Synthesis and deposition of oocyte envelopes in the Colorado beetle, Leptinotarsa decemlineata Say.

Abstract

Electron microscopical and autoradiographic methods demonstrate that the secretion vesicles (SV), which are condensed by the Golgi-complexes of the follicle cells of the Colorado beetle, contain proteins which can be labelled with 3H-leucine. The labelled proteins are transported to the oocyte during vitellogenesis. At the end of yolk deposition, a few SV, situated just above the microvilli, disintegrate and give rise to the two layers of the vitelline membrane (VM). During the laying down of the VM or perhaps at a slightly earlier stage a layer is deposited beneath the basement membrane of the follicle cells. This layer may be important in inducing the formation of the egg membranes. Once the VM has formed, the follicle cells degenerate completely. The chorionic inner layer arises from the breakdown of SV, while the chorionic outer layer is formed from the degenerated follicle cells.