Dose- and Duration-Dependent Biochemical Toxicity of Lead in an Endangered South Asian Freshwater Fish (Tor putitora)

Résumé

Heavy metal contamination poses a serious threat to freshwater biodiversity, particularly to endangered fish species inhabiting polluted aquatic ecosystems. Lead (Pb), a persistent and highly toxic metal, is widely distributed in aquatic environments and can induce profound physiological disturbances in exposed organisms. The present study investigated the dose- and duration-dependent biochemical effects of Pb exposure in the endangered golden mahseer (Tor putitora), a species of high ecological and conservation value in South Asia.

Healthy fish (70–80 g) were exposed to sublethal concentrations of lead nitrate under controlled laboratory conditions. Acute exposure trials were conducted for 7, 14, and 21 days (55, 45, and 35 mg L⁻¹, respectively), while chronic exposure trials extended to 35, 49, and 63 days (25, 15, and 5 mg L⁻¹, respectively). Serum biochemical parameters, including alanine transaminase (ALT), aspartate transaminase (AST), lactate dehydrogenase (LDH), creatinine phosphokinase (CPK), total protein, cholesterol, and triglycerides, were analyzed to evaluate systemic toxicity.

Results revealed a significant elevation in ALT, AST, LDH, and CPK activities, accompanied by alterations in lipid metabolism and a reduction in total protein levels. These effects were more pronounced during chronic exposure, indicating progressive physiological impairment with prolonged Pb accumulation. The findings demonstrate a clear duration-dependent toxicological response, with chronic Pb exposure producing more severe biochemical disruptions than acute exposure.

This study highlights the sensitivity of T. putitora to lead toxicity and underscores the utility of biochemical biomarkers for monitoring heavy metal stress in endangered freshwater fish. The results provide valuable insights for environmental risk assessment and conservation management in Pb-contaminated freshwater ecosystems.