Individual and Combined Effects of Bisphenol A and Lithium on the Regenerative Capacity of the Polychaete Hediste diversicolor.

Bisphenol A (BPA) and lithium (Li) are emerging contaminants widely detected in aquatic environments, yet their effects on regenerative processes remain poorly understood. This study evaluated the effects of BPA, Li, and their mixture on the regenerative capacity of the estuarine polychaete Hediste diversicolor, an important bioturbator in coastal ecosystems. Organisms were exposed for 21 days to BPA (0-135 μg/kg), Li (0-78.13 mg/kg), and BPA + Li mixtures under controlled laboratory conditions. Regeneration was assessed by determining the number of regenerated segments and the percentage of body width following posterior amputation. Results showed that BPA reduced regenerative capacity across all treatments, with the strongest effects observed at 5 and 45 μg/kg. Li exposure also decreased regeneration, particularly at 12.5 mg/kg. Combined exposure also resulted in reduced regenerative capacity, with the strongest effect observed at 12.5 mg/kg Li + 45 μg/kg BPA. Regeneration in mixture-exposed organisms was generally comparable to that observed following individual exposures. Notably, organisms exposed to 12.5 mg/kg Li and 5 μg/kg BPA individually had lower regenerative capacity than the corresponding mixture treatment, suggesting that co-exposure did not exacerbate the effects observed under individual exposures. Overall, BPA and Li negatively affect regeneration in H. diversicolor, highlighting regeneration as a sensitive endpoint for ecotoxicological assessment.