Physiological Response of the Cunner, Tautogolabrus adspersus, 
to Cadmium. 
III. Changes in Osmoregulation and Oxygen Consumption 
FREDERICK P. THURBERG and MARGARET A. DAWSON!’ 
ABSTRACT 
The cunner, Tautogolabrus adspersus, was exposed to various concentrations of cadmium, 
as cadmium chloride (CdCl, -2'’2 H,O), for 96 hr. At the end of this exposure period tests of blood 
serum osmolality and gill tissue oxygen consumption were performed. High levels (48 ppm) of 
this metal resulted in an abnormally high serum osmolality and an exposure as low as 3 ppm 
reduced the normal rate of oxygen consumption. Both of these parameters may be related to 
observed tissue damage. 
INTRODUCTION 
Cadmium, which is neither essential nor beneficial 
to aquatic organisms (McKee and Wolf, 1971), has 
been detected in increasing amounts in the tissues of a 
number of such animals (Mullin and Riley, 1956; 
Peden et al., 1973). The use of cadmium in a variety of 
industrial processes has increased in recent years, 
making this metal an immediate concern as an en- 
vironmental pollutant (U.S. Council on Environmen- 
tal Quality, 1971; Dean, Bosqui, and Lanouette, 
1972). A number of investigators have demonstrated 
the toxicity of this metal to aquatic animals (Eisler, 
1971; Calabrese et al., 1973; Collier et al., in press); 
however, little is known of the sublethal effects of cad- 
mium on finfish. Other metals have been shown to 
alter serum osmolality and respiration of freshwater 
fish (McKim, Christensen, and Hunt, 1970; Lewis 
and Lewis, 1971). Few experiments in this area have 
been conducted with metals and marine fish and 
fewer still with cadmium as the test pollutant. The 
present study was undertaken to determine the effect 
of cadmium on osmotic regulation and oxygen con- 
sumption in the cunner, Tautogolabrus adspersus. 
METHODS AND MATERIALS 
Cunners were exposed to 0, 3, 6, 12, 24, and 48 ppm 
cadmium for 96 hr by the method of Calabrese, 
Collier, and Miller (this report, Part I). At the end of 
this exposure period, a blood sample was drawn by 
heart puncture using a scalpel and a disposable 
Pasteur pipette. Pooled blood samples from three to 
4 Milford Laboratory, Middle Atlantic Coastal Fisheries Center, 
" National Marine Fisheries Service, NOAA, Milford, CT 06460. 
four fish per cadmium concentration were collected in 
chilled 15-ml centrifuge tubes and spun at 1,720 X g 
for 20 min at 4°C. The osmolality in milliosmoles per 
Kg H,O (mOsm) of 0.2-ml serum samples was read on 
an Advanced 3L Osmometer.’ Gill tissues from these 
same fish were dissected out and placed in 15-ml 
Warburg-type flasks chilled on ice; each flask con- 
tained 5 ml of cadmium-treated seawater from the 
tank from which the fish were removed. Oxygen con- 
sumption was monitored over a 4-hr period in a Gilson 
Differential Respirometer at 20°C. Oxygen consump- 
tion. rates were calculated as microliters of oxygen 
consumed per hour per milligram dry weight of gill 
tissue (yl/hr/mg) corrected to microliters of dry gas at 
standard temperature and pressure. 
RESULTS 
Cunners exposed to 3-24 ppm cadmium for 96 hr 
showed no change in serum osmolality from the nor- 
mal value of approximately 340 mOsm determined in 
control fish. This value is lower than that of the sur- 
rounding seawater (630 mOsm). Osmoregulatory dif- 
ficulties were noted in fish exposed to 48 ppm. Serum 
osmolality in these fish rose to an average value of 390 
mOsm. These data are presented in Figure 1; each 
point on the curve represents the mean of six pooled 
samples, one from each of six exposures at a given 
cadmium concentration. 
Cadmium reduced the gill tissue oxygen consump- 
tion rates at all concentrations tested. A normal rate 
of 0.750 « l/hr/mg was reduced to approximately 0.510 
ul/hr/mg after exposure to cadmium at concentrations 
? Reference to trade names does not imply endorsement by the 
National Marine Fisheries Service, NOAA. 
