LONG-TERM CADMIUM STRESS IN THE CUNNER, 

 TAUTOGOLABRUS ADSPERSUS 



J. R. MacInnes, F. P. Thurberg, R. A. Greig, and E. Gould 1 



ABSTRACT 



The cunner, Tautogolabrus adspersus, was exposed for 30 and 60 days to 0.05 or 0.10 ppm Cd as 

 cadmium chloride. The mean gill-tissue respiratory rates exhibited by the control fish and those 

 exposed to 0.05 and 0.10 ppm Cd were 972, 736, and 665 /u.1 Oj/h-g dry weight, respectively, after 30 

 days and 1,036, 702, and 587 ijl\ Ch/h- g, respectively, after 60 days. Changes were also observed in the 

 activities of two liver enzymes, aspartate aminotransferase (depression) and glucose-6-phosphate 

 dehydrogenase (induction). Results are compared with those from other metal -exposure studies with 

 cunners and other teleosts. 



In recent years cadmium has become the subject of 

 numerous investigations to determine its toxicity 

 to various marine animals. These studies have 

 progressed from short-term exposures to deter- 

 mine the concentrations that cause death (Eisler 

 1971; National Oceanic and Atmospheric Ad- 

 ministration 1974; Westernhagen and Dethlefsen 

 1975), to long-term exposure studies to measure 

 physiological change caused by very low levels 

 (parts per billion, ppb) of cadmium (Eisler 1974; 

 Calabrese et al. 1975; Dawson et al. in press; 

 Gould in press; Thurberg et al. in press). Such 

 long-term physiological stress can lower an 

 animal's capacity to adapt to and survive in its 

 natural environment. 



In a recent collaborative study, a common coast- 

 al fish, the cunner, Tautogolabrus adspersus, was 

 exposed to cadmium for 96 h and examined for 

 changes in respiration, osmoregulation, cadmium 

 uptake, histopathology, enzyme chemistry, and 

 immune response (National Oceanic and At- 

 mospheric Administration 1974). In the present 

 study, cunners were exposed to cadmium for up to 

 60 days so that the effects of both exposure regimes 

 might be compared. Parameters selected for study 

 were gill-tissue oxygen consumption, liver en- 

 zyme activity, and cadmium uptake by various 

 tissues. 



Respiratory activity, a good indicator of the 

 general condition of a fish, has been related to 

 stress caused by such environmental variables as 

 temperature (MacLeod and Pessah 1973), salinity 



'Middle Atlantic Coastal Fisheries Center Milford Labora- 

 tory, National Marine Fisheries Service, NOAA, Milford, CT 

 06460. 



Manuscript accepted September 1976. 

 FISHERY BULLETIN: VOL. 75, NO. 1, 1977. 



(Olson and Harrel 1973), and heavy-metal pol- 

 lutants (Calabrese et al. 1975). Gill-tissue res- 

 piration correlates well with whole-animal res- 

 piration, particularly the standard or inactive rate 

 of oxygen consumption ( Vernberg 1956; Thurberg 

 et al. 1975). Thurberg and Dawson (1974) found 

 that a 96-h exposure to 3 ppm Cd caused a de- 

 pression in the cunner's rate of gill-tissue oxygen 

 consumption. The present study examines the 

 oxygen-consumption rates in excised gill tissue of 

 cunners exposed to lower cadmium concentrations 

 for much longer periods of time. 



Because the fish were small, biochemical testing 

 was restricted to the relatively large liver tissue 

 mass. Two enzymes were selected for assay: a key 

 enzyme of nitrogen metabolism that had been 

 tested in the earlier, short-term exposure of 

 cunners to high levels of cadmium (Gould and 

 Karolus 1974), and a magnesium-linked enzyme 

 whose activity in winter flounder, Pseudopleuro- 

 nectes americanus, tissues is affected by the fish's 

 exposure to sublethal levels of cadmium (Gould in 

 press). The first enzyme, aspartate amino- 

 transferase (E.C.3.6.1.L; AAT), is linked to the 

 production of animal energy (Gould et al. 1976), 

 and in cunners exposed to 24 ppm Cd for 96 h, 

 activity in the liver dropped to 40% of control 

 activity (Gould and Karolus 1974). The second 

 enzyme tested, glucose-6-phosphate dehydrogen- 

 ase (E.C.I. 1.1.49; G6PdH), is the first step in a 

 glycolytic pathway that produces metabolites for 

 reductive biosyntheses, and is found in abnor- 

 mally high amounts in tissues having the high 

 metabolic rates that often accompany stress 

 (Weber 1963). 



Besides the respiratory and enzyme studies, 



199 



