Effects of Pesticides Chlorpyrifos and Dimethoate on Moulting in Macrobrachium Rosenbergii (de Man)

The indiscriminate use of pesticides has led to the contamination of air, soil, surfacewater, groundwater and vegetation. Moreover, pesticides have impacted many non-target vegetation and organisms. Studies show that many pesticides enter the ecosystem and act in a manner that may enhance the effects of other pesticides, while still others may accumulate in the organisms causing long term changes in them. In the present study, an attempt has been made to show the individual and synergistic effects of two organophosphorous pesticides viz. Chlorpyrifos and Dimethoate on the giant freshwater prawn Macrobrachium rosenbergii (de Man), in terms of the process of moulting observed over a period of 28 days under laboratory conditions. The process of moulting can be taken as a parameter to observe the sub lethal effects of the pesticides. The prawns showed stress and the process of moulting was affected with the treatment of pesticides. Individual effect of pesticide, Chlorpyrifos caused greater stress than Dimethoate as compared with the control group. Similarly it was observed that synergistically Dimethoate enhances (positive synergism) effect of Chlorpyrifos leading to greater toxic effects even at lower concentrations in terms of delay, deformities and mortality during moulting. Hence, the present study shows the potency of pesticide toxicity individually and synergistically on moulting in prawns.