In vitro fertilization in ctenophores: sperm entry, mitosis, and the establishment of bilateral symmetry in Beroe ovata.

摘要: Abstract We have found ways to control in vitro fertilization a ctenophore (Beroe ovata) for the first time. This is based on existence of partial block self-fertilization at time gamete release which can be overcome by removal egg envelope. It has allowed us exploit excellent optical properties Beroe eggs make detailed observations all events from sperm penetration or penetrations these physiologically polyspermic cleavage, and extend our initial ( Carre Sardet, 1984 ). Sperm entry characterized local modifications cortex 70-μm zone around site sites. Upon entry, surface contracts relaxes locally, then cone forms disappears. These are accompanied localized exocytosis, growth ring microvilli, thickening cortex, gathering mitochondria pronuclei. The female pronucleus migrates beneath toward one successive fusion pronuclei, chromatin intermixing, mitosis were also observed with exceptional clarity. Furthermore, we noticed that direction last trajectory tends define orientation mitotic spindle, as consequence position unipolar cleavage furrow. turn determines future sagittal plane embryo adult B. ovata.