THE INFLUENCE OF TEMPERATURE AND SALINITY ON THE 

 TOXICITY OF CADMIUM TO THE FIDDLER CRAB, UCA PUGILATOR 



James O'Hara^ 



ABSTRACT 



The concentrations of cadmium lethal to the fiddler crab, Uca pugilator, were determined 

 for various environmental regimes of temperature and salinity. Mortality was greatest 

 in high temperatures and low salinities when tested for 240 hr. Concentrations of cad- 

 mium were greatest in green gland followed by gill, hepatopancreas, and muscle. 



The waste discharge of electroplating plants, 

 lead and zinc mines, and chemical plants fre- 

 quently contains toxic cadmium salts which 

 contribute to the widespread environmental pol- 

 lution (McKee and Wolf, 1963), and the impor- 

 tance of this pollutant has been stressed by its 

 relationship with the crippling "itai-itai" disease 

 of Japan (Kobayashi, 1971). The effects of 

 cadmium on aquatic organisms have been in- 

 vestigated for numerous freshwater organisms 

 (Doudoroff and Katz, 1953; Ball, 1967; Mount 

 and Stephan, 1967), and while the cadmium is 

 normally flushed down to the estuarine and ma- 

 rine environments, only Gardner and Yevich 

 (1970), Jackim, Hamlin, and Sonis (1970), and 

 recently Eisler (1971) have examined the ef- 

 fects of cadmium on estuarine forms. Eisler 

 alone has reported the effects of normal varia- 

 tions in salinity and temperature on the toxic 

 effect of cadmium on mummichogs. 



The present report is part of a program to 

 examine the effects of chronic exposure of cad- 

 mium to fiddler crab, Uca pugilator. This study 

 examines the synergistic role of salinity and 

 thermal stress on the acute toxicity of cadmium 

 to the crabs. 



^ Belle W. Baruch Coastal Research Institute, Uni- 

 versity of South Carolina, Columbia, SC 29208. 



Manuscript accepted April 1972. 



FISHERY BULLETIN: VOL. 71, NO. 1, 1973. 



METHODS 



Fifteen adult male {x = 2.2 g) and 10 adult 

 female (x = 1.5 g) fiddler crabs were placed 

 in 23 X 30 cm plastic boxes along with 250 ml 

 of dilute filtered seawater. The containers were 

 slightly tilted in the incubator so that the crabs 

 could freely select total or partial immersion. 

 No avoidance of the toxic solution was noted. 

 Desired salinities were obtained by the addition 

 of distilled water. The cadmium stock for all 

 experiments was reagent grade CdCl2 • 2-1/2 H2O 

 made up to a stock solution of 1 mg Cd"^"^ per 

 ml water. Aliquots of this stock were added 

 to each test chamber to bring the cadmium con- 

 centration to the desired levels of 1.0, 5.0, 10.0, 

 25.0, and 35.0 ppm Cd"^"^. All crabs were kept 

 in constant temperature boxes on a 12-hr light- 

 dark photoperiod for the 10-day duration of the 

 experiment. The water was changed every third 

 day to reduce the buildup of metabolic wastes 

 and to keep the concentration of cadmium near 

 the nominal level. Preliminary tests indicated 

 no loss of cadmium from the test medium with- 

 out organisms. Eisler (1971) showed less than 

 5 /f loss from similar concentrations of cadmium 

 in dilute seawater. Dead organisms were re- 

 moved every 24 hr during the tests. 



To determine the synergistic effects of envi- 

 ronmental stresses on the toxicity of cadmium, 

 crabs were exposed- to the different cadmium 



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