Acute toxicity of chlorpyrifos at 3, 4, 5, 6, 7, 8 and 9 µg/ L concentrations in Etroplus maculatus was investigated on different tissues for 96 h and the weights of organs exposed to the toxicant showed a significant decrease above 6 µg/ L concentrations when compared to control groups. Histopathological alterations on gill, liver, kidney and spleen were examined and compared with the control groups. Marked histological changes observed in gill were absence of secondary lamellae, necrosis, epithelial lifting, and aneurism. Hepatocytes showed necrosis, vacuolization, anucleated cells and eosinophilic materials in the cytoplasm. Leisons in kidney were necrosis as well as dialation of renal tubules and pyknotic nucleus whereas necrosis, anucleated cells, large numbers of melanomacrophage centers and vacuolization were prominent in spleen tissue. These findings represent the negative impact of chlorpyrifos on cichlid fish, Etroplus maculatus.
