The effects of pesticide monocrotophos (organophosphate), on the ovaries of freshwater murrel, Channa punctatus were studied. Exposures for 15 and 45 days with histological preparations at 1 ml L-1, and 2 ml L-1 sublethal concentrations along with control were examined. Pre spawned 10 fish (47.85±0.75gm; 17.80 ± 0.50cm) were randomly stocked in 50 L aquarium in triplicate groups for each treatment levels. The effects of monocrotophs were analysed after 15 and 45 days of exposure, respectively. The control contained an abundance of the different stages of oocytes (Oocytes I, II, III, and IV) and had an intact ovigerous lamellae and follicular lining. The control also contained a thick and complete ovarian wall with evident previtelline and euvitelline nucleoli. After 15 days of exposure the gonado somatic index (GSI) significantly (P<0.05) decreased in the two exposure concentration, where the maximum decrease in both GSI and ovary was observed at higher concentration i.e. 2 ml L-1 compared with control. Decreased vitellogenesis and oocyte atresia was also observed at higher concentration. While after 45 days of exposure a significant (P<0.05) increase in oocyte atresia and decreased vitellogenises was recorded with clear indication of vacuolization and tissue necrosis. On the basis of the above finding it is concluded that widely used organophosphate monocrotophos in agriculture has produced significant toxic effects on gonodal development of Channa punctatus.
