Sublethal λ-Cyhalothrin Exposure Induces Oxidative Stress and Genotoxicity in the Freshwater Fish Channa punctatus

Abstract

λ-Cyhalothrin is a widely used type II synthetic pyrethroid that can pose a significant risk to non-target aquatic organisms. The present study investigated the sublethal effects of λ-Cyhalothrin on oxidative stress and genetic integrity in the freshwater fish Channa punctatus. Healthy fish were acclimatised for one month and randomly allocated into five groups (n = 10): negative control, cyclophosphamide-positive control (4 mg/L), and λ-Cyhalothrin low (0.495 µg/L), medium (0.990 µg/L), and high (1.980 µg/L) exposure groups. The selected concentrations represented 1/16th, 1/8th, and 1/4th of the reported 96-h LC₅₀ of 7.92 µg/L. Fish were exposed for 7 days under semi-static conditions with daily renewal and re-dosing. Lipid peroxidation, reduced glutathione, and superoxide dismutase were evaluated in blood and liver, while micronucleus and alkaline single-cell gel electrophoresis (comet) assays were performed using peripheral erythrocytes. λ-Cyhalothrin exposure produced concentration-dependent oxidative imbalance, characterised by increased LPO and depletion of GSH and SOD in both blood and liver. Blood LPO increased by 56.96506.33%, whereas GSH and SOD decreased by 11.11–33.33% and 6.64–26.17%, respectively. Hepatic LPO increased by 70.48462.86%, accompanied by reductions of up to 32.69% in GSH and 31.90% in SOD. MN frequency increased from 0.065% in controls to 0.24%, 0.46%, and 0.93% at low, medium, and high concentrations, respectively. Similarly, comet assay parameters demonstrated progressive DNA damage, with tail length and olive tail moment increasing by up to 662.08% and 344.30%, respectively. Overall, the findings demonstrate that 7-day sublethal λ-Cyhalothrin exposure induces pronounced oxidative stress and concentration-dependent chromosomal and DNA damage in C. punctatus, supporting the use of integrated biochemical and genotoxic biomarkers for assessing pesticide toxicity in freshwater fish