Spontaneous maturation of starfish oocytes: Role of follicle cells and calcium ions

Starfish oocytes released from the ovary into sea water during the breeding season underwent spontaneous meiotic maturation. In the absence of calcium ions, follicle cells surrounding the oocyte were dispersed and oocyte maturation did not occur. Immature oocytes in the absence of follicle cells did not mature even when calcium was available. Calcium ions stimulated the release of a meiosis-inducing substance from follicle cells which had been isolated in calcium-free sea water. Increasing numbers of follicle cells produced a parallel increase in the amount of meiosis inducing substance released. Spontaneous oocyte maturation appeared to be initiated and mediated in part by calcium sensitive processes in the follicle cells rather than the oocyte.