Morphological changes and competence of maturing oocytes in the protandrous black porgy, Acanthopagrus schlegeli.

porgy, Acanthopagrus schlegeli. Females were injected with 2 successive doses of LHRH analog (10 and 50 µg per fish) on days 0 and 1. The oocytes were obtained at 6- or 3-h intervals from the genital pore after treatments. Morphological changes during oocyte maturation and ovulation were observed, and oocyte diameters in in vitro culture (with or without hormones) were measured. Oocyte maturation and ovulation occurred at 20-28 h and 3660 h after the 2nd LHRH-A injection, respectively. It took 4-8 h to complete the process of oocyte maturation (in vivo) and 40 min for ovulation (in vitro). Hormones (17,20β-dihydroxy-4-pregnen-3-one, 17,20β,21-trihydroxy-4pregnen-3-one, and HCG) could significantly induce oocyte maturation in oocytes collected at 9 and 6 h prior to the occurrence of germinal vesicle breakdown (GVBD). Oocyte maturation spontaneously occurred in oocytes collected at 3 h prior to GVBD. HCG showed no synergistic effects with steroids in the induction of oocyte maturation.