G-protein coupled estrogen receptor (GPER) inhibits final oocyte maturation in common carp, Cyprinus carpio.

•GPER mRNA and protein are present in oocytes, not in follicle cells of C. carpio.•Both GPER mRNA and protein expressed maximally at late-vitellogenic oocyte.•E2 treatment inhibited spontaneous and 17,20β-P-induced oocyte maturation.•Follicle cells removal increased spontaneous OM, that was reversed by E2 treatment.•E2-induced cAMP production in oocyte was reversed by 17,20β-P treatment.