This study was designed to investigate the acute toxicities of endosulfan on the hematopoietic, gastro-intestinal, respiratory systems of grass carp (Ctenopharyngodon idella). A total of 35 grass carp, 5-6 cm long were divided into five groups (E0, E1, E2, E3 and E4) having seven fish in each. The fish in group E0 were kept as control in plain water, while those in group E1, E2, E3 and E4 were exposed to 0.75, 1.00, 1.50 and 2.00 ppb of endosulfan in water, respectively for 96 hrs. Water and test chemical solution were renewed daily throughout the experiment. At the end of experimental period blood samples from fish in each group were collected. The morphometric parameters including total weight, length, standard length and organ weights showed non-significant difference. Samples from gills, intestine and liver were collected for the histopathological examination. A significant dose dependent decrease was noted in the leukocyte and erythrocyte counts, while the platelets were higher in the intoxicated fish. The values of Hb and PCV were also significantly lower in the high dosed group. There was fusion and disruption of gills along with severe congestion in the high dosed fish groups. The intestine showed atrophy of villi and increased goblet cells count. The hepatocytes showed degenerative changes including vacuolation, pyknosis etc. It was concluded that use of endosulfan in the water is extremely toxic for the fish health so a strong legislation must be implemented in the developing world as in the analogy of European Union.

Key words: Ctenpharyngodon idella, Endosulfan, Hematology, Histopathology, Pathology