Toxic effect of phorate on the histopathology of muscle in the fresh water fish Cyprinus carpio exposed to lethal concentrations

Fingerlings of Cyprinus carpio (C. carpio) fish were exposed to acute lethal toxicity (LC50/96 hours - 0.71 ppm/l) of phorate (ALTP) for one day and 4 days and the toxic effect of acute lethal concentrations of phorate on the histopathology of muscle was investigated in the present study. Lethal concentration (LC50) of phorate to C. carpio was determined by the probit method of Finney and the LC50 of phorate was taken as lethal concentration for acute toxicity study. On exposure for a period of 1 day to ALTP, splitting of muscle fibers followed by their thinning was observed in the muscle of the exposed fish. The muscle fibers exhibited longitudinal splitting with pyknotic nuclei. On exposure for a period of 4 days, a further increase in the longitudinal splitting of muscle fibers with pyknotic nuclei and cellular degeneration were observed. Karyolysis seems to have occurred as granular debris. The isolation of muscle fibers from one and another was noticed with necrotic changes. The findings of this study demonstrated that the histopathological changes induced by ALTP in the muscle of C. carpio were not only dependent on the concentration of the pesticide but also on the length of the fish exposure period.