FISHERY BULLETIN: VOL. 75, NO. 1 



increase was very highly significant (P<0.001). 

 This observation points to elevated pentose shunt 

 activity in the livers of exposed fish. We construe 

 this to be a compensatory mechanism, providing 

 metabolites for increased rates of biosyntheses, to 

 enable impaired biochemical systems to maintain 

 near-normal function. Similar inductive response 

 after sublethal metal challenge has been observed 

 in other teleosts, such as the winter flounder: 

 elevated levels of two metalloenzymes in the kid- 

 ney and hematopoietic tissue after 60 days' ex- 

 posure to 0.01 ppm Cd (Gould in press), and ele- 

 vated levels of ornithine decarboxylase, another 

 pyridoxal phosphate enzyme, in the liver and 

 kidney after intravenous injection of methyl- 

 mercury, following an initial drop in activity 

 (Manen et al. 3 ). 



Chemical Uptake 



Gill, muscle, and liver tissues from each expo- 

 sure group were analyzed for cadmium uptake. In 

 contrast to the marked cadmium uptake in tissues 

 of cunners exposed for 96 h to cadmium at levels up 

 to 48 ppm (Greig et al. 1974), nearly all the sam- 

 ples from these 30- and 60-day exposures to both 

 0.05 and 0.1 ppm Cd, as well as controls, were 

 below the limits of detection (ca. 2 ppm, wet wt) for 

 the sample size and procedure used. 



CONCLUSIONS 



In summary, long-term exposures of the cunner 

 to 0.1 ppm Cd caused increased mortality, de- 

 pressed gill-tissue oxygen consumption, and 

 lowered transaminase and elevated pentose shunt 

 activity in the liver. 



The toxicity of cadmium to marine animals is 

 influenced, however, by such environmental 

 variables as temperature, salinity, pH, dissolved 

 oxygen (Gardner and Yevich 1969; Vernberg and 

 Vernberg 1972), and chemical form (Gould et al. 

 1976). Moreover, toxicity of cadmium varies with 

 different species: Westernhagen et al. (1974) and 

 Westernhagen et al. (1975) found that low salini- 

 ties enhance the toxicity of cadmium to the de- 

 veloping eggs of herring, Clupea harengus, and 

 needlefish, Belone belone, but Westernhagen and 



3 Manen, C. A., B. Schmidt-Nielsen, and D. H. Russell. 1976. 

 Alterations of polyamine synthesis in liver and kidney of winter 

 flounder in response to methylmercury. Unpubl. manuscr. Univ. 

 Ariz. Med. Cent., Dep. Pharmacol., Tucson, and The Mt. Desert 

 Island Mar. Biol. Lab., Salsbury Cove, Maine. 



Dethlefsen (1975) reported no such enhancement 

 using flounder, Pleuronectes flesus, eggs, possibly 

 because of the differences in the capacity of the egg 

 membranes to bind cadmium ions. The nature and 

 degree of cadmium's toxicity may well change 

 under different laboratory or field conditions. 



ACKNOWLEDGMENT 



We thank Rita S. Riccio for her critical reading 

 and typing of this manuscript. 



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