Thiamethoxam at sublethal concentrations induces histopathological, serum biochemical alterations and DNA damage in fish (Labeo rohita)

Abstract

The effects of thiamethoxam neonictinoids insecticide (TMX) commonly used in different food crops and in veterinary practice were evaluated in freshwater fish exposed to sublethal concentrations for 120 h. A total of 60 freshwater fish Labeo rohita were collected from local fish rearing center and kept in different five equal groups (A–E). Fish in groups B–E were exposed to sublethal concentrations of thiamethoxam (0, 0.5, 1.0, 1.5, and 2.0 mg/L) to determine the genotoxic potential and serum biochemical effects. Results showed significantly (p<.05) increased concentrations of urea and creatinine in thiamethoxam-treated fish as compared to untreated control fish. The concentrations of liver function tests (aspartate aminotransferase, aspartate aminotransferase, and alkaline phosphatase), cardiac functions tests (cholesterol, triglycerides), and lipid peroxidation product (malondialdehyde concentrations) were significantly increased while serum total proteins and globulin significantly (p<.05) decreased in thiamethoxam exposed fish. Furthermore, blood DNA contents significantly increased in thiamethoxam treated fish. At histopathological level, fatty infiltration, congestion, disruption and degenerations of bile ducts, abnormal sinusoids, nuclear fragmentation, condensation, and eccentric nuclei were observed in liver of thiamethoxam treated fish. Histological observation of kidneys of treated fish showed edema, degeneration of renal tubules, congestion, necrosis of renal tubular cells, glomerular degeneration, and detachment of tubular epithelium. DNA damage by comet assay was significantly increased in hepatocytes, kidneys, and blood cells. In conclusion, the results of our study indicate that thiamethoxam induces blood biochemical, genotoxic, and histopathological alterations in exposed fish.