Disruption of gonadal steroidogenesis and reproductive function in Gambusia affinis after chronic exposure to environmentally relevant and sublethal concentrations of carbamazepine.

Pharmaceutical contaminants are increasingly recognized as critical pollutants in aquatic ecosystems, with antiepileptic drugs such as carbamazepine (CBZ) frequently detected at environmentally relevant concentrations. This study evaluated the reproductive and endocrine-disrupting effects of CBZ in male and female Gambusia affinis. Fish were exposed to environmentally relevant (13 ng L-1) and sublethal concentrations (2.4 and 4.8 mg L-1) for 60 days. Reproductive indices, including gonadosomatic index, sperm quality parameters, fecundity, oocyte diameter, and histopathology, were assessed alongside hormonal variations (FSH, LH, testosterone, estradiol, cortisol), vitellogenin levels, and the concentrations of steroidogenic enzymes (3β-HSD, 17β-HSD, and aromatase). Results demonstrated that sublethal concentrations of CBZ significantly reduced sperm count, motility, and viability in males, while also decreasing fecundity and oocyte development in females. Hormonal disruption was evident, with decreased levels of FSH, LH, and testosterone in males and estradiol in females, alongside elevated cortisol. CBZ exposure increased aromatase and vitellogenin in males while reducing both in females, indicating feminization in males and impaired ovarian function in females. Histopathological alterations corroborated these findings, showing gonadal degeneration under chronic exposure. These results confirm that CBZ, even at low concentrations, poses a substantial risk to fish reproduction and endocrine homeostasis. The study highlights the necessity of monitoring pharmaceutical residues in freshwater ecosystems and their implications for fish population dynamics and ecological sustainability.