Temperature dependent mortality and behavioral changes in a freshwater mussel Lamellidens marginalis to dimethoate exposure.

ABSTRACT

Temperature is a crucial determinant of biogeography, directly affecting the behavioral responses of the organisms. An acute static bioassay was conducted to evaluate the effect of temperature on dimethoate toxicity in a freshwater mussel Lamellidens marginalis. The mussel, were exposed for 96 hr at different concentrations of dimethoate (155.00, 160.00, 165.00, 170.00, 175.00, 180.00, 185.00, 190.00, 195.00, and 200.00 mgl-1) in the month of January when water temperature was 14.9±1.20C and at concentration 35.00, 37.00, 39.00, 41.00, 43.00, 45.00, 47.00, and 49.00 mgl-1 in the month of August when the water temperature was 28.0±0.50C. The LC50 values were calculated from the mortality data obtained (using EPA-Probit analysis version 1.5, statistical software). The 96 hr LC50 value recorded at higher temperature was 36.34mgl-1 and at low temperature was 163.59 mgl-1. The mussel exposed at higher temperature showed more sensitive behavioral responses like huge mucus secretion, sudden closure of shell valves, quick post-mortem changes and increased oxygen consumption in comparison to exposure at low temperature. Therefore, the increasing threat of global warming increases the risk of pesticide toxicity in the exposed organisms.