Haematological, biochemical, enzymological changes and mitochondrial dysfunction of liver in freshwater climbing perch Anabas testudineus during their acute and chronic exposure to sodium fluoride.

Anthropogenic activities are increasing fluoride concentration in watercourses. The present study focuses on the sublethal toxicity of sodium fluoride during sub-chronic and chronic time periods in the freshwater fish Anabas testudineus. The 96-hour LC value for fluoride was found to be 616.50 mg/L. Excessive mucous production and hyper excitability, followed by loss of balance, were seen in fish under acute fluoride exposure. Significant reduction in yield and specific growth rate of fish were assessed at 15, 30 and 45-days exposure intervals. Different bio-indicators like Hepatosomatic-index, Gonadosomatic-index and fecundity were reduced significantly in fish exposed to 10% (61.6 mg/L) and 20% (123.2 mg/L) of 96 h of LC values of fluoride in comparison to control. Toxicant concentrations directly correlated with parameter lowering. Fluoride exposure increased plasma glucose, creatinine, AST, and ALT and reduced total RBC, haemoglobin content, Hct (%), plasma protein, and cholesterol. Moreover, fluoride exposure significantly reduces the mitochondrial membrane potential in liver. This may result in metabolic depression, haematological, biochemical, and enzymological stress. The in-silico structural analysis predicts that fluoride may impede cytochrome c oxidase of the electron transport system, hence inhibiting mitochondrial functionality. These findings collectively highlight the urgent need for stringent regulation and monitoring of fluoride levels in freshwater ecosystems, as the subchronic and chronic effects observed in A. testudineus may have broader implications for aquatic ecosystems.