OCCURRENCE AND FINE STRUCTURE OF SUBCORTICAL CYTOPLASMIC ISLETS IN FERTILIZED EGGS OF CYNOPS PYRRHOGASTER

Publisher Website
Google Scholar
Abstract
Fertilized and unfertilized eggs of C. pyrrhogaster were examined by light microscopy and EM. In fertilized eggs that were just laid there are numerous small cytoplasmic patches free of granules in the pigmented layer of the animal hemisphere. Many of these granule-free cytoplasmic islets, gradually grow out subcortically from the pigmented layer and fuse to form a subcortical layer of yolk-free cytoplasm of varying thickness by the time of the 1st cleavage division. The cytoplasmic islets are present in 100% of the fertilized eggs, but not in unfertilized eggs. EM observations showed that the cytoplasmic islets contain tubules and that development of a complex system of cortical tubules constitutes the basis of the early growth of the cytoplasmic islets. Cortical tubules are transient structures and are no longer observable a few hours after eggs are laid. These phenomena are apparently a response of the egg to the fertilization stimulus.