Ultrastructure and the relationship between the nucleolus and the nucleolar organizer region in Orthoptera male germ cells

Abstract

The ultrastructure of the nucleolus and the nucleolar organizer region, together with the relationships they maintain, are described in male germ cells of two species of grasshoppers. The nucleolus is multiple and appears related to a fibrillar center which seems to represent only a nontranscribing part of the organizer region. By means of serial sections, a particular relationship among the fibrillar center, the rDNA loops, and the nucleolar masses is suggested.Key words: ultrastructure, nucleolar organizers, nucleolus, Orthoptera.