Life-Cycle Benzo[a]pyrene Exposure Induces Sex-Specific Reproductive Impairment, Feminization, and Transgenerational Disruption in Marine Medaka (Oryzias melastigma)

Benzo[a]pyrene (BaP), a widespread environmental pollutant, has been extensively studied; however, knowledge gaps remain regarding its sex-specific reproductive toxicity and the persistence of its transgenerational effects. Marine medaka (Oryzias melastigma) were exposed to environmentally relevant BaP concentrations (1, 4, and 8 μg/L) throughout the F0 generation, with transgenerational effects assessed in F1, F2, and F3 generations reared in clean seawater. BaP exposure significantly affected biometric responses and reproductive parameters, including impaired gametogenesis, reduced fecundity, and decreased fertilization rates. Males were more sensitive to oxidative stress and hormonal imbalances in the gonads and showed delayed recovery during depuration. Genes in the hypothalamus-pituitary-gonad-liver (HPGL) axis were disrupted in a sex-specific manner. A persistent feminization and poor egg quality were observed up to the F2 generation, indicating transgenerational endocrine disruption. Despite recovery initiation in F3, the results reveal persistent sex-specific reproductive toxicity, emphasizing the need to assess sex-specific and transgenerational effects in ecotoxicology.