author(s)
Manju Rani, RK Gupta, Jyoti Yadav and Sandeep Kumar

abstract
The present study of 60 days was conducted to study the comparative inhibition of acetylcholinesterase activity due to the exposure of organophosphates viz. Malathion, dimethoate and chlorpyrifos when used unaccompanied as well as in combination on Indian major carps namely Labeo rohita and Cirrhinus mrigala. For this twelve concentrations were used. Dose dependent significant reduction in acetylcholinesterase activity of fishes exposed to pesticides has been observed. Reduction upto 24.1%, 12.6%, 14.3% and 18.4% in AChE activity has been observed in C. mrigala exposed to D+C+M (0.001 ppm), dimethoate (0.001 ppm), chlorpyrifos (0.001ppm) and Malathion (0.001ppm) respectively. While in L. rohita, decrease upto 24.7%, 13.7%, 15.1% and 19.2 has been detected in C. mrigala exposed to D+C+M (0.001 ppm), dimethoate (0.001ppm), chlorpyrifos (0.001 ppm) and Malathion (0.001ppm) respectively. However, Malathion induced maximum AChE inhibition and the effects were enhanced when Malathion was used in combination with chlorpyrifos and dimethoate that marks the synergistic mode of action of organophosphates. It may also be noted that pesticide induced enzyme inhibition was more in case of L. rohita as compared to C. mrigala.