Exposure-Recovery Approach for Hepatic Toxicity Analysis of Pyrethroid Lambda-Cyhalothrin: Histopathological, Histochemical, and Biochemical Responses in Oreochromis niloticus.

Abstract

Lambda-cyhalothrin is a synthetic pyrethroid insecticide widely used in agriculture, but its potential to contaminate aquatic ecosystems and exert high toxicity on fish at low concentrations raises ecotoxicological concerns. While standard histopathological and biochemical assessments are common, the novel integration of pigment-based biomarkers (hemosiderin and lipofuscin) offers unexplored mechanistic insights into tissue resilience and residual oxidative stress during postexposure recovery. This study evaluated liver changes (degree of tissue changes-DTC), pigment deposition, and biochemical profiles in Oreochromis niloticus exposed to sublethal lambda-cyhalothrin (1.24 μg L-1) for 3, 7, and 14 days, followed by a 15-day recovery phase. Exposure induced a progressive, time-dependent increase in DTC, transitioning from early reversible inflammatory/vascular lesions to irreversible parenchymal and hepatopancreatic necrosis by Day 14. This structural decline correlated with significant elevations in serum ALT and AST activities. Critically, exposed fish exhibited a sharp increase in hepatic hemosiderin and lipofuscin. Following the 15-day recovery period, lipofuscin levels and GGT activity normalized, reflecting immediate metabolic detoxification. However, elevated DTC, serum transaminases, and prominent hemosiderin deposits persisted. By tracking distinct temporal trajectories, our unique multibiomarker approach demonstrates that while immediate oxidative metabolic stress subsides after exposure ceases, iron dysregulation and structural liver damage remain unresolved. These findings emphasize that standard recovery windows in clean water are insufficient to fully restore tissues, highlighting hidden ecological risks for fish farming and wild populations exposed to pulses of agricultural runoff.