Influence of acclimation and exposure temperature on the acute toxicity of cadmium to the freshwater snailPotamopyrgus antipodarum(hydrobiidae)

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Abstract Forty-eight-hour acute toxicity tests were performed to determine the influence of acclimation temperature (5, 15, and 20°C) and exposure temperature (5, 15, and 20°C) on the toxicity of cadmium to the freshwater gastropod Potamopyrgus antipodarum. Mortality varied with cadmium concentration and treatment conditions, but did not conform to conventional sigmoid concentration-response (i.e., dose-response) relationships. Because the shapes of the concentration-response curves were treatment dependent, a nontraditional approach for data analysis was employed. Regardless of acclimation temperature, mortality increased with increasing exposure temperature, and at all exposure temperatures snails acclimated at 15°C were most susceptible to cadmium toxicity. Estimated LC50 values were within 1 to 4 mg Cd/L. Although the shapes of the concentration-response curves were different for each treatment, the slopes were generally quite steep, indicating a uniform response for the whole population. At a given Cd concentration, acclimation temperature and exposure temperature accounted for 57 and 40%, respectively, of the variation in mortality, and LC50s changed by a factor of four. The results indicate that changes in environmental variables can alter both the degree of response and the response distribution of a population, and that past as well as prevailing environmental conditions can influence organismic responses to toxicants.

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