MESSENGER. “Ca2+ is important as an intracellular second messenger in the fertilization of many organisms. In animals including mouse, xenopus, ascidian, starfish and sea urchin, various patterns of cytosolic Ca2+ waves and oscillations are involved in fertilization and the subsequent onset of embryogenesis.”
http://www.nature.com/articles/ncomms5722?WT.ec_id=NCOMMS-20140829