Endosulfan is an important environmental pollutant that is a pesticide of organochlorine. The 24, 48, 72 and 96h median lethal concentrations of endosulfan (35 EC) were assessed by an acute static renewal test. The sublethal concentration taken for the present study is one-tenth of the 96h LC₅₀ and fish were exposed to that concentration (1.69 ppb) for 30 days. The histopathological observations revealed the presence of catecholamine neurons in the optic tectum and severe depletion of the layer stratum grisum periventricular. An altered pattern of neurons as an “interrupted string of pearls” was noticed in the posterior tuberal nucleus. From the present study, we could conclude that endosulfan is a serious toxicant that even affects the vital organs like the brain of vertebrates. Histology of the spleen showed necrosis in red pulp, hyperplasia and exudate in white pulp and an increased number of melanomacrophage centers (MMC) of the exposed fish species. Based on the results of this study, it is concluded that endosulfan is highly toxic to edible freshwater fish Anabas testudineus. Subsequently, damage to the structures of cells and tissues and histopathology of target organs comprise a significant parameter to be considered in evaluating the toxic possibility of contaminations on living organisms in various environmental conditions and represent the time exposure to which organisms are subjected.

freshwater teleost, endosulfan, brain histopathology, spleen histopathology