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Hematology of juvenile striped bass, Morone saxatilis (walbaum), acclimated to different environmental conditions
(',~rJ~p lIl~,~'htm. I'hy~*ol. D~7(~. I t,L 54A. Pt' 221 to 2 2 1 I ' v ~ l ¢ . * . m I'~,.~ I~lnltcd Irl (iri'ill lh'it~ls~t
H E M A T O L O G Y O F JUVENILE STRIPED BASS, M O R O N E S A X A T I L I S (WALBAUM), A C C L I M A T E D TO DIFFERENT ENVIRONMENTAL CONDITIONS L o u I s A. COURTOIS Department of Fish .and Game. Water Pollution Control Laboratory, Rancho Cordova,, CA 95670, U.S.A.
IRe('eirt,d 27 Auqnnt 1975) Abstract--- I. Juvenile striped bass wcrc acclimated to different combimttions o f temperature and salinity and l~:d a uniform test diet. 2. Changes in hcmatocrit, hemoglobin, totM scram protein, and serum electrolytes were correlated to different environmcutM factors.
INTROD
photoperiod and feeding programs were continued as previously described.
UC~i'ION
P r e v i o u s r e p o r t s o n p h y s i o l o g i c a l d a t a for m a n y fish species have e m p h a s i z e d p r i m a r i l y ~ t l m o n i d species. O t h e r g a m e a n d n o n g a m e species h a v e m a n y u n i q u e characteristics which pose endless questions concerning t h e i r p h y s i o l o g i c a l a n d b e h a v i o r a l r e s p o n s e t o the m a n y d i v e r s e a q u a t i c e n v i r o n m e n t s . T h e lack o f basic d a t a for t h e s e o t h e r species p r e s e n t s p r o b l e m s w h e n a t t e m p t i n g to assess their p h y s i o l o g i c a l state p r i o r t o utilization in e i t h e r e x p e r i m e n t a l research o r m o n i t o r ing p r o g r a m s . T h e s t r i p e d bass. Morone sa.x-atiti.~ ( W a l b a u m ) . is a g a m e species w h i c h o c c u r s in several different h a b i tats (fresh a n d saline) t h r o u g h o u t California. A n earlier r e p o r t ( C o u r t o i s , 1975) e x a m i n e d t h e b a s i c h e m a t o l o g i c a l c h a r a c t e r i s t i c s o f " w i l d " adtilt s t r i p e d b a s s c a p t u r e d in the S a c r a m e n t o River. Results i n d i c a t e d e x t r e m e variability o f b l o o d a n d s e r u m profiles for the s e v e r a l s p e c i m e n s s a m p l e d . F u r t h e r r e s e a r c h was n e e d e d t o d e t e r m i n e if variability r e s u l t e d f r o m env i r o n m e n t a l o r d i e t a r y causes. T h e p r e s e n t r e s e a r c h examines the hematological characteristics of laborat o r y a c c l i m a t e d M . sct.~ccttilis m a i n t a i n e d u n d e r c o n trolled temperature, salinities, and nutritional regimens. T h i s is t h e first r e p o r t o f physiologic~al acclim a t i o n o f this species t o m u l t i p l e e n v i r o n m e n t s .
MATERIALS
AND
METHODS
Fish used in this research were collected by hook and line from the Sacramento River near Knight's Landing, California. They were transported to the Ecology Institute, University of California, Davis. All fish were maintained in fresh water Ilow-through t~mks For 10 days at 18 4- I~C prior to experimental use to ensure a healthy fish stock. The 1972 modification of the Oregon test diet was fed ad lib. once each day. This formulation has been shown to contain sufficient nutrition to maintain a healthy stock fish (National Academy of Sciences, 1973). A feedingconditioning period of 4-5 days was required before the striped bass would readily accept this diet. Photoperiod controlled by an electric timer was set at 14L, 10D (hours). The entire fish stock was then transported to the National Marine Fisheries Service Laboratory at Tiburon, California where the acclimation and testing was completed. Both 221
Ac~'limation procedures The striped bass were subdivided into four difl~rent groups, each being acclimated Io different temperature/ salinity combinations, in all eases the dissolved oxygen levels were maintained above 6.0 mwl (ppm). The following is a description of the environmental conditions to which each group was acclimated. A. Warm fresh water dechlorinated city water, temperature 17.5 4- 0.5C. B. Cold fresh water--deehlorinated city water, temperalure I0.8 4- 0.3-C. C. Warm sea water--bay sea water 130 ppl), temperature 17.5 __. 0.5~C. D. Cold sea water--bay sea water (30 ppt). temperature 10.5 4- 0.5"C. The fish were maintained under the defined conditions for a minimum of 24 days prior to examination of blood parameters. Several different hematological indices were evaluated following the acclimation period.
Hematolocdical b~dices Each fish was removed from its acclimation tank, killed via electrical shock (Courtois, 1974), weighed to the nearest tenth of a gram, measured to the nearest millimeter and then a blood sample removed via cardiac puncture. The syringe had been previously heparinized (ammonium salt. 1000 U.S.P. units) and air dried. Several hematological parameters were determined for each test fish by sub-sampling the 0.4ml mixed-blood sample. Hematocrit (Hot) and hemoglobin (Hb) content (cyanomethmoglobin form] were evaluated using standard techniques (Blaxhall, 1972; Cannan, 195g). Serum protein, Na ÷ and K ÷ values were determined by sampling the clear serum layer above the packed cell mass in the mierohematocrit tubes. A hand refractometer gave direct readings of total serum "protein. and a flame photometer was used for electrolyte determinations. Results from these analyses are presented in Table 1. RESULTS
AND
DISCUS~SION
Examination of the data presents hematological p r o f i l e s for M . saxatilis a c c l i m a t e d t o different env i r o n m e n t s . P h y s i o l o g i c a l differences a r e e v i d e n t b e t w e e n g r o u p s . F u r t h e r c o m p a r i s o n s will b e m a d e d i s c u s s i n g t h e effect o f salinity a n d , secondly, t e m perature upon homeostatic condition.
222
l.~)uis A. (.'~ :~I.'RI()IS "|'able I. I lcmi~tological analysi~ of juvenile slripcd bass i~cclin~atcd Io different en-
vironmental conditions Cold F r ~ h
Nanm Fresh
Cold Smlt
Wlrm S~It
W~.~. wt. t ~ )
79.1",.10-°(~) 1
hli.gts.hlS) 1
l~7.~.6.1~i7~ 1
56.2+6.617) 1
I.~n~;t n (era)
18.9_+0.8
15.'~.O.7
l&. 1-0.6
17.1-0.6
Set (I)
5h.111.6
57.h*I.2
h6.0~l. 3
hS, )Ii.0
8b ( ~n/lC/;,m "i)
/5. 9010.77
8. 827.O. li~
8. hO?O. 19
8. 3570.19
kro~. {gmll¢'~ m2) Nn*
(m~q/l)
~¢* lr~,,q/l ~
I0.)?*0.55
7.75.O.5-3
).ahlO. 38
7. ~,h?O.7h
16311
106Ll
18h*l
I~0-_2
O. ~;..o.1
~. ~.L'O.~
O. h:.O.O
O. 8-_0.1
iValu.~ are ~he ne~1 ~ 1 ~.E. and the number o~ s~mpl~n i s in parenthesis.
Salinity Results indicate salt water-acclimated A.I. saxatilis to have significantly lower blood parameters, ~rt, m K* and hitzher .~rum Na ~ Icvcls than fresh water Itcclimaled lish held at similar temperatures. The levels of signiticance as well as interpretations will be discussed for each particular parameter. Salt water-acclimated M. saxatilis had significantly lower |-let and l-lb than Iheir fresh water counterparts at similar temperatures (signilicantiy diltizrent at the 97.5% level, Sludents t tcstk This corresponds to rest, Its reported by other workers. Stanley & Colby (1971} reported increased Hct for fresh wateracclimated alewife. /11o~1 pseu~hdlaren
Temperature Increased tcmperalure appears to cause reverse effects in fresh- and salt water-acclimated M. saxatilis. Fresh water-acclimated fish at higher temperatures displayed simaificantly lower plasma protein levels compared to fish acclimated to lower temperature (sigmificant at the 97.5% level, Students t test). The reverse situation occurred in salt water-acclimated fish. Cold-acclimated salt water fish displayed significantly lower plasma protein levels [significant at the
99.5",, level, Students t test) than tile group acclimated to warm ~llt water. Perhaps this is a compensatory mechanism which would permit cold fresh water-acclimated M. stlxtuili.s to adjust to higher saiinities by maintaining elevated plasma protein levels to decrease the osmotic gradient existing across the gill menfl~rane in a .,~dt water environment. The feeding level was approximately thc ~mac in both coldacclin'mlcd groups: the only nmjor difference was the ~dinity. A second parameter which also displays a reversal in fresh vs ~llt water is serum Na*. The cold fresh water-acclimated tish had signiticantly reduced serum Na + compared to the warm-acclinaated fish (significant at the 95", level, Students t test). The cold salt water-acclimated fish displayed an elevated serum Na + compared to the warm salt water fish (significantly different at the 90% level, Students t testL The cold-acclimated lish in both e n v i r o n m e n t s (fresh or salt water) could be experiencing osmoregulatory breakdown. Umminger (1971)suggested this as the cause for a decrease in serum electrolytes in fresh water fish. If breakdown did occur at lower temperatures, the osmotic gradient across the gill would favor Nit + dilution in fresh water and concentration in sea water. Zaugg et al. ([9721 reported a similar response of young steelhead I-Stlhno yairdneri) to a reduction in ambient temperature. They reported that steelhead held in cold {10"C) fresh water increased their branchial N a + - K + ATPase activity during parr-smott transformation, but fish held at higher temperatures (15 or 20~C) did not have increased activity. The effects of the elevated temperatures decreased the n u m b e r of the fish which would normally be able to migrate to sea. The colder temperatures were necessary to prepare the fish for seaward migration. Without an increase in N a * - K + ATPase activity, the tish would have difficulty surviving in a hyperosmotic e n v i r o n m e n t (Maetz. 1971) and thus display osmoregulatory instability. The decrease in serum electrolytes a n d increase in protein content, as reported in the present research, could function to prepare the juvenile striped bass for salt water habitation. The protein content could act in a transient manner, allowing M. saxatilis to survive in a salt water environment by transiently increasing serum osmolality, thus decreasing the osmotic gradient across the gill membrane. W h e n the density of the chloride cell (Maetz, t971) reached a level 1o permit normal osmoregulation, the serum protein
Hematology of juvenile striped bass level could decrease. The increased number of chloride cells would provide adequate N a + - K + ATPase activity to handle the higher osmoregulatory demands placed on the fish at higher salinities. Full N a + - K + ATPase acclimation in anadromous species has been reported to require approximately 20 days (Zaugg & McLain, 1970) which is within the acclimation period reported here. Environmental inltuences upon the physiological state of a fish need to be delined prior to establishing how man-induced intluences modify these parameters. This report has established baseline physiological data for M. saxatilis acclimated to several different environments. Comparison of this data to previous reports (Courtois, 1975) reveals more physiological consistency. Explanations for this lower parameter variability appears to be one of two alternatives. First, the earlier investigation ~amplcd "'wild" breeding adults. Reproduction would place these animals under extremes of metabolism and osmorcgulation. Additional investigations of reproductive influences upon these proliles should be examined. Secondly, dietary effects upon the physiological profiles should bc examined. The diet utilized in the present investigation may or may not parallel that available to the "'wild" fish. Several other diets should be evaluated to point out any physiological modifications. Aeknowle@ements-This work is part of a doctoral dissertation for the University of California, Davis. The research was supported by the National Institute of Health (Tyaining Grant Number E5 125-5) administered through the Deparmlent of Environmcmal Toxicology, University of California. Davis. CA, U.S.A. This research was completed at the National Marine Fisheries Service Laboratory, Tiburon. California through the generosity of Dr. Robert W. Brocksen who provided the laboratory space.
REFERENCES
BLAXHALL P, C, (1972) The hematological assessment of the health of fresh water fish. A review of selected literature. d. Fish Biol. 4, 593-604.
223
Cannon R. K, (19581 Proposal for a certified standard for use in l~cmaglobinonlctry, Sccoml and final report. Clin. Chem. 4(31, 246-251. CouIcrols L. A. {19741 Physiological responses of striped bass, Roceus so.vat(Its (Walbau,nL to changes in diet. salinity, temperature, and,acute copper exposure. Ph.D, Dissertation, University of California. Davis, 118 p. O~URTOlS L. A, (19751 Blood and serum analyses of adult striped bass, Morone saxatilis, captured in the Sacramenlo River. C.1(£ Fish and Game (In pressJ. DIiVLAMINGV. L, & SAc;l: M. 11973) Osmoregulation in the eurvhaline elasmobranch. Dasytis sob(m,. Comp. Bioehent, fihj'sioL 45A, 31-44. I"OS'I'I~RM. A. {1969). Ionic and osmotic regulation in three species of cottus (Cottidae, telecost). Cotttp, Biochcnt. Physiol. 30, 751-759. Hot;sroN A. H, (1964) On passive lbatures in the osmoregulatory adapt(on of anadromot,s salmonids to sea water, J. Fish Res. Bd Can. 21. 1535x1538. Lurz P. (19721 Ionic and body compartment responses to increasing salinity in the perch. Percafluriutilis. ('onlp. Biochem. Physiol. 42A, 711--717. MAI.:TZJ. (1971) Fish gills: mechanisms of salt transfer in fresh water and sea water. Phil. "17"ans. R. Soc. Set. B 262, 209-249. MOTtoS R., ROMF.UF. G. & MArTZ J. [1965) Mechanism ofeuryhalinity--comparativeinvestigation of Pkaichthys and Serramts following their transfer to fresh water. C.r. hebd. Seanc. Acad. Sci.. Paris 261,801-804. NATIONAl` ACADEMY OF SCIENCES 11973) Nutrient requirements of trout, salmon, and catfish. Number 11, National Academy of Sciences, Wash.. D.C. 57 p. RIZNI:ROJ. L. & HILl. L. G. (1973) Sodium balance of the red river pupfish. Cyprino&m ruhro[hwhttilis. Comp. Biochem. PhysioL 44A. 1353~-1367. Sr,,,Nl.t~v J. G. & Col`v~vP. J. (1971) Effects of temperature on electrolyte balance and osmoregulation in the alewife (Alosu l~seudoharemluS) in fresh arm sea water. Trans. Am. Fish. Soe. 100/4), 624-638. UMS.UNGERB. L. (1971) Patterns of osmoregulation in fresh water fish at temperatures near freezing. PhyshK ZooL 44( 1). 20-27. Z,~UGG W. S. & McLAIN L. R, (1970) Adenosinetriphosphatase activity in gills of salmonids: seasonal variations and salt water influence in coho salmon, Ottcorhyttchus ki.sTadt. Comp. Biochenl. PhysioL 35, 587-596. ZAt:GG W. S., ADAMSB. U & MeLtoN L. R. (1972) Steelhead migration: potential temperature effect its indicated by gill adenosine triphosphatase activities. Science. N.Y. 176, 415-416.
H E M A T O L O G Y O F JUVENILE STRIPED BASS, M O R O N E S A X A T I L I S (WALBAUM), A C C L I M A T E D TO DIFFERENT ENVIRONMENTAL CONDITIONS L o u I s A. COURTOIS Department of Fish .and Game. Water Pollution Control Laboratory, Rancho Cordova,, CA 95670, U.S.A.
IRe('eirt,d 27 Auqnnt 1975) Abstract--- I. Juvenile striped bass wcrc acclimated to different combimttions o f temperature and salinity and l~:d a uniform test diet. 2. Changes in hcmatocrit, hemoglobin, totM scram protein, and serum electrolytes were correlated to different environmcutM factors.
INTROD
photoperiod and feeding programs were continued as previously described.
UC~i'ION
P r e v i o u s r e p o r t s o n p h y s i o l o g i c a l d a t a for m a n y fish species have e m p h a s i z e d p r i m a r i l y ~ t l m o n i d species. O t h e r g a m e a n d n o n g a m e species h a v e m a n y u n i q u e characteristics which pose endless questions concerning t h e i r p h y s i o l o g i c a l a n d b e h a v i o r a l r e s p o n s e t o the m a n y d i v e r s e a q u a t i c e n v i r o n m e n t s . T h e lack o f basic d a t a for t h e s e o t h e r species p r e s e n t s p r o b l e m s w h e n a t t e m p t i n g to assess their p h y s i o l o g i c a l state p r i o r t o utilization in e i t h e r e x p e r i m e n t a l research o r m o n i t o r ing p r o g r a m s . T h e s t r i p e d bass. Morone sa.x-atiti.~ ( W a l b a u m ) . is a g a m e species w h i c h o c c u r s in several different h a b i tats (fresh a n d saline) t h r o u g h o u t California. A n earlier r e p o r t ( C o u r t o i s , 1975) e x a m i n e d t h e b a s i c h e m a t o l o g i c a l c h a r a c t e r i s t i c s o f " w i l d " adtilt s t r i p e d b a s s c a p t u r e d in the S a c r a m e n t o River. Results i n d i c a t e d e x t r e m e variability o f b l o o d a n d s e r u m profiles for the s e v e r a l s p e c i m e n s s a m p l e d . F u r t h e r r e s e a r c h was n e e d e d t o d e t e r m i n e if variability r e s u l t e d f r o m env i r o n m e n t a l o r d i e t a r y causes. T h e p r e s e n t r e s e a r c h examines the hematological characteristics of laborat o r y a c c l i m a t e d M . sct.~ccttilis m a i n t a i n e d u n d e r c o n trolled temperature, salinities, and nutritional regimens. T h i s is t h e first r e p o r t o f physiologic~al acclim a t i o n o f this species t o m u l t i p l e e n v i r o n m e n t s .
MATERIALS
AND
METHODS
Fish used in this research were collected by hook and line from the Sacramento River near Knight's Landing, California. They were transported to the Ecology Institute, University of California, Davis. All fish were maintained in fresh water Ilow-through t~mks For 10 days at 18 4- I~C prior to experimental use to ensure a healthy fish stock. The 1972 modification of the Oregon test diet was fed ad lib. once each day. This formulation has been shown to contain sufficient nutrition to maintain a healthy stock fish (National Academy of Sciences, 1973). A feedingconditioning period of 4-5 days was required before the striped bass would readily accept this diet. Photoperiod controlled by an electric timer was set at 14L, 10D (hours). The entire fish stock was then transported to the National Marine Fisheries Service Laboratory at Tiburon, California where the acclimation and testing was completed. Both 221
Ac~'limation procedures The striped bass were subdivided into four difl~rent groups, each being acclimated Io different temperature/ salinity combinations, in all eases the dissolved oxygen levels were maintained above 6.0 mwl (ppm). The following is a description of the environmental conditions to which each group was acclimated. A. Warm fresh water dechlorinated city water, temperature 17.5 4- 0.5C. B. Cold fresh water--deehlorinated city water, temperalure I0.8 4- 0.3-C. C. Warm sea water--bay sea water 130 ppl), temperature 17.5 __. 0.5~C. D. Cold sea water--bay sea water (30 ppt). temperature 10.5 4- 0.5"C. The fish were maintained under the defined conditions for a minimum of 24 days prior to examination of blood parameters. Several different hematological indices were evaluated following the acclimation period.
Hematolocdical b~dices Each fish was removed from its acclimation tank, killed via electrical shock (Courtois, 1974), weighed to the nearest tenth of a gram, measured to the nearest millimeter and then a blood sample removed via cardiac puncture. The syringe had been previously heparinized (ammonium salt. 1000 U.S.P. units) and air dried. Several hematological parameters were determined for each test fish by sub-sampling the 0.4ml mixed-blood sample. Hematocrit (Hot) and hemoglobin (Hb) content (cyanomethmoglobin form] were evaluated using standard techniques (Blaxhall, 1972; Cannan, 195g). Serum protein, Na ÷ and K ÷ values were determined by sampling the clear serum layer above the packed cell mass in the mierohematocrit tubes. A hand refractometer gave direct readings of total serum "protein. and a flame photometer was used for electrolyte determinations. Results from these analyses are presented in Table 1. RESULTS
AND
DISCUS~SION
Examination of the data presents hematological p r o f i l e s for M . saxatilis a c c l i m a t e d t o different env i r o n m e n t s . P h y s i o l o g i c a l differences a r e e v i d e n t b e t w e e n g r o u p s . F u r t h e r c o m p a r i s o n s will b e m a d e d i s c u s s i n g t h e effect o f salinity a n d , secondly, t e m perature upon homeostatic condition.
222
l.~)uis A. (.'~ :~I.'RI()IS "|'able I. I lcmi~tological analysi~ of juvenile slripcd bass i~cclin~atcd Io different en-
vironmental conditions Cold F r ~ h
Nanm Fresh
Cold Smlt
Wlrm S~It
W~.~. wt. t ~ )
79.1",.10-°(~) 1
hli.gts.hlS) 1
l~7.~.6.1~i7~ 1
56.2+6.617) 1
I.~n~;t n (era)
18.9_+0.8
15.'~.O.7
l&. 1-0.6
17.1-0.6
Set (I)
5h.111.6
57.h*I.2
h6.0~l. 3
hS, )Ii.0
8b ( ~n/lC/;,m "i)
/5. 9010.77
8. 827.O. li~
8. hO?O. 19
8. 3570.19
kro~. {gmll¢'~ m2) Nn*
(m~q/l)
~¢* lr~,,q/l ~
I0.)?*0.55
7.75.O.5-3
).ahlO. 38
7. ~,h?O.7h
16311
106Ll
18h*l
I~0-_2
O. ~;..o.1
~. ~.L'O.~
O. h:.O.O
O. 8-_0.1
iValu.~ are ~he ne~1 ~ 1 ~.E. and the number o~ s~mpl~n i s in parenthesis.
Salinity Results indicate salt water-acclimated A.I. saxatilis to have significantly lower blood parameters, ~rt, m K* and hitzher .~rum Na ~ Icvcls than fresh water Itcclimaled lish held at similar temperatures. The levels of signiticance as well as interpretations will be discussed for each particular parameter. Salt water-acclimated M. saxatilis had significantly lower |-let and l-lb than Iheir fresh water counterparts at similar temperatures (signilicantiy diltizrent at the 97.5% level, Sludents t tcstk This corresponds to rest, Its reported by other workers. Stanley & Colby (1971} reported increased Hct for fresh wateracclimated alewife. /11o~1 pseu~hdlaren
Temperature Increased tcmperalure appears to cause reverse effects in fresh- and salt water-acclimated M. saxatilis. Fresh water-acclimated fish at higher temperatures displayed simaificantly lower plasma protein levels compared to fish acclimated to lower temperature (sigmificant at the 97.5% level, Students t test). The reverse situation occurred in salt water-acclimated fish. Cold-acclimated salt water fish displayed significantly lower plasma protein levels [significant at the
99.5",, level, Students t test) than tile group acclimated to warm ~llt water. Perhaps this is a compensatory mechanism which would permit cold fresh water-acclimated M. stlxtuili.s to adjust to higher saiinities by maintaining elevated plasma protein levels to decrease the osmotic gradient existing across the gill menfl~rane in a .,~dt water environment. The feeding level was approximately thc ~mac in both coldacclin'mlcd groups: the only nmjor difference was the ~dinity. A second parameter which also displays a reversal in fresh vs ~llt water is serum Na*. The cold fresh water-acclimated tish had signiticantly reduced serum Na + compared to the warm-acclinaated fish (significant at the 95", level, Students t test). The cold salt water-acclimated fish displayed an elevated serum Na + compared to the warm salt water fish (significantly different at the 90% level, Students t testL The cold-acclimated lish in both e n v i r o n m e n t s (fresh or salt water) could be experiencing osmoregulatory breakdown. Umminger (1971)suggested this as the cause for a decrease in serum electrolytes in fresh water fish. If breakdown did occur at lower temperatures, the osmotic gradient across the gill would favor Nit + dilution in fresh water and concentration in sea water. Zaugg et al. ([9721 reported a similar response of young steelhead I-Stlhno yairdneri) to a reduction in ambient temperature. They reported that steelhead held in cold {10"C) fresh water increased their branchial N a + - K + ATPase activity during parr-smott transformation, but fish held at higher temperatures (15 or 20~C) did not have increased activity. The effects of the elevated temperatures decreased the n u m b e r of the fish which would normally be able to migrate to sea. The colder temperatures were necessary to prepare the fish for seaward migration. Without an increase in N a * - K + ATPase activity, the tish would have difficulty surviving in a hyperosmotic e n v i r o n m e n t (Maetz. 1971) and thus display osmoregulatory instability. The decrease in serum electrolytes a n d increase in protein content, as reported in the present research, could function to prepare the juvenile striped bass for salt water habitation. The protein content could act in a transient manner, allowing M. saxatilis to survive in a salt water environment by transiently increasing serum osmolality, thus decreasing the osmotic gradient across the gill membrane. W h e n the density of the chloride cell (Maetz, t971) reached a level 1o permit normal osmoregulation, the serum protein
Hematology of juvenile striped bass level could decrease. The increased number of chloride cells would provide adequate N a + - K + ATPase activity to handle the higher osmoregulatory demands placed on the fish at higher salinities. Full N a + - K + ATPase acclimation in anadromous species has been reported to require approximately 20 days (Zaugg & McLain, 1970) which is within the acclimation period reported here. Environmental inltuences upon the physiological state of a fish need to be delined prior to establishing how man-induced intluences modify these parameters. This report has established baseline physiological data for M. saxatilis acclimated to several different environments. Comparison of this data to previous reports (Courtois, 1975) reveals more physiological consistency. Explanations for this lower parameter variability appears to be one of two alternatives. First, the earlier investigation ~amplcd "'wild" breeding adults. Reproduction would place these animals under extremes of metabolism and osmorcgulation. Additional investigations of reproductive influences upon these proliles should be examined. Secondly, dietary effects upon the physiological profiles should bc examined. The diet utilized in the present investigation may or may not parallel that available to the "'wild" fish. Several other diets should be evaluated to point out any physiological modifications. Aeknowle@ements-This work is part of a doctoral dissertation for the University of California, Davis. The research was supported by the National Institute of Health (Tyaining Grant Number E5 125-5) administered through the Deparmlent of Environmcmal Toxicology, University of California. Davis. CA, U.S.A. This research was completed at the National Marine Fisheries Service Laboratory, Tiburon. California through the generosity of Dr. Robert W. Brocksen who provided the laboratory space.
REFERENCES
BLAXHALL P, C, (1972) The hematological assessment of the health of fresh water fish. A review of selected literature. d. Fish Biol. 4, 593-604.
223
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