Organ specific histopathology and brain acetylcholinesterase inhibition in rohu, Labeo rohita and silver barb, Barbonymus gonionotus: Effects of three widely used organophosphate pesticides

Agricultural pesticides, eventually find their ways to aquatic ecosystems by different routes adversely affect the aquatic biota. To determine its potential hazards, acute toxicity tests (LC₅₀) of three commonly used organophosphate pesticides, Envoy 50SC, Samcup 50EC and Dursban 20EC on Labeo rohita and Barbonymus gonionotus were performed. The LC₅₀ (P<0.05) of these pesticides were estimated at 0.110 (0.060-0.199), 0.217 (0.204-0.231) and 0.079 (0.073-0.084) ppm for L. rohita and 0.471 (0.440-0.500), 0.789 (0.754-0.824) and 0.273 (0.260-0.286) ppm for B. gonionotus, respectively. Pesticides abruptly altered the normal structures in various fish organs like gills, kidney and liver. The major alterations included missing gill lamellae, gill clubbing, fungal granuloma, fatty degeneration, lipid droplet formation, degenerating glomeruli and kidney tubules, hyperplasia, hemorrhage, pyknosis, increased number of vacuoles, and necrosis. Envoy 50SC, Samcup 20EC and Dursban 20EC showed significant inhibition on L. rohita AChE activity at 216.7±11.0, 207.3±5.0 and 146.7±5.5 nmol/min/mg protein, respectively. In B. gonionotus, Samcup 20EC and Dursban 20EC showed significant inhibition (P<0.05), which were recorded as 242.0±6.6 and 221.7±60.3 nmol/min/mg protein, respectively. Furthermore, pesticide treated L. rohita showed higher enzymatic inhibition (51.49%) than B. gonionotus (19.60%).