Oocyte growth, follicle cell differentiation and vitellin processing in the stick insect, Carausius morosus br. (Phasmatodea)

Ovarian growth in stick insects (Phasmatodea) was examined ultrastructurally and cytochemically with a view to studying: (1) the kinetics of oocyte growth and the staging characteristics of ovarian follicles undergoing vitellogenesis; (2) the endocytic capability of the growing oocyte, including the post-endocytic fate of the vitellins sequestered by the oocyte during vitellogenesis; (3) the differentiation of the follicular epithelium in relation to the appearance of intercellular spaces and the extracellular release of a follicle cell product. These structural observations were interpreted in relation to the nature and kinetics of the vitellin processing in follicles undergoing vitellogenesis.