Calcium signals and oocyte maturation in marine invertebrates
Published: 19 November 2015
Ryusaku Deguchi1, Noriyo Takeda2 and Stephen A. Stricker*,3
1Department of Biology, Miyagi University of Education, Sendai, Miyagi, Japan, 2Research Center for Marine Biology, Graduate School of Life Sciences, Tohoku University, Asamushi, Aomori, Japan and 3Department of Biology, University of New Mexico, Albuquerque, NM, USA
In various oocytes and eggs of animals, transient elevations in cytoplasmic calcium ion concentrations are known to regulate key processes during fertilization and the completion of meiosis. However, whether or not calcium transients also help to reinitiate meiotic progression at the onset of oocyte maturation remains controversial. This article summarizes reports of calcium signals playing essential roles during maturation onset (=germinal vesicle breakdown, GVBD) in several kinds of marine invertebrate oocytes. Conversely, other data from the literature, as well as previously unpublished findings for jellyfish oocytes, fail to support the view that calcium signals are required for GVBD. In addition to assessing the effects of calcium transients on GVBD in marine invertebrate oocytes, the ability of maturing oocytes to enhance their calcium-releasing capabilities after GVBD is also reviewed. Furthermore, possible explanations are proposed for the contradictory results that have been obtained regarding calcium signals during oocyte maturation in marine invertebrates.