Multi-level toxicity assessment of sub-lethal mercury exposure in Clarias batrachus
摘要
The occurrence of xenobiotics in the environment consistently poses a potential threat to biological organisms. This study was designed to test the hypothesis that mercury (Hg) acts as a systemic neuro- and metabolic toxin, inducing dose- and time-dependent disruptions in behavioral and physiological homeostasis that are rooted in specific molecular interactions. The toxicological responses of Clarias batrachus were evaluated following acute exposure to eight mercury concentrations (0.0–0.90 mg/L) over 24, 48, 72, and 96 h. Experimental endpoints included environmental risk assessment, respiratory performance, behavioural responses, and feeding activity. The experimental results revealed that Hg exposure caused a significant (p < 0.05) dose- and time-dependent reduction in oxygen consumption, accompanied by marked behavioural alterations, including hyperactivity, impaired swimming performance, and loss of equilibrium. Feeding rate was significantly reduced in exposed fish. Correlation analysis revealed positive associations between oxygen consumption and mortality, whereas abnormal locomotion, mucus secretion, and impaired postural control showed negative correlation trends. Parallel to these findings, predictive in silico analysis was performed, identifying two putative Hg2⁺ coordination regions in the Hsp90 chaperone protein of C. batrachus, located in the N-terminal (Lys203-His204) and C-terminal (Cys591-Cys592) domains, which may interfere with ATP binding and dimer stability. Overall, the findings demonstrate that integrated behavioural and physiological endpoints provide a robust assessment of mercury toxicity in fish, while in silico results offer predictive insights into potential molecular mechanisms.