The Role of Extracellular Ca

Several events are associated with fertilization in oocytes. Two such events are an increase in cytoplasmic Ca2+ concentration and the resumption of meiosis. Oocytes of the marine annelid, Pectinaria gouldii, are in metaphase I arrest when they are spawned. In this report we investigate the relationship between Ca2+ and resumption of meiosis in this species. Meiosis in unfertilized oocytes could be re-initiated with the divalent cation ionophore, A23187. Oocytes in Ca2+ free sea water, however, did not resume meiosis in the presence of the ionophore. Furthermore, it was observed that Ca2+ must be present for at least 15 min following ionophore treatment for meiosis to resume. These results suggest that extracellular Ca2+ is required for the re-initiation of meiosis in this species.