Several events are associated with fertilization in oocytes. Two such events are an increase in cytoplasmic Ca 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 Ca and resumption of meiosis in this species. Meiosis in unfertilized oocytes could be re-initiated with the divalent cation ionophore, A23187. Oocytes in Ca free sea water, however, did not resume meiosis in the presence of the ionophore. Furthermore, it was observed that Ca must be present for at least 15 min following ionophore treatment for meiosis to resume. These results suggest that extracellular Ca is required for the re-initiation of meiosis in this species.
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