The role of chorion around embryos in toxic effects of bisphenol AF exposure on embryonic zebrafish (Danio rerio) development

Abstract

Bisphenol AF (BPAF) has been found ubiquitously in the environment and attributed to the population degradation of the fish community. It was proved that the susceptibilities of fish to BPAF exposure are diverse in different developing stages. However, the role of embryonic chorion under BPAF exposure remains unknown. In the study, model organism zebrafish (Danio rerio) was adopted to carry out the embryo acute toxicity tests (OECD No. 236) combined with microinjection (MI, at the blastula) and dechorionation (DC, at the pharyngula) techniques and non-treatment (NT-1, NT-2) for investigating the role of chorion around embryos. The results showed that the BPAF exposure could considerably contribute to the growth-retardation, delayed hatching, pericardial edema, yolk sac edema, non-inflated swimming bladder and death. The embryos in the MI-ZR group which soaked to ZR embryo medium after microinjected with BPAF solutions were hardly affected. While the mortalities and malformation rates in the MI-BPAF (the embryos were injected with BPAF and soaked in BPAF solution) and NT-1 (the embryos were not injected but soaked in BPAF solution) increased significantly with time and dose. Under BPAF soaking exposure, the dechorionated embryos in the DC (the embryos were dechorionated and soaked in BPAF solution) were significantly sensitive in comparison with the parallel undechorionated embryos in the NT-2 (the embryos were not dechorionated but soaked in BPAF solution). The 96 h LC50 values of MI-BPAF, NT-1, DC and NT-2 were 1.61, 1.68, 0.27, 1.30 mg L−1, respectively. The results indicate that the chorion has good permeability for BPAF passing through it at the earlier stage of zebrafish embryonic development, but becomes an effective barrier for protecting embryos over time. Moreover, zebrafish are more sensitive to BPAF exposure at embryos-to-larvae development. Thus, BPAF exposure hazards the development of zebrafish embryos and larvae. Waterborne BPAF exposure might pose serious risks to aquatic organisms and break the balance of aquatic ecosystem.