Quarterly Journal of Microscopical Science, Vol s3-102, 119-129, Copyright © 1961 by Company of Biologists

A Morphological and Histochemical Study of Oogenesis in the Gall-fly Cynips folii

M. KRAISKA ¹

¹ Histology and Embryology Department, High School of Agriculture, Warsaw; M. Nencki Institute of Experimental Biology, Warsaw, Poland

In the ovariole of Cynips, cell groups that have arisen in the initial period of oogenesis, presumably from one gonial cell, differentiate into the oocyte and 12 nurse cells (which constitute the nutritive chamber). The oocyte remains connected with the nurse cells by a strand of cytoplasm; the whole group acts as a physiological unit till the completion of vitellogenesis. Ribonucleoproteins are synthesized in the nurse cells and transmitted to the oocyte. The latter produces no detectable RNA.

There is no morphological evidence of any interchange of material between the nuclei or nucleoli and the cytoplasm of the oocyte or nurse cells.

Protein yolk components appear in the oocyte around the RNA inflow from the nurse cells. They associate with mucopolysaccharides, which appear in the same territory, to form carbohydrate-protein complexes. The synthesis of lipid yolk starts in the posterior part of the undifferentiated cell group and occurs subsequently only in the oocyte.

Nurse cells never penetrate inside the oocyte in normal undamaged ovarioles. They shrink and disintegrate outside the ovariole after completion of their life-cycle.

The anterior part of the oocyte develops into the egg pedicel with a terminal extension in which most of the glycogen of the cell is accumulated; the protein spheres in this extension are different from the protein yolk of the main part of the oocyte. The precursors of these protein spheres arise in the cytoplasm of the common cell group before the onset of yolk formation.

The function of the follicular epithelium is secretion of the egg envelope, which is of epicuticular nature. The penetration of material from the haemolymph to the oocyte occurs mainly through the cells of the nutritive chamber. The contribution of the follicular epithelium to this process seems to be of minor importance, at any rate in the early stages.