Fine Structure of the Envelope and Micropyles in the Eggs of the White Sturgeon, Acipenser transmontanus Richardson. (micropyle/chorion/egg envelopes/sturgeon/egg jelly)

Publisher Website
Google Scholar
Abstract
The structure of the egg envelope and micropyles of the white sturgeon was examined with light and EM. The mature ovum is 3.5-4.0 mm in diameter and is covered by a thick envelope (50 .mu.m) that consists of 4 distinct layers. The outermost layer, L4, is electron-dense and amorphous. Interior to this is layer 3 (L3), containing numerous pores, or ductules. Layer two (L2) contains screwlike projections that anchor L3 and L4 to the egg. The innermost layer, L1, is closely apposed to the oolemma. Numerous micropyles (average 7) are restricted to a 100-200 .mu.m region at the animal pole and penetrate the egg envelope. The outer opening of these micropyles measures 15 .mu.m in diameter. The micropylar canal tapers twice, eventually terminating at the oolemma with an inner opening diameter of 1.2 .mu.m. The micropyles of the white sturgeon egg appear more complex than micropyles in other fish eggs.