The Role of Extracellular Ca²⁺ in the Activation of Pectinaria Oocytes

Several events are associated with fertilization in oocytes. Two such events are an increase in cytoplasmic Ca 2+ 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 2+ and resumption of meiosis in this species. Meiosis in unfertilized oocytes could be re‐initiated with the divalent cation ionophore, A23187. Oocytes in Ca 2+ free sea water, however, did not resume meiosis in the presence of the ionophore. Furthermore, it was observed that Ca 2+ must be present for at least 15 min following ionophore treatment for meiosis to resume. These results suggest that extracellular Ca 2+ is required for the re‐initiation of meiosis in this species.