Histopathological and Cytopathological Determination of Alterations and Immune Response in Spleen Tissue of Oreochromis Niloticus Exposed to Sub-Lethal Concentration of Diazinon

Abstract In this study, it was aimed to determine duration based histopathological, cytopathological and immunological alterations in spleen structure of Oreochromis niloticus samples exposed to sublethal concentration of diazinon standart with light microscope and TEM. At the first step of the study, the fish were exposed to 280 µg/L (LC50/10) Diazinon for 21 days. Afterwards, the histopathological, cytopathological alterations and immune response in the spleen tissue were investigated by light microscope and TEM at 7th, 14th and 21st days. In the histopathological results, melanomacrophage centers with hemosiderin accumulation, cloudy swelling, pyknosis, hypertrophy and necrosis were detected in the spleen tissue. The severity of these alterations increased with the duration of the exposure. Mitochondrial deformation (cristolysis), pyknotic nucleus, vacuolation, increased phagositic activity of melanomacrophage, nuclear deformation, high amount of melanin and hemosiderin accumulation were detected in the cytopathological investigation of spleen tissue. According to those results it could be assumed that diazinon caused histopathological and cytopathological alterations in the spleen tissue of O. niloticus and also had immunotoxic effects.