Intergenerational toxicity of 17α-ethinylestradiol (EE2): Effects of parental exposure on early larval development and transcriptomic profiles in the Sydney rock oyster, Saccostrea glomerata

This study exposed adult Sydney rock oysters, of either sex or both, to the synthetic estrogen 17α-ethinylestradiol (EE2) at 50 ng/L for 21 days, followed by an examination of developmental endpoints and transcriptomic responses in unexposed larvae. Reduced survival was observed at 1 day post-fertilisation (dpf) in larvae from bi-parental exposure (F_TM_T). Motile larvae at 2 dpf were fewer from maternal (F_TM_C), paternal (F_CM_T), and F_TM_T exposures. Additionally, shell length at 7 dpf decreased in larvae from F_TM_C and F_TM_T parents. RNA sequencing (RNA-seq) revealed 1064 differentially expressed genes (DEGs) in 1-dpf larvae from F_TM_T parents, while fewer DEGs were detected in larvae from F_TM_C and F_CM_T parents, with 258 and 7, respectively. GO and KEGG analyses showed significant enrichment of DEGs in diverse terms and pathways, with limited overlap among treatment groups. IPA results indicated potential inhibition of pathways regulating energy production, larval development, transcription, and detoxification of reactive oxygen species in F_TM_T larvae. qRT-PCR validation confirmed significant downregulation of selected DEGs involved in these pathways and relevant biological processes, as identified in the RNA-seq dataset. Overall, our results suggest that the intergenerational toxicity of EE2 is primarily maternally transmitted, with bi-parental exposure amplifying these effects.