ACUTE AND CHRONIC EFFECTS OF COPPER, CHROMIUM AND INSECTICIDE-ENDOSULFAN ON LITTORAL CLADOCERA, PSEUDOSIDA VARIABILIS

Recent works have emphasized on the serious problems caused by the toxicity of pesticides and heavy metals on aquatic ecosystems due to human activities. The aim of this work was to evaluate the toxicities of an insecticide with endosulfan as active element and the metals copper and chromium on the littoral cladocera ctenopoda, Pseudosida variabilis. The lethal and sublethal effects on eight biological endpoints were analyzed paying special attention to the intrinsic rate of increase (r). The EC sub(50) values to copper, chromium and endosulfan were: 29; 133.2 and 1.75 mu l 1 super(-1) at 24 h and 12; 52.5 and 1.04 mu g 1 super(-1) at 48 h respectively. A comparison with other freshwater clado-cerans revealed that P. variabilis would be an appropriate species to be used as a test organism in ecotoxicological studies. A detailed analysis of each life history trait showed that copper, chromium and endosulfan had negative effects on several life history parameters. However, the r value was not the most appropriate endpoint of copper and chromium toxicity, when it was compared with other individual and population parameters. Survival, longevity, age of first reproduction and mean brood size were the most appropriate parameters for both metals. On the contrary, in case of endosulfan, this endpoint was severely affected, and the population consequences are discussed. The results suggest that multiple biological endpoints and an extended period of exposure are needed in order to achieve a better screening of metal and insecticide toxicity.