large v a r i a b i l i t y i n egestion rates, c.  Assimilation E f f i c i e n c i e s  The estimates of a s s i m i l a t i o n e f f i c i e n c y of organic matter by adult A. pugettensis feeding on Enteromorpha and diatoms are shown i n Table VI.  For Enteromorpha, both methods produced nearly i d e n t i -  cal results.  The v a r i a b i l i t y within each method was large.  assimilation e f f i c i e n c y at .20° C was at 10° C ( t - t e s t , p = 0.01,  for C 1 4  The  s i g n i f i c a n t l y lower than that results).  methods produced quite d i f f e r e n t r e s u l t s ;  the  For diatoms, the  two  method gave much  higher e f f i c i e n c i e s .  7.  Estimates of Growth E f f i c i e n c y a.  Growth Rates  Growth i n length when fed Enteromorpha at 10 and 20° C i n 24%» (see F i g . 11), converted to growth i n dry body weight, i s shown i n F i g . 14.  The absolute and weight-specific growth rates, i n mg C/day,  calculated over weekly i n t e r v a l s , are shown i n F i g . 15.  Absolute  growth rates increased at a decreasing rate as body weight increased.  62.  F i g u r e 13.  E g e s t i o n r a t e s (mg C/day) a t 20° C. intestinalis. The  carbon  Food:  F e c a l p e l l e t s were c o l l e c t e d  Enteromorpha a f t e r 24 h.  c o n t e n t of the f e c a l p e l l e t s was assumed to  be o n e - h a l f the a s h - f r e e d r y weight.  The d r y weights o f  the amphipods were o b t a i n e d by c o n v e r s i o n of head l e n g t h s (see F i g . 7 ) .  x, males;  +,  females.  = 20  T  C  O-EL  + +  0-41  +X  X  o.aL  X X X  x<  +  o-aL  + o-iL  X X +  X X  +  ++  + +  n . o } x + + f , +  -H-  +,+  X  x+  x  8-  •RY  WEIGHT  (MG)  1D>  11.  12  64  Table VI. Assimilation e f f i c i e n c i e s  14  Food; ash content i n % (xlSD)  Temp (C)  n  c  (A) of adults.  o  Methods-  Conover Method  Dry wt. amphipods (xlSD)  A (%) (xtSD)  n  A (%) (xiSD)  Enteromorpha intestinalis  10  14  5.410.87  7719.4  8  7716.4  Enteromorpha intestinalis  20  14  5.511.00  6819.1  8  66115.2  Benthic diatoms (Nitzschia sp.)  10  10  5.010.66  82+6.0  5  4615.3  (17.1±3.48)  (17.113.48)  (45.813.34)'  ^  n i s the number of individuals; n i s the number of t r i a l s ; of 4-6 adults  dry wt.estimated from head length  each t r i a l represents the pooled r e s u l t s  65  Weight-specific growth rates decreased at a decreasing rate as body weight increased.  Males showed higher growth rates than females,  e s p e c i a l l y at body weights greater than c_a. 1 mg dry weight (which i s the approximate minimum size of mature females).  Growth rates  were higher at 20° C than at 10° C for animals smaller than ca. 3.5 mg dry weight; at 10° b.  for larger animals, growth rates were higher  C. Metabolic Rates  The oxygen uptake rates at 10 and 20° C i n 24-%l% seawater (from Appendix C), expressed i n mg C/day (males and females combined) are shown i n F i g . 16.  Absolute metabolic rates increased at a decreasing  rate as the body weight increased;  weight-specific rates decreased  at a decreasing rate as body weight increased. were higher at 20° C than at 10° c.  Oxygen uptake rates  C.  Assimilated Ration  The absolute and weight-specific assimilated r a t i o n s , as  estimated  by the sum of the growth and oxygen uptake rates, are shown i n F i g . 17.  The absolute assimilated r a t i o n increased at a decreasing rate  as body weight increased;  the weight-specific assimilated r a t i o n  decreased at a decreasing rate as body weight increased.  The assimi-  lated r a t i o n was higher for males than for females, except at the smallest sizes.  At 20° C, the assimilated r a t i o n was higher than at  10° C, but at weights greater than ca. 3.5 mg,  the values at 10° C  approached those at 20° C. d.  Growth E f f i c i e n c i e s  The net growth e f f i c i e n c i e s (K^) are shown i n F i g . 18.  The  values of K„ show a general decrease with increasing body weight.  66  Figure 14.  Growth i n dry weight at 10 and 20° C (24%,). Enteromorpha i n t e s t i n a l i s . Fig. 9 (see Fig. 7). 1 mg.  x, males;  Food:  Data converted from data i n  The minimum size of adults i s ca.  +, females;  , 10° C;  20° C.  t  ,  (SLYi)  1H3I3M AcdQ  68  F i g u r e 15.  Growth r a t e v s . body weight a t 10 and 20° C (24%o). Food:  Enteromorpha  intestinalis.  Rates were c a l c u -  l a t e d from the d a t a shown i n F i g . 14. growth r a t e i n mg 15b:  F i g . 15a:  C/day v s . d r y body weight.  Fig.  growth r a t e as a p e r c e n t a g e of the t o t a l body  C/day v s . d r y body weight, , 10° C;  x, males;  , 20° C.  +, females;  69  o-oel  >< •  o-osi  u O-CKi UJ h<  o.oai  i o  01 in  o-cel  coil  ocol •RY  IB •  >< • u • D  '  WEIGHT  CMG)  b  IB.  IE. 10-  m uJ  e-  h< a:  x i— D  a: iD  2-i  X"'  4. •RY  WEIGHT  (MG)  70  Figure 16.  Oxygen uptake vs. body weight at 10 and 20° C (24%o). Rates were calculated from data i n Appendix C.  Males  and females of the same size were assumed to show similar rates.  F i g . 16a:  vs. dry body weight.  oxygen uptake i n mg C/day  F i g . 16b:  oxygen uptake as a  percentage of the.total body G/day vs. dry body weight, x, males;  +, females;  , 10° C;  , 20° C.  71  0*50. 0  lai  0 isL ><  0 141  • \ U  ID 2  0-lHl O-lOl o-ooi  z i o-os4. O  0.04L  cool  o. •RY  WEIGHT  (MG)  so. IB.  >< D \ U  >• D CQ ^°  UJ < io_  u  01  IB14. IE. 10. 8-1 B-1 4-1  a  •RY  WEIGHT  (MG)  72  Figure 17.  Assimilated r a t i o n vs. body weight at 10 and 20° C (24%»).  The assimilated r a t i o n was estimated as the  sum of growth (Fig. 15) and metabolism (Fig. 16). F i g . 17a:  assimilated r a t i o n i n mg C/day vs. dry  body weight.  F i g . 17b:  assimilated r a t i o n as a per-  centage of the t o t a l body C/day vs. dry body weight, x, males;  +, females;  , 10° C;  , 2 0 ° C.  •RY  WEIGHT  (MG)  74  Figure 18.  Net growth e f f i c i e n c y and 20° C (24%«).  (K^) vs. dry body weight at 10°  Net growth e f f i c i e n c i e s i n percent  were estimated as the growth rate (Fig. 15) divided by the sum of the growth and metabolic rates (Fig. 17). Food:  Enteromorpha i n t e s t i n a l i s .  females;  , 10° C;  x, males;  , 20° C.  +,  NET  GROWTH  EFFICIENCY  (%)  However, at body weights less than ca. 0.5 mg, there appeared to be an increase i n K  2  with increasing body weight (a K£ vs. weight  curve exhibiting a hump at smaller sizes was found i n Pontogammarus maeoticus;  Soldatova 1970;  showed higher K than 1 mg.  2  2  Males  values than females, e s p e c i a l l y at sizes greater  At 20° C, K  smaller than ca. 3 mg; K  Makarova and Zaika 1971).  2  values were higher than at 10° C for animals animals greater than 3 mg showed higher  values at 10° C. For the time from hatching u n t i l 0.9-1.0 mm head length  (ca. 1 mg dry wt.) i s attained, the o v e r a l l K 2 values were similar i n males and females, and higher at 20° C (males, 50%; 45%) than at 10° C (males, 39%;  females, 40%).  females,  The maximum K  2  values shown were 46-47% at 10° C (at 0.6-0.8 mg dry wt.) and 51-53% at 20° C (at 0.02-0.05 mg). If the assimilation e f f i c i e n c i e s obtained for 5 mg adults also apply to smaller individuals, then gross growth e f f i c i e n c i e s KKj) could be estimated as 30-31% at 10° C and 30-34% at 20° C (assuming assimilation e f f i c i e n c i e s of 77% at 10° C and 67% at 20° C) f o r growth up to 0.9-1.0 mm head length on Enteromorpha.  V.  DISCUSSION  A.  FACTORS AFFECTING DISTRIBUTION A. pugettensis was found i n the middle and lower i n t e r t i d a l  zones i n tidepools, seaweed clumps, and Zostera beds.  The amphi-  pods were also found subtidally i n seaweeds i n the trap.  The  temperature tolerances of A. pugettensis were more than adequate for survival i n the temperature range recorded i n the middle and  lower i n t e r t i d a l zones at Crescent Beach during sampling times i n t h i s study.  Temperatures outside the recorded range can occur i n  t h i s area:.: temperatures greater than the 24 h high temperature tolerance (24-27° C) can occur i n summer, but infrequently, and for only a short part of the day (during a daytime low t i d e ) ;  tide-  pool temperatures of 0°Ccor less can occur i n winter, and freezing of tidepools r a r e l y occurs (see Husted 1969).  The wide tolerance  range (tolerance to freezing was not examined) plus the a b i l i t y to adjust this range according to the acclimation temperature indicate that temperature w i l l rarely cause mortality i n the middle i n t e r t i d a l zone and deeper.  However, temperature may be a reason f o r  the absence of A. pugettensis from the high i n t e r t i d a l zone at low tide.  In t h i s zone, the duration of low tide exposure i s longer.  As a result, exposure to temperature extremes (including freezing conditions) w i l l be greater than i n lower regions of the beach. Avoidance of desiccation may be another reason f o r the absence from the higher i n t e r t i d a l zone at low t i d e .  Desiccation could  be avoided during a low tide i n t e r t i d a l l y i n tidepools or i n moist a i r within seaweed clumps.  In the high i n t e r t i d a l zone, tidepools  were absent, and seaweed clumps may become dried out (and uninhabitable) as a result of the longer exposure time, especially i n summer temperatures (these clumps were mostly absent i n winter). The 24 h s a l i n i t y tolerance range was much wider than the range of recorded f i e l d s a l i n i t i e s . was ca.  The one week low s a l i n i t y tolerance  ll%o(Chang and Parsons 1975).  S a l i n i t i e s outside the  recorded range may occur as a result of evaporation i n tidepools i n summer, or p r e c i p i t a t i o n , but these s a l i n i t i e s should rarely  78  be of a magnitude or duration that would cause m o r t a l i t i e s . tolerance to low s a l i n i t i e s may  The i n -  l i m i t A. pugettensis to outer es-  tuarine areas where s a l i n i t i e s are higher.  This probably acts i n  combination with competition from species that are adapted to lower s a l i n i t i e s . relatively  In other areas, A. pugettensis i s found i n  high s a l i n i t i e s ;  on the west coast of Vancouver Island,  and i n Porpoise Harbor near Prince Rupert, t h i s species i s found in s a l i n i t i e s of 27-32% (Bousfield 1958; 0  Waldichuk and Bousfield  1962). Oxygen l e v e l s at Crescent Beach were not measured.  In similar  shallow marine environments, low oxygen or anoxic conditions frequently occur (Broekhuysen 1935;  Wieser and Kanwisher 1959).  tory, most adults survived less than 3 h i n anoxia.  In the laboraA l l were  paralyzed during anoxia, and some became paralyzed at oxygen l e v e l s as high as 28% saturation. The survival time i n anoxia i s similar to that of Gammarus oceanicus, although t h i s l a t t e r  species remains  active i n anoxic conditions u n t i l just before death (Wieser Kanwisher 1959).  and  In cultures, ovigerous female A. pugettensis  beat their pleopods more frequently than did other i n d i v i d u a l s , indicating a greater oxygen need by embryos. Wieser and Kanwisher (1959) note that highly mobile  animals,  such as amphipods, do not need.a high tolerance of anoxic conditions because of their a b i l i t y to detect and avoid such areas.  This  a b i l i t y has been shown i n Gammarus oceanicus and G. pulex (Cook and Boyd 1965; ability;  Costa 1966).  A. pugettensis appears to have a similar  much a c t i v i t y was  shown just after sodium s u l f i t e was added  to the medium, indicating an avoidance reaction to low oxygen (or to sodium s u l f i t e ) ;  i n laboratory cultures i n which the medium had  79  become fouled, some individuals were found above the water  surface  on the walls of the culture dishes, i n d i c a t i n g an attempt to avoid the fouled waters (this behavior was  not seen i n normal c u l t u r e s ) ;  in the polluted waters of Porpoise Harbor, A. pugettensis occurred mainly i n bottom waters where oxygen l e v e l s were greater than 30% saturation, and mostly avoided.the near-surface waters where oxygen l e v e l s were l e s s than 10% saturation (Waldichuk and Bousfield 1962). Animals can only exist where food of adequate quality and quantity i s available.  Because of the broad d i e t , and a b i l i t y to  survive several days without food, A. pugettensis may wide v a r i e t y of food environments. distribution. seaweeds;  inhabit a  However, food can s t i l l a f f e c t  The amphipods.were not found i n tidepools without  they were scarce i n t e r t i d a l l y when seaweed clumps  than Chondria? which was seaweeds were absent;  (other  not acceptable as food) and tidepools with  they were abundand i n seaweeds in the subtidal  trap on some days when seaweeds and amphipods were scarce  intertidally;  they were scarce i n the subtidal trap when i t contained no seaweeds. This association of amphipods with seaweeds thus appears to be related to food (as well as to dessication and the a t t r a c t i o n of amphipods to s o l i d  surfaces).  In summary, food, temperature, dessication, s a l i n i t y , and oxygen are important factors a f f e c t i n g d i s t r i b u t i o n .  The wide tolerances  and broad diet allow the species to be widely d i s t r i b u t e d .  B.  FACTORS AFFECTING PRODUCTIVITY Within the tolerated environment, fluctuations i n physical factors  can a f f e c t productivity.  Changes i n s a l i n i t y within the range 12-24%©  80  did not seem important.  In the laboratory, short- or long-term  s a l i n i t y changes i n t h i s range had no effect on oxygen consumption, and long-term exposure to d i f f e r e n t s a l i n i t i e s did not affect growth. Large seasonal changes i n s a l i n i t y were not recorded at Crescent Beach. There may be large d i e l fluctuations i n oxygen l e v e l s i n shallow coastal waters (Broekhuysen 1 9 3 5 ) .  Short-term changes i n oxygen  l e v e l s a f f e c t oxygen consumption, with uptake decreasing as oxygen l e v e l s decrease.  A similar pattern i s reported i n some other  coastal-water crustaceans, while others=are able to maintain constant oxygen uptake over a wide range of oxygen l e v e l s (van Weel et a l . Walshe-Maetz 1 9 5 6 ;  1954;  Vernberg 1 9 7 2 ) .  There may be smaller  seasonal changes i n oxygen l e v e l s (e.g. see Bawden et a l . 1 9 7 3 ) . The e f f e c t s of such long-term changes i n oxygen l e v e l s on productivity were not examined, although there were lower oxygen l e v e l s at 2 0 ° C than at 1 0 ° C i n laboratory experiments (colder water has a higher oxygen carrying-capacity). Temperature i s the most important physical factor a f f e c t i n g production.  Large seasonal and d i e l fluctuations i n temperature  do occur, and temperature does a f f e c t production. to 1 0 or 2 0 ° C had Q^Q 20° C.  Animals acclimated  values of 1.2-1.3 f o r oxygen uptake at 10 and  These low values indicate an adaptation to a variable tempera-  ture environment;  various invertebrates adapted to the less v a r i a b l e  pelagic environment have Q-^Q values of .1.6-3.6 (Ikeda 1 9 7 0 ; 1970).  Kinne  Warm-acclimated. A. pugettensis maintained low Q-^Q values up  to 2 5 ° C (which i s near the maximum that would be experienced). The high Q-^Q values at low test temperatures would probably be lower i n  81  animals acclimated to winter temperatures, since i t i s only during winter that near-zero temperatures occur. Growth rates up to adult size, including embryonic rates, were much higher at 20° C than at 10° C.  development  The large  tempera-  ture effect on growth and small effect on metabolism r e s u l t i n much higher growth e f f i c i e n c i e s (up to adult size) at 20° C. Data from f i e l d samples indicated other e f f e c t s of temperature on growth.  In warmer months, the minimum, mean, and maximum sizes  of mature animals were smaller than i n colder months.  A temperature  effect on maximum size was also indicated i n laboratory experiments. Animals larger than ca. 3.5 mgg had higher growth rates, and appeared to have longer l i f e spans, at 10° C than at 20° C. in a larger f i n a l size at lower temperatures.  This should r e s u l t  Similar temperature  e f f e c t s on incubation period, growth rate to maturity, maximum s i z e , and l i f e span have been reported i n many marine invertebrates (see Kinne 1970). Because brood size increased with female size, average brood sizes were smallest i n July, when females were smallest.  Winfer  females did not have the largest average brood sizes, despite the large female sizes, because of the r e l a t i v e l y small broods i n the largest (>1.5mmm head length) females.  The largest average brood  sizes were i n June, when females were r e l a t i v e l y large, and average brood sizes were larger at a l l female sizes than i n other months. From August to early October, the numbers of reproductive females collected were i n s u f f i c i e n t to allow determination of their reproductive capacity.  Young animals were present i n these months  (1973), indicating that reproduction was occurring.  The s c a r c i t y  82  of adults i n i n t e r t i d a l c o l l e c t i o n s i n these months appeared to be due to the s c a r c i t y of suitable habitats (the beach was covered with Chondria);  more adults may have been recovered i f subtidal c o l l e c -  tions had been made i n these months. The shorter incubation time, faster growth of young, and the smaller size at maturity, result i n a p o t e n t i a l l y greater frequency of broods i n warmer months.  This, combined with the large broods  i n June, means that the greatest productivity should occur i n t h i s month.  In the warmest months, July and August, the effect of small  broods r e s u l t i n g from small female size should be overcome by an increased frequency of broods at the higher temperatures;  productivity  should be higher than i n colder months. Temperature also a f f e c t s feeding.  The assimilated r a t i o n per  i n d i v i d u a l (as estimated from the sum of growth and metabolism) was higher at 20° C than at 10° C, and the assimilation e f f i c i e n c y was lower.  Therefore the t o t a l r a t i o n must be higher at 20° C.  Also, the smaller size of animals i n warmer months r e s u l t s i n a higher weight-specific r a t i o n than for animals i n colder months. These factors, combined with the greater productivity of the popul a t i o n i n warmer months w i l l r e s u l t i n a larger food consumption (by the population) than i n colder months. The quantity of available food a f f e c t s productivity.  With reduced  food supplies, growth and metabolism must be reduced, and therefore productivity i s reduced. also be reduced.  Below a c e r t a i n food l e v e l , survival w i l l  Quantity of available food should be greatest  i n warm months, when primary production i s greatest. The type of food also a f f e c t s growth and s u r v i v a l .  The a b i l i t y  to ingest foods depends upon the texture of foods.  Plants with  firm textures cannot be eaten, but after decay they may become acceptable.  soften and  A similar e f f e c t of texture on food accepta-  b i l i t y occurs i n Marinogammarus (Martin 1966).  The decay of plant  tissue i s accompanied by increased colonization of microorganisms which may  increase the n u t r i t i o n a l value of the food as well as  causing further decay.  The size of food was also a factor.  The  feeding apparatus of A. pugettensis can handle pieces of seaweeds or animal foods and clumps of diatoms, but i s l e s s able to handle f i n e , loose d e t r i t u s .  Amphipods fed animal foods alone did not show  as high growth and survival rates as did those fed both animal and plant foods or certain plant foods alone.  A need for plant food  for maximum growth and survival also occurs i n Gammarus duebeni (Kinne 1959). No quantitative measurements were made of the food supply for A. pugettensis at Crescent Beach.  Zostera was the most common  macrophyte, but i n the laboratory, dead strands of t h i s plant were not eaten by young, and only occasionally by adults. a more advanced state of decay may be acceptable.  Strands i n  Enteromorpha,  the next most abundant macrophyte, allowed high growth and i n the laboratory.  It was present i n the f i e l d  survival  (mainly spring and  summer), but the standing stock was never large, possibly because of grazing by amphipods.  Chondria was present i n large quantities  for a short part of the year, but was not eaten. were not common.  Other macrophytes  Clumps of benthic diatoms resulted i n high growth  and survival rates i n the laboratory; covered much of the mud  a thin layer of diatoms often  at Crescent Beach (although they were not  84  the same species as those i n the laboratory). Diatoms may be  important,  with bacteria and other microorganisms, as epiphytic material which can be grazed o f f Zostera or ingested along with Enteromorpha.  In coastal  environments, epiphytes are important food sources f o r invertebrates including amphipods (Barnard 1969;  Odum 1971).  Flesh from dead  and some l i v e animals can be eaten, especially by adults; a v a i l a b i l i t y of animal food.is unknown. u t i l i z e d to some extent.  The abundant d e t r i t u s may  be  The broad diet and the a b i l i t y to survive  several days without food, mean that food requirements are e a s i l y met.  the  f o r survival  However, because of the effect of food type and  quantity on growth and s u r v i v a l , productivity i s affected by food. In summary, temperature and food are the most important a f f e c t i n g productivity.  Warmer temperatures  greater frequency of reproduction. larger i n warm months.  factors  allow faster growth and  Food supply should also be  Therefore, productivity should be highest i n  warmer months.  C.  PRODUCTIVITY OF ANISOGAMMARUS PUGETTENSIS Productivity depends on growth and reproduction.  Net growth  e f f i c i e n c i e s were calculated from data on metabolism and growth. Oxygen consumption by A. pugettensis i s i n the range of values shown by other amphipod species (see Ivanova 1972;  for comparison, wet  weight of A. pugettensis i s ca. 4 times the dry weight).  Growth  rates of A. pugettensis are higher than that shown by many A t l a n t i c amphipods.  The 28-35 days at 20° C and 49-63 days at 10° C required  by A. pugettensis to a t t a i n the minimum adult size compares with 130 days at 15° C for Marinogammarus marinus (Vlasblom 1969)  and 150-180  85  days at 18-20° C for Gammarus duebeni (Kinne 1959).  G. zaddachi and  G. salinus show s l i g h t l y higher rates (ca. 25 days at 19-20° C; 1960,  1961)  than A. pugettensis.  Kinne  Calculated net growth e f f i c i e n c i e s  for growth of A. pugettensis to maturity on Enteromorpha are above average compared to values for other aquatic organisms (see Sushchenya 1970;  Winberg 1971). Gross growth e f f i c i e n c i e s were calculated from assimilation  and net growth e f f i c i e n c i e s .  A s s i m i l a t i o n e f f i c i e n c i e s for 5 mg  adult A. pugettensis feeding.on Enteromorpha (measured by ^ C Conover methods) and on benghic diatoms (-^C  and  method) were high,  as other authors (using various methods) have found for benthic amphipods feeding on similar foods (Table VII). probably underestimated  The Conover method  the assimilation e f f i c i e n c y of benthic  diatoms by A. pugettensis because of the assumption that the ash f r a c t i o n of food i s not assimilated; (Tsikhon-Lukanina  et a l . 1968;  t h i s assumption appears i n v a l i d  Forster and Gabbott 1971).  t h i s method w i l l understimate assimilation e f f i c i e n c y ,  Therefore  especially  i n foods with high ash contents such as the benthic diatom  mixture  (ash was 45% of dry weight;  Assimila-  i n Enteromorpha ash was 18%).  tion e f f i c i e n c i e s of A. pugettensis feeding on animal f l e s h were not measured, but the scarcity of f e c a l p e l l e t s when feeding on f l e s h indicated higher e f f i c i e n c i e s than with plant foods.  In other marine  Crustacea, assimilation e f f i c i e n c i e s of 90% or more occur with animal food (Tsikhon-Lukanina  et a l . 1968;  Ivleva 1970).  In this study, assimilation e f f i c i e n c i e s were measured only i n adults averaging 5 mg dry weight.  Larger (10 mg) A. pugettensis  have a lower assimilation e f f i c i e n c y  (Table VII).  Data from other  amphipods (Table VII) indicate that young should have assimilation  Table VII.  Assimilation efficiencies  Temp. (C)  A (%)  Method  Reference  24 24  77 67  "^C and Conover l^C and Conover  present study  10  28  59  14r  Chang and Parsons 1975  11  23  75  Pontogammarus maeoticus (1 mg)  22-24  14  85-90  dry wt. & nitrogen of food & feces  Karpevich 1946  Pontogammarus maeoticus j uv. 0. 9 mg adults 9 mg  2h 24 24  12 12  81 76-81  c a l o r i f i c value of food & feces  Soldatova et a l . 1969  24 24  12 12  61 64  c a l o r i f i c value of food & feces  Soldatova et a l . 1969  Food  Amphipod  Enteromorpha intestinalis  Anisogammarus pugettensis (5 mg adults)  10 20  Enteromorpha intestinalis  Anisogammarus pugettensis (10 mg)  Enteromorpha sp.  Anisogammarus pugettensis (old juveniles)  Enteromorpha sp.  Cladophora (live)  Cladophora (dead)  (A) of plant foods by benthic amphipods.  Pontogammarus maeoticus juv. 0.8 mg adults 6 mg  Sal. (%„)  1 4  C - C r dual l a b e l 5 1  W.A. Heath, unpubl.  oo ON  Table VII.  Continued  Food  Amphipod  Cystoseira  Orchestia bottae young adults  Temp. (C)  Sal. A (% ) (%)  Method  Reference  ST* ST  50 32  not given not given  Suschenya 1970  C Conover  present study  a  clumps of benthic diatoms (Nitzschia sp.)  Anisogammarus pugettensis (5 mg adults)  10 10  24 24  82 46  1 4  Skeletonema costatum on f i l t e r paper  Anisogammarus pugettensis (old juveniles)  11  23  90  1 4  C- Cr  Navicula sp. in sediment  H y a l e l l a azteca (0.6-0.8 mg)  15  75  1 4  C  epiphytes on Chara sp. (17% ash)  H y a l e l l a azteca (0.6-0.8 mg)  15 15 15  72 73 80  gravimetric Conover protein content of food & feces  * ST = s e m i - t e r r e s t r i a l ** FW = freshwater  FW FW FW  5 1  dual l a b e l  W.A. Heath, unpubl. Hargrave 1970 Hargrave ' 1970  e f f i c i e n c i e s equal to, or greater than, adults.  If assimilation  e f f i c i e n c i e s of young are assumed equal to 5 mg adults, then the estimated gross growth e f f i c i e n c i e s for growth of A. pugettensis to 1 mg on Enteromorpha are above average compared to values obtained for various Crustacea (see Sushchenya 1970). Makarova and Zaika (1971) note that growth e f f i c i e n c i e s have been calculated by d i f f e r e n t formulas that are not s t r i c t l y comparable;  e.g. net growth e f f i c i e n c i e s calculated as K 2 = G/G+T  are not equal to estimates using K/? = G/AR  (where G i s the growth  rate, T i s the oxygen uptake rate, A i s the assimilation e f f i c i e n c y , and R i s the r a t i o n ) , since G+T underestimates AR by the amount of energy l o s t i n molting, excretion, and production of young. Therefore, K 2 estimates using the former formula (as i n the present study) may be greater than estimates using the l a t t e r formula. It was o r i g i n a l l y planned to estimate the r a t i o n also from the measurements of assimilation e f f i c i e n c y and egestion rates. egestion rates were too variable to be of use for t h i s  However,  purpose.  Many of the animals showed egestion rates much higher than would be expected on the basis of the values of assimilation e f f i c i e n c y , growth, and metabolism, while other individuals did not feed during the test period.  To overcome t h i s v a r i a b i l i t y i n feeding rates,  f e c a l p e l l e t s should be collected d a i l y for several days i n succession, and averaged over the period. Soldatova (1970) estimated that the energy expenditure i n molting i n Pontogammarus maeoticus was 18% of the weight increase f o r younger animals, and higher i n older animals;  over the entire l i f e  span, 8% of the t o t a l assimilated energy was used i n molting, 5% i n  89  weight gain, and 87% i n metabolism.  Mathias (1971) estimated the  energy of molting to be 40% of. the energy of growth, or 8% of the t o t a l assimilated energy, i n a population of Hyalella azteca. rates of A. pugettensis were not d i r e c t l y measured.  Molting  Molting rates  of adult females could be estimated from the incubation period, since molting occurred just before ovulation, and just after the hatching of young;  t h i s was. also found for H. azteca (Mathias 1971).  This would mean a molt i n t e r v a l of about 10 days at 20° C and 15-17 days at 10° C for adult female A. pugettensis.  Molt i n t e r v a l s f o r  younger animals are probably shorter (see Kinne 1959; Vlasblom 1969) . If i t i s assumed that ca. 9 molts are required for A. pugettensis to reach 0.9-1.0 mm head length (1 mg), i f each molt i s 10-20% of the dry body weight at the time of molting for larger animals and a larger percentage of smaller animals (see Mathias 1971;  Ivleva  1970) , and i f the c a l o r i f i c value (or carbon content) per dry weight of molts i s 1/3-1/2 that of dry body tissue (see Soldatova 1970; Mathias 1971), then the energy value of molts during growth to maturity would be 10-30% of the weight gain. pugettensis (and other amphipods;  However, because A.  Martin 1966; Barnard 1969)  usually ingest each molt a f t e r molting, not a l l of the energy value of the molts i s l o s t .  As a r e s u l t , the effect of neglecting the  energy loss i n molting i n the estimation of assimilated r a t i o n and growth e f f i c i e n c i e s should not be important i n the period of rapid growth up to maturity.  For large animals, the energy value of molts  becomes equal to or greater than the energy gain i n growth, and assimilated rations w i l l be s i g n i f i c a n t l y underestimated (growth  90  e f f i c i e n c y w i l l be overestimated) i f molting i s ignored. Energy losses due to the excretion of soluble organic substances were not measured for A. pugettensis.  Excretion i s usually considered  to be n e g l i g i b l e r e l a t i v e to the energy of oxygen consumption (e.g. Soldatova 1970;  Sushchenya 1970).  If t h i s i s true, then the error  i n the growth e f f i c i e n c y estimates due to the omission of t h i s energy loss would not be great.  However, Hargrave (1971) found  the energy of excretion to be of the same order of magnitude as that of oxygen consumption i n H y a l e l l a azteca. No young were produced study.  Therefore,  i n the growth experiments of the present  values f o r adultsfemales are not representative  of reproducing adults.  If production of young i s considered an  energy l o s s , then K/> values for reproducing females would be lower than i n the present study.  If production of young i s considered  as part of growth, then 10? values for reproducing females should be similar to, or possibly higher than, values for males (cf. F i g . 18). The brood sizes of A. pugettensis (average 30-88) were larger than those of most A t l a n t i c amphipods (e.g. Sexton 1928; Kinne 1959, 1960, 1969);  1961;  Cheng 1942;  Steele and Steele 1969, 1970, 1972;  Vlasblom  larger broods (average 140-150) were found i n Gammarus locusta  (Sexton 1928).  As i n other species, brood size increased as female  size increased.  There were indications of a decrease i n brood  i n the largest female A. pugettensis.  size  This occurs i n some species of  Gammarus, and can be attributed to s e n i l i t y i n older (larger) females (Cheng 1942;  Kinne 1961).  If the dry weight of newly hatched A.  pugettensis i s estimated as 0.009 mg  (extrapolated from F i g . 7), then  each brood represents an average of 12-20% of female  weight.  91  The reproductive capacity depends on the frequency of broods as well as on brood size.  One factor a f f e c t i n g frequency of broods  i s the length of the incubation period.  The 9-10 days at 20° C  and 14-16 days at 10° C for A. pugettensis was shorter than that found for many species of amphipods (see Thurston 1970);  e.g.  G. duebeni required 12.5 days at 20° C and 29 days at 10° C (Kinne 1959).  The incubation time for A. pugettensis was about the same  as that shown by Marinogammarus marinus (Vlasblom 1969) and G_. ' salinus (Kinne 1960). If female A. pugettensis ovulated at each molt, then a brood could be produced about every 10-11 days at 20° C and every 15-17 days at 10° C, with broods becoming successively larger i n any one female (except i n the largest females).  Hynes (1955) states that  most amphipods are capable of producing several broods i n succession, one at each molt, although an occasional brood may be missed (Sexton 1928).  However, 28-90 days (mean, 50) separate successive ovulations  of Marinogammarus marinus at 15° C (this i s greater than the average length of one molt cycle;  Vlasblom 1969).  S u f f i c i e n t data were not  obtained to allow estimation of the average time between successive broods i n female A. pugettensis. In the laboratory, one female, had 3 successive broods ( i n 3 molt c y c l e s ) , while other females did not mate before the end of a molt cycle i n which a brood was developing, so that at least one molt cycle would occur before the next ovulation. In f i e l d c o l l e c t i o n s , some females were observed to be i n precopula while already carrying a brood, i n d i c a t i n g that another ovulation would occur at the next molt.  The great majority of the larger females  i n the f i e l d samples were ovigerous.  It appears that broods at  successive molts occur i n natural conditions, but a resting i n t e r v a l of at least one molt cycle between broods i s probably not uncommon. F i e l d data indicate that reproduction occurs throughout the year at Crescent Beach, since either reproductive females or young are present i n a l l months.  Many A t l a n t i c amphipods show a resting  stage (not due to temperature), during which no reproduction occurs, at some part of the year (Steele 1967).  However, other species,  such as Gammarus chevreuxi and Marinogammarus marinus reproduce throughout  the year (Sexton 1928.;  Vlasblom 1969).  In summary, A. pugettensis shows a large brood s i z e , probably a high frequency of broods, reproduction throughout growth rates, and high growth e f f i c i e n c i e s .  the year, high  This should r e s u l t i n  a large, highly productive population, e s p e c i a l l y i n warmer months when growth rates, brood frequency, and food supplies should be highest. This p o t e n t i a l l y high productivity, combined with the broad d i e t , indicates an important* r o l e for A. pugettensis as a consumer i n higher s a l i n i t y estuarine environments.  The amphipod i s probably  an important prey species for various f i s h e s , although no studies of predation on A. pugettensis were done.  Sculpins and blennies,  which are known to eat amphipods i n shallow coastal waters (e.g. Husted 1969; B. Leaman, personal communication), are present at Crescent Beach.  In Mamquam Channel i n the Squamish estuary, large  numbers of A. pugettensis are eaten by juvenile salmon (Levings 1973) .  D.  IMPORTANCE TO MARICULTURE An object of t h i s study was to determine the s u i t a b i l i t y of  93  A. pugettensis i n a salmon mariculture impoundment.  The data indicate  that many of the q u a l i t i e s wanted for an organism i n an impoundment food chain are shown by t h i s species.  The tolerances to physical  factors were wide, and should be s u f f i c i e n t to survive f l u c t u a t i o n s i n impoundment conditions.  Productivity should be high.  Reproduction  should occur throughout the year i n the impoundment.  The broad  d i e t can mean a large food supply for the amphipods.  In a shallow  a r t i f i c i a l upwelling impoundment, such as that suggested by Brown and Parsons (1972) , a dense layer of pihy.t'ddetr.±bus (clumps of phytoplankton that has sunk to the bottom, b a c t e r i a , and organic slimes) i s produced.  In the present study (also W.A.  Heath, personal  communication), A. pugettensis could u t i l i z e similar foods  (clumps  of diatoms) with high a s s i m i l a t i o n e f f i c i e n c i e s and high growth rates.  The amphipods could also eat dead or disabled f i s h ,  thus  preventing d e t e r i o r a t i o n of water conditions, while obtaining food. An essential requirement  for successful mariculture i s that  the cultured f i s h show high growth rates when feeding on the amphipod. This was not examined i n the present study.  As noted above, A.  pugettensis i s an important part of the diet of j u v e n i l e salmon feeding i n the Mamquam Channel.  In preliminary experiments, j u v e n i l e  sockeye and coho salmon fed on a diet of frozen A. pugettensis for at l e a s t 2 weeks.  Some growth was shown, but longer-term experiments  would be needed to v e r i f y the s u i t a b i l i t y of A. pugettensis as food. In freshwater environments, salmonids can grow on similar amphipod species.  Surber  (1935) raised rainbow and brook trout f i n g e r l i n g s  (ca. 20 g wet weight) up to 100 g size i n 5 months time, with l i v e Gammarus fasciatus (average dry weight 3.3 mg each) as the sole food.  The conversion rate of dry weight of food to wet weight of f i s h was a high 1.2, and the f i s h showed better c o l o r a t i o n than was normally found i n hatchery and wild populations.  If similar r e s u l t s can be  shown for marine or estuarine amphipods and anadromous salmonids then amphipod-salmonid impoundment mariculture should be f e a s i b l e .  95  VI.  LITERATURE CITED  Barnard, J.L. 1954. Marine Amphipoda of Oregon. Oregon State Monographs, Studies i n Zoology, No. 8_. Oregon State College, C o r v a l l i s , 103 p. ______  1969. The families and genera of marine gammaridean Amphipoda. B u l l . U.S. Nat. Mus. No. 271, 535 p.  Bawden, C A . , W.A. Heath, and A.B. Norton. 1973. A preliminary baseline study of Roberts and Sturgeon Banks. Westwater Research Centre (Univ. B r i t i s h Columbia, Vancouver) Tech. Rep. No. 1_, 54 p. :  Bousfield, E.L. 1958. Ecological investigations on shore invertebrates of the P a c i f i c coast of Canada, 1955. Nat. Mus. Can. B u l l . No. 147: 104-115. Broekhuysen, G.J., J r . 1935. The extremes i n percentages of dissolved oxygen to which the fauna of a Zostera f i e l d i n the tide zone at Nieuwediep can be exposed. Arch. Neerl. Zool. 1_: 339-346. Brown, P.S. and T.R. Parsons. 1972. The effect of simulated upwelling on the maximization of primary productivity and the formation of phytodetritus. Mem. I s t . I t a l . Idrobiol. , 2_9 Suppl.: 169-183. Chang, B.D. and T.R. Parsons. 1975. Metabolic studies on the amphipod Anisogammarus pugettensis i n r e l a t i o n to i t s trophic position i n the food web of young salmonids. J . Fish. Res. Bd. Can. 32: 243-247. Cheng, C. 1942. On the fecundity of some gammarids. Ass. U.K. 2_5: 467-475.  J . Mar. B i o l .  Conover, R.J. 1966. Assimilation of organic matter by zoology. Limnol. Oceanogr. 11_: 338-345. Cook, R.H. and CM. Boyd. 1965. The avoidance by Gammarus oceanicus Segerstrale (Amphipoda, Crustacea) of anoxic regions. Can. J . Zool. 43: 971-975. Costa, H.H. 1966. Response of Gammarus pulex (L.) to modified environment. I I I . Reactions to low oxygen tensions. Crustaceana 11: 175-189. Forster, J.R.M. and P.A. Gabbott. 1971. The assimilation of nutrients from compounded d i e t s by the prawns Palaemon serratus and Pandulus platyceros. J . Mar. B i o l . Ass. U.K. 51: 943-961. . .Goodman, D. and P.R. Vroom. 1972. Investigations into f i s h u t i l i z a t i o n of the inner estuary of the Squamish River. Fisheries Service (Vancouver) Tech. Rep. No. 1972-12, 52 p.  Harger, J.R.E. and M.D. Nassich.uk. 1974. Marine i n t e r t i d a l community responses to kraft pulp m i l l effluent. Water A i r S o i l P o l l u . 3_: 107-122. Hargrave, B.T. 1970. The u t i l i z a t i o n of benthic microflora by Hyalella azteca (Amphipoda) . J . Anim. Ecol. 39_: 421-437. . 1971. An energy budget for a deposit-feeding amphipod. Limnol. Oceanogr. 16: 99-103. Hynes, H.B.N. 1955. The reproductive cycle of some B r i t i s h freshwater Gammaridae. J. Mar. B i o l . Ass. U.K. 24_: 352=387. Husted, L.D. 1969. E f f e c t s of predation on d i s t r i b u t i o n of the amphipod, Maera dubia. B.Sc. Thesis, Dept. of Zool., Univ. of B r i t i s h Columbia, Vancouver, 34 p. Ikeda, T. 1970. Relationship between r e s p i r a t i o n rate and body size i n marine plankton animals as a function of the temperature of habitat. B u l l . Fac. Fish., Hokkaido Univ. 21: 91-112. Ivanova, M.B. 1972. The influence of temperature on the oxygen consumption by Gammaracanthus l a c u s t r i s Sars (Amphipoda). Pol. Arch. Hydrobiol. 19: 319-324. Ivleva, I.B. 1970. The influence of temperature on the transformat i o n of matter i n marine invertebrates, p. 96-112. In J.H. Steele (ed.) Marine food chains. Univ. C a l i f . Press, Berkeley and Los Angeles. Karpevich, A.F. 1946. Feeding of Pontogammarus maeoticus i n the Caspian Sea. (In Russian; summary i n English) Zool. Zh. 25: 517-522. Kinne, 0. 1959. Ecological data on the amphipod Gammarus duebeni. A monograph. Veroff. Inst. Meeresforsch. Bremerh. 6_: 172-202. . 1960. Gammarus salinus - einige Daten uber den Umwelteinfluss auf Wachstum, Hautungsfolge, Herzfrequenz und Eientwicklungsdauer. (Summary i n English) Crustaceana 1_: 208-217. . 1961. Growth, molting frequency, heart beat, number of eggs, and incubation time i n Gammarus zaddachi exposed to d i f f e r e n t environments. Crustaceana 2_: 26-36. . 1970. Temperature. Animals. Invertebrates, p. 407-514. In 0. Kinne (ed.) Marine ecology, v o l . 1(1). Wiley-Interscience, London. Levings, C D . 1973. I n t e r t i d a l benthos of the Squamish estuary. Fish. Res. Bd. Can. (Pac. Envir. Inst.) MS Rep. No. 1218: 60 pp.  97  Light, S.F., R.I. Smith, F.A. P i t e l k a , D.P. Abbott, and F.M. Weesner. 1954. I n t e r t i d a l invertebrates of the central C a l i f o r n i a coast. Univ. C a l i f . Press, Berkeley and Los Angeles, 446 p. Makarova, N.P. and V.Ye. Zaika. 1971. Relationship between animal growth.and quantity of assimilated, food. Hydrobiol. J . 7/3): 1-8. Martin, A.L. 1966. Feeding and digestion i n two i n t e r t i d a l gammarids: Marinogammarus obtusatus and M. ' p i r l o t i . J . Zool. 148: 515-525. Mathias, J.A. 1971. Energy flow and secondary production of the amphipods. Hyalella. azfceea and Crangonyx richmondensis. occidentalis i n Marion Lake, B r i t i s h Columbia. J . Fish. Res. Bd. Can. 28: 711-726. Odum, E.P. 1971. Fundamentals of ecology, 3rd ed. W.B. Philadelphia, 574 p.  Saunders,  Parsons, T.R. and M. Takahashi. 1973. B i o l o g i c a l oceanographic processes. Pergamon Press, Oxford, 186 p. Powers, J.E. 1973. Dynamics of a salmon culture pond. Today 18_:. 69-72. (In Simulation 21(4))  Simulation  Sexton, E.W. 1928. On the rearing and, breeding of Gammarus i n laboratory conditions. J . Mar. B i o l . Ass. U.K. 15_: 33-55. Soldatova, I.N. 1970. The energy balance of the amphipod Pontogammarus maeoticaus. Oceanology 10: 129-138. , Ye.A. Tsikhon-Lukanina,. G.G. Nikolayeva and T.A. Lukasheva. 1969. The conversion of-food energy by marine crustaceans. Oceanology 9_: 875-882. Steele, D.H. and V.J. Steele. 1969. The biology .of Gammarus (Crustacea, Amphipoda) in.the northwestern A t l a n t i c . I. Gammarus duebeni L i l l j . Can. J . Zool. 47_: 235-244. . 1972. Biology.of Gammarellus angulosus (Crustacea, Amphipoda) - i n the northwestern A t l a n t i c . J . Fish. Res. Bd. Can. 29: 1337-1340. Steele, V.J. 1967. Resting stage i n .the reproductive cycles of Nature 214: 1034. —Gammarus. — — — — i and D.H. Steele. 1970. The biology of Gammarus (Crustacea, Amphipoda) i n the northwestern A t l a n t i c . I I . Gammarus setosus Dementieva. Can. J . Zool. 48_: 659-671. Surber, E.W. 1935. Trout feeding experiments with natural food (Gammarus f a s c i a t u s ) . Trans. Am. F i s h . Soc. 65: 300-304.  98  Sushchenya, L.M; 1970. Food rations, metabolism and growth of crustaceans, p. 127-141. In J.H. Steele (ed.) Marine food chains. Univ. C a l i f . Press, Berkeley and Los Angeles. Teal, J.M. and K. Halcrow. 1962. A technique for measurement of-. r e s p i r a t i o n of single copepods at sea. J.. Conseil 2_7_:" 125-128. Thurston, M.H. 1970. Growth-in Bovallia. gigantea Pfeffer (Crustacea: Amphipoda). p. 269-278. In M.I. Holdgate (ed.) Antarctic ecology, v o l . 1. Academic Press, London. Tsikhon-Lukanina, Ye.A., I.N. Soldatova, and G.G. Nikolayeva. 1968. Food assimilation by bottom crustaceans of the Sea of Azov and methods for i t s determination. Oceanology 8_: 388-394. Vernberg, -F.J. 1972. Dissolved.gases. Animals, p. 1491-1515. _In.O. Kinne (ed.) Marine ecology, v o l . 1(3). Wiley-Interscience, London. Vlasblom, A.G. 1969. A study of. a.population of..Marinogammarus. marinus (Leach) i n the Oosterschelde. Neth. J. Sea Res. 4_: 317-338. Waldichuk, M.,and E.L. Bousfield. .1962. Amphipods i n low-oxygen marine waters adjacent to a.sulphite pulp m i l l . J . Fish. Res. Bd. Can. 19: 1163-1165. Walshe-Maetz, B.M. 1956. Controle r e s p i r a t o i r e et metabolisme chez l e s crustaces. Vie M i l i e u 7_: 523-543. Weel, P.B.van, J.E. Randall., and M.. Takata. .1954. Observations on the oxygen consumption of c e r t a i n marine Crustacea. Pac. Sci. 8_: 209-218. Wieser, W. and J. Kanwisher. 1959. Respiration, and anaerobic survival i n some sea weed-inhabiting invertebrates. B i o l . B u l l . 117: 594-600. Winberg, G.G. (ed.) .197.1.. Methods for -the estimation -of -production of aquatic animals. Academic Press, London, 175 p.  99  APPENDIX A. Data f o r i n d i v i d u a l . f i e l d samples. . Samples were classed according to s i z e , sex, and reproductive state. and habitat data are presented.  Time, temperature, s a l i n i t y ,  100  Appendix A.  Numbers of A. pugettensis i n . f i e l d samples. (T, t o t a l ; M, males; NF, non-reproductive females; RF, ovigerous or mating females; *, subsample)  DatejTime Temp.;Sal. Habitat 1  Head length (mm)  18/V/73;1200 21.9° C;26.3%.Tidepools T  M  NF  0.30-0.49 0.50-0.69 0.70^0.89 0.90-1.09 1.10-1.29 1.30-1.49 1.50-1.69 1.70+  127 36 8 5 2 3 3 2 2 2 1 1 -  Total  182*  Date;Time Temp.;Sal. Habitat Head length (mm)  RF •  1 -  28/Vl/73;0925 21.3° C;21.8%„ Tidepools T  0.30-0.49 0.50-0.69 0.70-0.89 0.90-1.09 1.10-1.29 1.30-1.49 1.50-1.69 1.70+  15 21 3  Total  42  2 1  M  NF  5/Vl/73;1430  19/VI/73;1325 18.3° C;25.1%o Tidepools  Tidepools. T  M  NF  T  RF  75 16 3 1  7 9  95  16  16/VII/73;1155 23,.7° C;25.9% Tidepools 0  RF  T  1 - 1 1 -  10 32 19 9 2 1  73  M  2 1 1  NF  2 -  M  NF  RF  30/VIl/73;1130 21.3° C;27.0% Tidepools o  RF  T  M  NF  3 1 -  7 27 21 31 13 4  9 9 4  8  RF  5 1 3 -  103*  time i s the predicted time of the low tide (Pac. Std. Time) temperature and s a l i n i t y data f o r . i n t e r t i d a l c o l l e c t i o n s are the averages of 2 or more tidepools.  101  30/VII/73;1130 21.30 C;27.0%.  Date;Time Temp.;Sal. Habitat  Seaweeds  Head length (mm)  T  M  NF  27/VIH/73;1030. 11/IX/73;1020 21.70 C;22.7%. 21.7° C;24.5%«  Tidepools RF  T  M  NF  Tidepools  RF.  T  M  NF  RF  0.30-0.49 0.50-0.69 0.70-0.89 0.90-1.09 1.10-1.29 1.30-1.49 1.50-1.69 1.70+  10 8 11 26 6 11 12 11 1 3 3 -  Total  70*  72  79*  Date;Time Temp.;Sal. Habitat  11.50 c Tidepools  9/X/73;0915  23/X/73;0900 13.0°C;26.7%o  22/Xl/73;2205 6.4° C;19.8%.  Head length  (mm)  T  M  NF  7 -  24 33 8 . 3 1 2 2 - 2 3 2 -  1  Tidepools and. Seaweeds RF  0.30-0.49 0.50-0.69 0.70-0.89 0.90-1.09 1.10-1.29 1.30-1.49 1.50-1.69 1.70+  T  M  NF  30 36 22 15 6 4 7 5 1 4 3 2 2 -  RF  1 1 1 -  116*  18 37 14 8 1 1 1 1  2 1  -  -  .Tidepools and. Zostera beds T  M  1 3 20 32 20 10 18 8 5 5  NF  RF  3 3  7 7  -  105*  Total  Few seen  Date;Time Temp.;Sal. Habitat  19/XIl/73;2020 7.3° C;24.8%.  4/ll/74;2135 5.3° C;20.7%,  28/ll/74;1600 8.3° C;25.2%,  Tidepools  Tidepools  Tidepools  Head length (mm)  0.30-0.49 0.50-0.69 0.70-0.89 0.90-1.09 1.10-1.29 1.30-1.49 1.50-1.69 1.70+ Total  T  M  NF  10 4 12 35 35 18 16 15 8 • 3 4 4 2 2 117*  RF  1 4 -  T  M  N'F< RF  16 8 2 3 10 2 3 10 4 1 9 5 9 9 67*  5 5 4 -  T  M  14 15 28 19 3 1 3 2 4 -  11 — 87*  NF  -  RF  2 1 4 1  102  11/III/74;1340 12.3° C;25.3%. Tidepools.  Date;Time Temp.;Sal. Habitat Head length (mm) 0.30-0.49 0.50-0.69 0.70-0.89 0.90-1.09 1.10-1.29 1.30-1.49 1.50-1.69 1.70+  M NF RF  T  no c o l l e c t i o n made; some young and adults seen, including reproductive females  26 31 19 10 6 6 4 1  T  Total  M  NF  25/lV/74;1325 10.9° C;26.0% Tidepools  o  (mm)  T  M  NF  RF  T  M  NF  RF  1 3 2 - 4 1 - 3 1 -  9 23 23 24 15 12 1 2  8 6 1 2  2 1  5 5  2  0.30-0.49 0.50-0.69 0.70-0.89 0.90-1.09 1.10-1.29 1.30-1.49 1.50-1.69 1.70+  o  1 16 36 17 8 3  —  —  109*  25/lV/74;1325 12.0Q C;24.0% Subtidal trap T  9/lV/74;1305 14.7 C;25.5%«Tidepools  RF  103*  Date;Time Temp.;Sal. Habitat Head.length  28/lIl/74;1435 11.0° C;26.3%. Tidepools  M  NF  RF  5 9 9  3 2 7 20 8 7 - 1 3 -  26/lV/74;1410 12.08 C;24.5%. Zostera beds (few i n pools) . T M 4 8 10 17 17 6 5 3  2 8 6 2 3  NF  RF  8 4  3 5  -  1  -  2  -  Total  Few  81*  70*  Date;Time Temp.;Sal. Habitat  8/V/74;1235 17.0° C;25.3%« Seaweeds, some i n tidepools  8/V/74;1235  27/V/74;1535 18.2° C;22.3%« Tidepools  Head length (mm) 0.30-0.49 0.50-0.69 0.70-0.89 0.90-1.09 1.10-1.29 1.30-1.49 1.50-1.69 1.70+ Total  T  M  3 41 33 15 6 24 10 20 15 2 2 138*  NF  3 8 1 -  RF  6 4 -  Subtidal trap, no bait l e f t T  M  NF  RF  T  M  NF  32 5 3 1  1  -  1  1  -  mostly adults  30 (approx.)  42  RF  Date;Time Temp.;Sal. Habitat Head length (mm)  4/Vl/74;1100 17.0° C;19.6%. Seaweeds (few i n pools) T  M  NF RF  4/Vl/74;1100 Subtidal trap T. M  NF  RF  0.30-0.49 0.50-0.69 0.70-0.89 0.90-1.09 1.10-1.29 1.30-1.49 1.50-1.69 1.70+  18 14 9 12 5 7 2  Total  67  87*  Date;Time Temp.;Sal. Habitat  18/Vl/74;0950 19.5° C;20.5%„ Subtidal trap, no bait l e f t  24/Vl/74;1420  Head length (mm) 0.30-0.49 0.50-0.69 0.70-0.89 0.90-1.09 1.10-1.29 1.30-1.49 1.50-1.69 1.70+  T  5 3  M  5 11 1 6 - 1 1 - 1  NF RF  none mea 4 2 1 3 2 1 1  1 1  4 7 10 1 28 10 26 12 10 6 2 2  -  6 24 49 27 16 5 5  NF RF  5 -  -  NF RF  9/VII/74;1400 19.3° C;22.1%„ Seaweeds (few i n pools) T  M  NF RF  16 44 27 18 10 2 6 4 3 - 1 1 1 -  110*  Date;Time Temp.;Sal. Habitat  22/VIII/74;1315 19.6° C;22.6% Seaweeds (few i n pools)  Total  M  -  11  0.30-0.49 0.50-0.69 0.70-0.89 0.90-1.09 1.10-1.29 1.30-1.49 1.50-1.69 1.70+  M  none measured but many found including many ovigerous females  1 1  T  111  Seaweeds (few i n pools) T  Total  Head length (mm)  5 4 - 18 - 14 4 -  18/Vl/74;0950 .19.1° C;24.2%« ..Seaweeds (few i n pools)  30/VIl/74;0950  13/VIII/74;0715  Seaweeds (few i n pools)  Seaweeds, tidepools  0  T  M  NF RF  none measured, but many found including many ovigerous, females  T  M  7 19 31 33 20 9 9 1 1  100*  NF RF  8 S  T  5 -  Few  M  NF RF  104  Date;Time Temp.;Sal. Habitat Head length 0.30-0.49 0.50-0.69 0.70-0.89 0.90-1.09 1.10-*i:29 1.30^-1.49 1.50-1.69 1.70+ Total.  29/VIIl/74;0915 22.0° C;21.3% Seaweeds (none i n pools) 0  (mm)  T  M  NF  RF  2 1 2  -  -  2  5  13/IX/74;0845 23.0° C Seaweeds, tidepools T  0  M  NF  RF  APPENDIX B. Means and sample standard deviations f o r length vs. age data of males and females at d i f f e r e n t temperatures and s a l i n i t i e s (food:  Enteromorpha i n t e s t i n a l i s ) .  106  Appendix B.  Head length vs. age i n weeks.  , males;  females (lines connect weekly means); represent  ,  vertical lines  one sample standard deviation on either side  of the means.  107 10 C, 12-14%. 1-B  Males, N=9;  Females,  N=ll  1«6.  %  1«£.  TH  1-4.  I'D..  LO LJ —11  h) X  0-8 . o.&. 0-4. o-a. 0-0  b  !£>•  11-  12-  13.  14.  IS.  lO-  ll-  12"  13-  14-  IS-  10.  ii-  12-  13«  14.  IS-  10 C, 18-21%.  i-a. Males, N=14;  Females,  N=9  1-6.  1 I  1-4.  1-  i-a.  S_J  o-a.  • <•  UJ  I  O'B. 0.4. o.a. 0-0 4. 10 C, 24-28%. l-a.  Males, N=10;  Females,  N=ll  i«e.  ^  S  1-4. l'E.  1-0.. O.B.  _J n  £J3  °' £  0-4. o-a. -+—t-  -+-  a.  WEEKS  108  d  20  i-a  C,  Males,  12-14%. N=9;  Females,  N=12  i-a. 1-4.  i-o.  ID  o-a.  J •  o-a. 0-4.  X  ca. O-Q 920  1 , a  r  C,  Males,  H  1-  ID-  i l - 12.  13.  14.  IS-  10-  11.  12.  13-  14-  15-  10.  11.  12-  13-  14.  18-21%. N=7;  Females,  N=ll  i-a. i«4.  TH  1-S. ID  |  l-Q. o-a. o-a.  < id x  0-4. o«a. CO  f I.H  20  C,  Males,  24-28%.. N=10;  Females,  N=10  i-a  t Hi P  1-4 i-S i - a .  o-a.  n  o-a.  LJ X  0-4. 0.£. o-n  -f-  7.  -f-  a-  WEEKS  -4-  9.  APPENDIX C. Oxygen uptake of individual animals at d i f f e r e n t acclimation and test temperatures.  110  Appendix C.  Top graphs:  oxygen uptake/animal vs. dry body weight.  Bottom graphs: body weight,  oxygen uptake/dry body weight vs. dry x, animals acclimated to 10° C;  A,  acclimated to.20°'C;  , regression l i n e for  acclimation. = 10° C;  regression l i n e for  acclimation = 20° C (base 10 logarithms).  Ill  0 C  TEST TEMPERATURE LOG  Y =  0-2014  +•  0-6144  * LOG X  N =  17  —*  40.  0.1  1.  •RY WEIGHT TEST TEMPERATURE "T L O G  Y =  0-2014  10-  30-  (MG)  0 C + -0-3952  * LOG X  •RY WEIGHT CMG)  N =  17-*-  112  •RY WEIGHT (MG)  113  T E S T TEMPERATURE LEG Y = LOG Y =  40-  0-45B1 0-4831  10 +• +  C  0-70270-701B  * LEG X * LEGX  WEIGHT  (MG1  N = N =  17 — X — 17 — A —  1 5  in UJ  t—i  2 0-1 •RY  20 -  T E S T TEMPERATURE LEG LOG  Y =. Y =  0-4S2 0-47S5  10 C + +  -0-S373 -0-3320  » LEGX * LEG X  N = N =  i  I II I  1 7 - » 17  10-1 I-  or a \ nj •  in  0-4 0-1  H—I  I I I II  DRY WEIGHT CMG)  10-  30-  114  TEST TEMPERATURE 20 C UDG Y = 0 - 5 3 3 9 +• 0 - 7 5 3 9 40. L O G Y = 0 . 5 6 6 3 + 0-74O3  * LOG X * LOG X  N = N =  17— 17—  115  116  TEST LEG  TEMPERATURE  Y =  0-7795  30 *•  C  0-G91S  « LEG X  N =  40.  17 .  10-1  a.  C 5  1  1  1  1  I  H  I M I  0-1  1  1  I  1  1-  DRY TEST '"LEG  TEMPERATURE  Y =  0-7795  1  1  10>  WEIGHT 30  I I I I  30-  (MG)  C  + -0-3091  * LEG X  N =  17 — A -  10-  0-4 0-1  1  1  1—I  M i l l  1  1  1  1'  DRY  WEIGHT  (MG)  1  I  I I I I  10-  1  1  30-  

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