Sub‐Chronic Bisphenol‐A Toxicity in Climbing Perch, <scp> <i>Anabas testudineus</i> </scp> : Insight Into Metabolic Disruption, Oxidative Stress, and Histopathological Changes

In the present era of climate change, pollution has become a threat to the growth and sustainability of aquaculture and fisheries. The widespread occurrence of microplastics across ecosystems is particularly concerning, as it affects the entire food chain-from lower to higher trophic levels, including fisheries, and it is an important source of plasticizers (bisphenol-A, BPA) in the aquatic environment. Therefore, to understand the physiological effects of BPA, an experiment was conducted to understand the effect of sublethal doses of BPA on immune-physiological and histopathological changes in the climbing perch, Anabas testudineus (average weight: 22 ± 3 g and total length: 10 ± 2 cm). Median lethal concentration (96 h-LC₅₀) was determined by using BPA concentrations of 12.50, 13.00, 13.50, 14.00, 14.50, 15.00, 15.50, 16.00, 16.50, 17.00, 17.50, 18.00, and 18.50 ppm. The estimated 96 h-LC₅₀ of BPA was 16.77 ppm. Sublethal doses of BPA viz. 0.419, 0.838, and 1.677 ppm were evaluated for their effects on immune-physiology, oxidative stress, and histopathology. Compared to control, the BPA-exposed group showed significantly higher erythrocyte and leucocyte counts, and oxidative stress (superoxide dismutase and catalase) and protein metabolic enzymes (aspartate aminotransferase and alanine aminotransferase) activity in the liver, whereas acetylcholinesterase was significantly inhibited in brain tissue (p < 0.05). Exposure to BPA also significantly enhanced stress biomarkers viz. serum glucose and HSP (p < 0.05). In addition, upregulation of HSP, iNOS, CAS 3a, and CYP450 and downregulation of TNFα and Ig genes were recorded. The study concluded that even a low dose of BPA (0.419 ppm) severely affects the stress biomarkers of A. testudineus.