Histopathological Changes and Antioxidant Enzymes as Biomarkers for Monitoring the Health of Fish Cyprinus carpio L.

The current study focused on monitoring the health of Cyprinus carpio (common carp) to assess the health of fish in aquatic environment. The study was designed to include various environmental conditions. Four groups were involved in this study: a control group, a group treated with thyme oil, a group treated with cadmium chloride, and a group exposed to thyme oil and cadmium chloride. The antioxidant levels (glutathione peroxidase and catalase) in gills and muscles were measured at intervals over 30 days. Histological examinations were performed to detect any pathological changes in gills and liver resulting from treatments at 3, 7, 15, and 30 days. Exposure to cadmium chloride induced progressive pathological changes, including gill deformities, lamellar adhesion, and epithelial hyperplasia, as well as hemorrhage, degeneration, and necrosis in the liver. The addition of thyme oil to the fish diet, however, mitigated these alterations in both the gills and liver. The results showed significant variations in GPX1 and catalase activity across treatments. Cadmium chloride increased GPX1 and catalase activity in the liver, gills, and muscles, while thyme oil modulated these effects, with muscle tissue exhibiting the highest activity, especially in cadmium-exposed groups. The results demonstrated that these indicators effectively evaluated fish health, providing effective insights for maintaining fish health in the aquatic environment. It was also observed that good aquatic environmental health is not always associated with high levels of antioxidants as a result of pollution. Periodic monitoring of antioxidant levels is recommended to ensure the health of the aquatic environment.