Determination of the by geotoxic effect of Thiamethoxam in rainbow trout (Oncorhynchus mykiss) micronucleus test

The micronucleus (MN) test, an indicator of genetic damage accumulated over the lifetime of cells, is one of the most suitable techniques to identify the integrated response to the complex mixture of pollutants. In this study, it was aimed to evaluate the genotoxic effects of Thiamethoxam, a neonicotinoid pesticide widely used in agricultural activities, on rainbow trout, which is a biomarker in toxicological studies in aquatic ecosystems, by micronucleus technique. In the study, 4 groups were formed with two replicates. There were 10 fish in each group and no substance was applied in the control group. Thiamethoxam doses of 25 and 75 mg/l were applied. As a positive control, 10 mg/ benzene was applied. In the application unit, 5000 erythrocytes were counted for each fish from the blood samples taken from the caudal vein after anesthesia and the micronucleus frequency in 1000 cells was determined. Liver tissue was taken after cervical dislocation and evaluated for histopathological analysis. As a result of micronucleus frequency analysis; the average micronucleated erythrocyte rate was 0.3% in the control group, 0.78% in the 25 mg/l Thiamethoxam group, 1.72% in the 75 mg/l Thiamethoxam group and 5.88% in the positive control group treated with 10 mg/l benzene. In histologic examinations of the tissues; while the liver tissue in the control group was observed in normal histologic structure, slight degeneration was observed in the 25 mg/l Thiamethoxam group. In 75 mg/l Thiamethoxam group, degeneration, necrosis areas and steatosis were observed in hepatocytes. In the positive control group, cell infiltration and bile duct degeneration were observed in addition to hepatocyte degeneration, necrosis and steatosis. As a result of the data obtained from the study, it was determined that the dose increase in Thiamethoxam administration led to an increase in the frequency of erythrocytes with micronuclei compared to the control group. In addition, it is also understood that the frequency and severity of lesions seen in the liver tissue increased with the increase in Thiamethoxam dose.