Biology Reference
In-Depth Information
Fig. 23. Electron microscopic views of (A) egg showing micropyle and (B, D) entry of sperm
through the micropylar canal in an egg of Alcichthys alcicornis (from Munehara et al ., 1989).
Apical view of unfertilized eggs of (C) Gymnocorymbus ternetzi (lower) and Hemigrammus
caudovittatus (upper) and schematic views of their respective micropylar canals in eggs (from
David, 2004)
Ravaglia and Maggese (2002) have described the structure of micropyle
in eggs of the swamp eel Synbranchus marmoratus. The ovulated single
oocyte, drawn from the ovarian cavity, has a compact vitelline envelope
surrounding the oocyte with a single micropyle as the only entrance in
the animal pole (Fig. 24A). The vitelline envelope in the vegetative pole
has a polyhedrical surface that resembles 'fl oor tiles' (Fig. 24B). Over the
equatorial region, these tiles change their shape and elongate to form
isolated crests. Near the animal pole, these crests fuse together and become
Search WWH ::




Custom Search