ON THE ROLE OF CALCIUM IONS IN OOCYTE MATURATION IN THE POLYCHAETE CHAETOPTERUS PERGAMENTACEUS*

Publisher Website
Google Scholar
Abstract
The germinal vesicle of mechanically released Chaetopterus oocytes disintegrates in natural sea water (NSW), but not in artifical sea water of normal composition (ASW), Ca-free sea water (CaFSW), Mg-free salt water (MgFSW) or Ca and Mg-free sea water (CaMgFSW). Several methods of inducing oocyte maturation using chemically well-defined media were established. Germinal vesicle breakdown was induced by the treatment of immature oocytes with KCl (60 mM) in ASW or MgFSW. The presence of Ca2+ was necessary for inducing oocyte maturation with high K concentration. Differentiation without cleavage was observed after this treatment. Trypsin (0.3%) induced oocyte maturation in ASW, but not in CaFSW. Oocytes matured in this manner developed to trochophores upon insemination. Immature oocytes treated with isotonic CaCl2 for less than 1 min and then transferred to ASW, underwent germinal vesicle breakdown. The oocytes were arrested at the 1st meiotic metaphase and upon insemination developed to trochophore larvae. Tetracaine (0.4 mM) induced oocyte maturation in the absence of Ca2+ in the medium. In ASW, CaFSW or CaMgFSW containing the drug, oocytes were arrested at the 1st meiotic metaphase, while in MgFSW with tetracaine they developed parthenogenetically up to the 4- and 8-cell stages. The role of Ca in oocyte maturation was established and its importance discussed based on results obtained with different ways of inducing oocyte maturation.