Abstract
An investigation on the effect of the Azadirachta indica on the ovary of fresh water catfish Heteropneustes fossilis was carried out in the laboratory. Fishes were exposed to sub-lethal concentrations of Azadirachta indica for 24,48,72 and 96 hrs. The LC50 values of Azadirachta indica calculated for Heteropneustes fossilis for 24, 48, 72 and 96 hours are 10.5, 8.5, 7.0 and 6.5 ml/L respectively. The ovaries were removed for histological examination. The normal ovary of Heteropneustes fossilis showed developing follicles with large nucleus and several nucleoli, few degenerating oocytes were also seen but exposure leads to shrinkage of oocytes, vacuolated cytoplasm, degenerating vitellogenic follicles, disintegrated interstitial tissues, necrosis and damaged follicles.