A Study on the effect of organophosphorus insecticide phorate on brain histopathology of the common carp Cyprinus carpio

Abstract

The present study is aimed to investigate the effect of sublethal concentrations of phorate on the histopathology of brain in the common carp, Cyprinus carpio (C. carpio). Fish were exposed to chronic sublethal toxicity (one-tenth of the LC50/96 hours - 0.071 ppm/l) of phorate (CSTP) for one day, 7, 15 and 30 days and the chronic toxicity tests were carried out under laboratory conditions. On exposure for a period of one day to CSTP, necrosis of neurons, formation of minor vacuoles with degeneration of neural cells and distended sinusoids were observed in the brain of the fish. Significant hemorrhage was also noticed at some places. On exposure for a period of 7 days to CSTP, further structural damage, intracellular oedema and pycnotic nuclei were observed in the brain of the fish. After 15 days of exposure period there was an increase in necrosis of neurons, cytoplasmic vacuolization and lesions in the brain of the fish. After the exposure period of 30 days, reorganized neuronal tissue with indistinct nuclei was observed in the brain of the fish. The findings of the present study suggest that the frequency of pathological changes increase with the increasing exposure time to CSTP.