1-METHYLADENINE PRODUCTION BY OVARIAN FOLLICLE CELLS RESPONSIBLE FOR SPAWNING IN THE STARFISH ASTERINA-PECTINIFERA

Resumption of meiosis in starfish oocytes is induced by 1-methyladenin e (1-MeAde) produced by ovarian follicle cells under the influence of gonad-stimulating substance (GSS). It has also been reported that 1-Me Ade induces follicular envelope breakdown (FEBD), releasing oocytes fr om the ovaries; i.e., spawning. This study was undertaken to determine whether the amount of 1-MeAde produced by follicle cells is enough to induce germinal vesicle breakdown (GVBD) and FEBD in the starfish Ast erina pectinifera. After incubation of an ovary with GSS at concentrat ions of more than 0.05 mg/ml for about 20 min, spawning started. Almos t the same period of time was required for spawning after treatment wi th 0.1 muM 1-MeAde. However, continuous treatment with GSS was not nec essary, and about 5 min of GSS application was sufficient for inductio n of spawning. Each oocyte is surrounded by a follicular envelope cons isting of about 50 cells. 1-MeAde production by isolated follicle cell s started immediately upon GSS stimulation, and the amount of I-MeAde produced in vitro was correlated with the number of follicle cells pre sent. Thus, 50 follicle cells were shown to produce about 1.1 fmol 1-M eAde during 5 min of GSS treatment. These results confirm that the amo unt of 1-MeAde produced by follicle cells is sufficient for meiosis in itiation and release of oocytes in starfish.