abstract: Studied is the establishment during oogenesis of the bilateral symmetry in the banana-shapedGryllus domesticus egg. Follicular length of the panoistic egg follicle is used for classification of oogenetic stages.External rotation symmetry of oocyte and follicle changes to the bilateral symmetric banana form at about 500μm of follicular length.Internal bilateral symmetry is already visible at this and younger stages with regard to the eccentric position of the oocyte nucleus. In the banana form of the oocyte the oocyte nucleus is located presumptive dorso-caudally. In the cylindric form it lies in the posterior half of the oocyte.The germinal vesicle itself exhibits a marked polarity: oocyte nucleolus and a crescent of granular material are always eccentrically located in the presumptive dorso-caudal quarter of the nucleus.Germinal vesicle's polarization and its slightly eccentric location become simultaneously visible in follicles 60 to 100μm of length. Thus at this time one can anticipate in a very early stage of oogenesis on the oocyte nucleus the future poles and axes of the coming embryo.Oocyte nucleus polarization and location appear to be uniform in all follicles of an ovariole and may presumably be due to external orientating factors.
authors.affiliation: Laboratorium für Elektronenmikroskopie des I. Zoologischen Instituts der Universität Göttingen, Deutschland.
authors.forename: Harald
authors.initials: H
authors.lastname: Netzel