Toxic effect of malathion on acetylcholinesterase activity of liver, brain and gills of freshwater catfish Heteropneustes fossilis

The toxic effects of malathion were evident in the inhibition of acetylcholinesterase activity of liver, brain and gills of freshwater catfish Heteropneustes fossilis. Maximum inhibition of 77. 12% and 72.83% were recorded in brain and gills respectively after 72 hour of exposure to 4.80 mg/l pesticide. However, in liver highest inhibition of 67. 81% in enzyme level was noticed at 6.50 mg/l pesticide concentration after 24 hours of exposure, beyond which fish could not survive. Pesticide repressed the enzyme activity so intensely that it showed no sign of return to normalcy. The fish also elicited dissociated behaviour with increasing concentrations of pesticide toxicity.