Effects of Dimethoate (EC 30%) on Gill Morphology, Oxygen Consumption and Serum Electrolyte Levels of Common Carp, Cyprinus Carpio (Linn)

Synthetic pesticides are an important group of aquatic pollutants affecting health of fishes. This study is an attempt to assess the sub lethal effects of dimethoate, an organophosphate insecticide on gill morphology, ventilation rate, oxygen consumption and electrolyte levels of common carp (C. carpio). Healthy juvenile fishes were exposed to a sub lethal concentration of 0.96 mg/l (60% of 96 h LC50) of dimethoate; and at 24, 48 and 96 h exposure blood and gill tissues were collected, oxygen consumption and ventilation rate was determined. The changes in the gills of exposed fish were characterized by epithelial hyperplasia, lifting and degeneration of respiratory epithelium, lamellar bending and curling, fusion and disintegration of secondary gill lamellae. The degree of damage showed direct correlation with the duration of exposure. The electrolyte levels also fluctuated, levels of calcium decreased and phosphate levels increased during the exposure. Oxygen consumption and ventilation rate showed significant decrease at all exposure durations. The study demonstrates high sensitivity of fish gills to dimethoate, at short term and sub lethal exposure.