Behavioural toxicity and respiratory distress in early life and adult stage of walking catfish Clarias batrachus (Linnaeus) under acute fluoride exposures

Objective Toxicant-induced behavioural changes reflect underlying physiological deficiencies that can be utilized to predict ecological risks. The present investigation was undertaken to determine the toxic impact of sodium fluoride on the juvenile and adult size group of Clarias batrachus (Order: Siluriformes; Family: Clariidae). Methods To determine the LOEC, NOEC, and MATC for both size groups alongside the 96h lethal concentration (LC50), exposure concentration of sodium fluoride i.e., 180, 200, 220, 240, 260, 280, 300, 320, 340, 360 and 380 mg/l for juvenile fish and 340, 360, 380, 400, 420, 440, 460, 480, 500 and 520 mg/l for adult fish were used. The 96h (LC50) for both size groups were found to be 277.023 and 433.605 mg/l respectively. Safe-level exposures of fluoride to fish was also estimated to determine the ecological risk assessment for the fish. Results Ethological responses i.e., air gulping, body orientation, swimming, hyperactivity, mucus secretion, body balance, and colour and schooling tendency, etc. varied across life-stages. Adults exhibited more adaptive behavioural responses compared to juveniles with elevated exposures. Buccal and opercular movements of the exposed fish were significantly higher than the control group, with a higher oxygen consumption rate at elevated fluoride exposures. Conclusion Study findings highlight the potential of elevated fluoride levels in the environment to elicit varied behavioural responses in adult and early-staged fishes, thus increasing risks of disrupted adaptive capacity and the likelihood of significant mortality in the wild. Life-stage specific responses to fluoride exposures implicate under-developed organ-system, physiology and morphology in juveniles compared to adults.

Automated summary

Toxicant-induced behavioural changes reflect underlying physiological deficiencies that can be utilized to predict ecological risks. The present investigation on the toxic impact of sodium fluoride on Clarias batrachus found that adult fish exhibited more adaptive responses compared to juveniles with elevated exposures, with higher oxygen consumption rates. Life-stage specific responses to fluoride exposures implicate under-developed organ-system, physiology and morphology in juveniles compared to adults.