Simultaneous Germinal Vesicle Migration and Oil Droplet Coalescence Predict Final Oocyte Maturation in the Leopard Grouper

AbstractThe size of oocytes during germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) was revised for the Leopard Grouper Mycteroperca rosacea. Histology of ovaries, plasma levels of estradiol-17s (E2), and testosterone (T) were analyzed in Leopard Grouper at 0, 12, 16, and 24 h after a priming dose of 1,000 IU/kg body weight of human chorionic gonadotropin (hCG) and were compared with control females injected with saline solution. Histological observations were verified in hormonally induced females by observing in vivo intraovarian biopsies after using the same priming dose and a second resolving dose of 500 UI/kg body weight of hCG 16 or 24 h later, which served to analyze spawning performance. Histological and in vivo intraovarian biopsies showed that in full-yolk oocytes (~455 μm diameter) GVM and GVBD were concomitant with coalescence of a single oil droplet 16 and 24 h after the first injection. The oil droplet became a morphological marker as well as a predicting indicator of t...