Synthesis of the vitelline and chorionic membranes of an ichneumonid parasitoid

A reduction in free ribosomes and increases in rough endoplasmic reticulum and Golgi complexes in follicle cells during oogenesis suggest their involvement in supplying precursor material for synthesis of the vitelline and chorionic membranes of the ichneumonid parasitoid Campoletis sonorensis. The inner region of the vitelline membrane is composed of a narrow band of electron-opaque material; an outer region adjacent to the chorion consists of overlapping, irregularly shaped laminae. The fully developed chorion can be divided morphologically into three distinct regions. Its inner region adjacent to the lamellar plates of the vitelline membrane is composed of a lamellar membrane exhibiting a regular periodicity of crossbands. The middle section is composed of longitudinal chambers, some of which contain particulate matter. The outer region consists of slender projections which extend perpendicularly from the chorion surface. A fine layer of fibrous material adheres to the projections. The possibility of a relationship between the presence of fibrous material on the surface of parasitoid eggs and the inactivation or inhibition of host immune systems is mentioned.