Calcium signaling and endoplasmic reticulum dynamics during fertilization in marine protostome worms belonging to the phylum Nemertea

Metaphase-I-arrested eggs of marine protostome worms in the phylum Nemertea generate a series of point-source calcium waves during fertilization. Such calcium oscillations depend on inositol-1,4,5-trisphosphate-mediated calcium release from endoplasmic reticulum (ER) stores that undergo structural reorganizations prior to and after fertilization. This article reviews fertilization-induced calcium transients and ER dynamics in nemertean eggs and compares these topics to what has been reported for other animals in order to identify unifying characteristics and distinguishing features of calcium responses during fertilization across the animal kingdom.