Gender-Specific Reproductive Toxicity of Biodegradable Microplastics and Bisphenol F in Medaka (Oryzias latipes)

To investigate the combined effects of exposure to biodegradable microplastics (MPs) and bisphenol substitutes in aquatic organisms, this study selected polylactide (PLA) as a representative biodegradable MP and polyethylene terephthalate (PET) as a conventional non-biodegradable counterpart. Adult medaka (Oryzias latipes) were exposed to environmentally relevant concentrations of MPs (20 μg·L^-1) and bisphenol F (BPF, 2 μg·L^-1). Behavioral performance was evaluated, with a particular focus on reproductive toxicity. Co-exposure of PLA or PET with BPF significantly impaired swimming performance, and the inhibitory effect was stronger in the PLA group. Importantly, reproductive assessments revealed clear sex-specific responses. PLA and BPF co-exposure primarily affected females and induced ovarian cell apoptosis and degenerative alterations; In contrast, PET and BPF co-exposure caused more pronounced structural damage in male testes. These findings reveal the gender-specific reproductive toxicity induced by combined exposure to biodegradable MPs and bisphenol substitutes, and provide a scientific basis for the ecological risk assessment of biodegradable MPs.