Premium
Oögenesis of the freshwater turbellarian Hydrolimax grisea (Platyhelminthes; Plagiostomidae) with special reference to the history of the supernumerary asters and central bodies
Author(s) -
Donald W. Donald
Publication year - 1970
Publication title -
journal of morphology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 74
eISSN - 1097-4687
pISSN - 0362-2525
DOI - 10.1002/jmor.1051320103
Subject(s) - biology , centriole , microbiology and biotechnology , nuclear membrane , anatomy , sperm , nucleus , botany
The oöcyte of H. grisea is surrounded early in its growth by the accessory cell. A yolk halo, secreted by accessory parenchymal cells, subsequently envelops the oöcyte and its accessory cell. Of particular interest are the supernumerary asters, and their central bodies, which surround the oöcyte nucleus. The asters are exceptional because they appear in unfertilized oöcytes with (apparently) intact germinal vesicle membranes. Coincident with sperm penetration the supernumerary asters grow. Their rays elongate and thicken. The nuclear membrane disappears. The supernumerary asters aggregate and disappear prior to the maturation (meiotic) divisions. The maturation asters from with distinct centrioles and centropheres while the egg is still within the parenchyma of the worm. Their formation is independent of sperm penetration. The polar bodies are given off within the cocoon.