Figure 2. Schematic potential models of the signaling in egg activation of the monospermic frog, Xenopus (A), or of the polyspermic newt, Cynops (B). 1. Reproduction. 2012 Jul;144(1):11-22. doi: 10.1530/REP-12-0104. Epub 2012 May 25. Egg activation in physiological polyspermy. Iwao Y(1). Author information. Abstract. Fertilization is indispensable not only for restoring diploid genomes but also for the initiation of early embryonic cell cycles in sexual.
Egg Activation in Polyspermy: Its Molecular Mechanisms and Evolution in Vertebrates. In amphibians, most urodeles (newts) exhibit polyspermy physiologically, but primitive urodeles (Hynobius) and anurans (frogs) exhibit monospermy. Several fertilizing sperm induce multiple small Ca. Ca. 2+ wave occurs in the monospermic egg.
The Ca. 2+ waves in newt eggs are caused by a sperm- specific citrate synthase localized outside the mitochondria. The single Ca. 2+ wave at monospermy is necessary for eliciting a fast block to polyspermy, whereas the small multiple Ca.
Physiological polyspermy seems to be evolved in association with the increase in size of eggs in urodeles, reptiles, and birds laying larger yolky eggs. The sperm factor (citrate synthase) operating in slower egg activation in polyspermic eggs is already prepared in the monospermic urodele Hynobius.
We have focused on comparative studies in fertilization among amphibians to understand the role of egg activation in establishment of polyspermy with discussion of the evolution in vertebrates.
Egg Activation in Polyspermy: Its Molecular Mechanisms and Evolution in Vertebrates. for understanding the evolution in egg activation and polyspermy blocks in. . Its Molecular Mechanisms and Evolution in. 15 Egg Activation in Polyspermy: Its Molecular Mechanisms and. Egg activation in physiological polyspermy. In biology, polyspermy describes an egg that has been fertilized by more than one sperm. Diploid organisms normally contain two copies of each chromosome, one from.