“Effects of Sublethal Dimethoate Exposure on Acetyl Cholinesterase (AChE) Activity in Clarias batrachus (Linn.)â€

The widespread use of organophosphorus insecticides in agriculture poses a serious threat to aquatic ecosystems, particularly to non-target organisms such as fish. Dimethoate is one of the commonly used pesticides that can enter freshwater bodies through agricultural runoff, leading to sublethal toxic effects. The present study investigates the impact of sublethal concentrations of Dimethoate on the specific activity of Acetyl Cholinesterase (AChE) in the freshwater edible fish Clarias batrachus (Linn.). Healthy specimens of Clarias batrachus were exposed to predetermined sublethal concentrations of dimethoate for a specific experimental period under controlled laboratory conditions. The activity of AChE enzyme was assayed in vital tissues such as brain, gill, and muscle using standard biochemical methods. The results revealed a significant inhibition of AChE activity in all tissues, with the highest inhibition observed in the brain, followed by gill and muscle tissues. The degree of enzyme inhibition was found to be both concentration- and exposure-dependent. The inhibition of AChE activity indicates disruption in normal neurotransmission due to accumulation of acetylcholine at synaptic junctions, leading to neurotoxicity. Behavioral alterations such as erratic swimming, loss of equilibrium, and reduced responsiveness were also observed in treated fish. These findings suggest that even sublethal levels of Dimethoate can induce significant biochemical and physiological stress in aquatic organisms. A significant elevation in Acetyl Choline content and inhibition in the activity of the Acetyl cholinesterase was observed in fishes with insecticide Dimethoate for 48 hrs. 72 hrs. and 96 hrs.