Physiological responses of the female sea urchins Heliocidaris crassispina to sub-chronic bisphenol C exposure

Bisphenol C (BPC), an alternative to bisphenol A, has uncertain effects on marine invertebrate gonads. Female sea urchins ( Heliocidaris crassispina ) were exposed to 0, 2, 4, or 6 μM BPC for 15 d under laboratory conditions at effect-oriented concentrations. Gonadal responses were assessed using histology, biochemical assays, transcriptomics, and metabolomics. H&E staining suggested less compact tissue and fewer visible oocytes in exposed groups, whereas quantitative Oil Red O analysis showed a lower lipid-positive area with increasing BPC concentration. Antioxidant enzyme activities and malondialdehyde levels varied across exposure times and concentrations, consistent with altered redox status and lipid peroxidation at selected time points. Transcriptomic analysis of 15 d control and 6 μM groups identified 1970 upregulated and 1943 downregulated genes (|log₂ fold change| > 1; FDR < 0.05). These genes were enriched in pathways associated with mitochondrial function, DNA replication, lipid metabolism, endocrine regulation, and signal transduction. Untargeted metabolomics identified 196 increased and 204 decreased putatively annotated metabolites, including features mapped to lipid and amino acid metabolism. Integrated analysis showed that differentially expressed genes and metabolites mapped to arachidonic acid metabolism, D-amino acid metabolism, and gap junction pathways. Together, these findings indicate that BPC exposure was associated with changes in gonadal morphology, lipid-positive area, redox-related biomarkers, and molecular profiles. Redox and metabolic changes may be related to the observed tissue alterations, although functional links and reproductive outcomes remain to be tested. Further studies at environmentally relevant concentrations and with direct reproductive endpoints are needed.