Structure of the trophic chamber and follicular epithelium in ovaries of the model heteropteran species Pyrrhocoris apterus.

The studies concern organization of the female gonads and the course of oogenesis in the model species of Heteroptera, Pyrrhocoris apterus. Morphological, cytochemical and ultrastructural analyses were carried out. Each of the paired ovaries of the studied bug comprises seven telotrophic ovarioles. An individual ovariole is composed of the terminal filament, tropharium, vitellarium, and ovariole pedicle. The tropharium houses morphologically diversified trophocytes. In the apical part small individual nurse cells are located, some of them are mitotically active. Below this zone nuclei of the trophocytes divide amitotically. The main part of the trophic chamber is composed of cytoplasmic lobes containing several trophocyte nuclei. Each lobe connects with the trophic core by cytoplasmic extension. In the basal part of the tropharium early previtellogenic oocytes and somatic prefollicular cells occur. The vitellarium houses oocytes at different developmental stages, surrounded by follicular cells, with younger oocytes positioned apically and older ones basally. The contact between oocytes and trophocytes is maintained by nutritive cords filled with densely packed microtubules. Numerous ribosomes and mitochondria occur within the cords. The follicular epithelium undergoes a series of changes and diversifies into three subpopulations. The general organization of P. apterus ovarioles is similar to that described in other representatives of Heteroptera. The differences concern the structure of the tropharium, the number and growth rate of ovarian follicles and the course of differentiation of the follicular epithelium.