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

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.