PRELIMINARY-OBSERVATIONS ON OOCYTE MATURATION AND OTHER ASPECTS OF REPRODUCTIVE-BIOLOGY IN CAPTIVE FEMALE SNOOK, CENTROPOMUS-UNDECIMALIS

Female snook collected from the field in mornings during the summer mo nths appear to have asynchronous ovaries, with ovarian follicles gener ally present in all developmental stages up to prematurational stages. Methods were developed to maintain snook ovarian follicles successful ly in culture for up to 48 h at 28-degrees-C. Oocytes within follicles larger than 0.5-mm diameter could be induced to undergo maturation (g erminal vesicle breakdown, clarification, volume enlargement by 200%) in vitro with suitable concentrations of either human chorionic gonado tropin or homologous pituitary extract. Snook pituitaries were found t o contain approximately 155 IU gonadotropic activity/mg. Steroids that have been found to be effective inducers of oocyte maturation in othe r teleosts were essentially ineffective on snook oocytes, so the endog enous maturation-inducing steroid produced by follicles under gonadotr opic stimulation remains unknown. After capture, snook ovarian follicl es could be used successfully for experimental purposes for up to 48 h , after which they became unresponsive to gonadotropin in vitro. Conco mitant with the decline in follicle competence, rapid and massive dege nerative changes occurred in the ovary, which was invaded by a large p opulation of PAS-positive cells.