Assessment of ecotoxicological effect of atrazine: Histopathological and ultrastructural evidence of muscle damage in Nile tilapia

In this study the histopathological and ultrastructural effects of atrazine, a widely used herbicide, on the muscle tissue of Nile tilapia (<i>Oreochromis niloticus</i>) were investigated. To evaluate the sublethal effects of this herbicide, <i>O. niloticus</i> individuals were exposed to 0.9 mg/L atrazine (LC50/10) for 21 days, based on the previously reported LC50 value for <i>O. niloticus.</i> Muscle tissue samples were collected on the 7th, 14th, and 21st days of exposure and analyzed using both light and transmission electron microscopy (TEM). Semiquantitative scoring of histopathological lesions revealed a range of atrazine-induced changes in muscle tissue, with increasing severity over time. The most prominent changes included pyknotic nuclei, muscle fiber deformation, and necrosis, indicating cellular membrane disruption and impaired energy metabolism. Ultrastructural analysis by TEM also showed mitochondrial cristolysis, dilation of the sarcoplasmic reticulum, and vacuolar deformation of the sarcoplasm. The results demonstrate that atrazine exposure, even at sublethal concentrations, can cause significant cellular and subcellular damage in the muscle tissue of <i>O. niloticus</i>. This study contributes to a growing body of knowledge on the adverse effects of atrazine on aquatic organisms and emphasizes the importance of monitoring and mitigating atrazine exposure in aquatic environments.