Acute toxicity of endosulfan 35EC to two freshwater bivalve molluscs from Godavari river at Maharashtra State, India.

Static bioassay tests were conducted using commercial grade endosulfan 35EC to study its toxicity during different seasons to two species of Lamellidens from the Godavari river at Paithan (Maharashtra State). Acute toxicity studies for 96 h showed that both species of Lamellidens were more sensitive to endosulfan 35EC in summer, at times of high temperature, pH and total carbonate content of the water used, than in monsoon and winter. LC0 and LC50 values were determined for L. corrianus and L. marginalis, during summer, monsoon and winter. Statistical analyses showed that both species were more sensitive during summer (P less than 0.001) than in monsoon and winter and that L. marginalis was more sensitive to endosulfan 35EC than L. corrianus in summer (P less than 0.001). Behavioural changes and mortality of the bivalves were dose-related. Regression equations and 95% confidence limits for each species were established in different studies. The results are discussed in the light of possible effects of endosulfan on these species of bivalve molluscs.