Histopathological alteration in gill of the freshwater fish Pseudetroplus maculatus (Bloch, 1795) under chlorpyrifos toxicity

Abstract

Sublethal toxicity effects of organophosphorous pesticide, chlorpyrifos (O, O-Diethyl-O-3,5,6-trichloro-2-pyridy phosphorothioate) was investigated in the freshwater teleost fish, Pseudetroplus maculatus. Fishes were exposed to one-tenth of LC 50 concentration, ie., 0.661 µg/ L of chlorpyrifos for 24, 48, 72 and 96 h maintaining ten fishes in each group, along with the control group. At the end of every treatment period, animal was killed and the gill tissue was collected for the histopathological analysis. Control tissue showed normal gill architecture with compact lamellar gill epithelium, gill arches, primary and secondary lamellae. Gill of chlorpyrifos exposed groups were compared with that of control tissue and it was observed that no notable changes on the histology of gill at 24 h. Some structural alterations such as curling of secondary lamellae, fusion of adjacent secondary lamellae and hyperplasia of primary lamella were observed after 48 h of pesticide exposure. Interestingly, the complete destruction of secondary lamellae with vacoulization of primary lamellae was observed at the end of 72 h exposure. However, after 96 h of treatment period necrosis of the secondary lamellae and aneurism were noticed. Thus the pathological effect of chlorpyrifos was well documented from the present results and the intensity of gill tissue damage was observed in time-dependent manner. The present study illustrates that even at sublethal concentration of chlorpyrifos exposure at short-time duration could cause severe pathological lesions in fish and is of great threat to aquatic ecosystem.