Ultrastructure of the female reproductive apparatus of the egg parasitoid Gryon pennsylvanicum (Ashmead) (Hymenoptera, Platygastridae)

•The general organization of the female genital apparatus of Gryon pennsylvanicum is studied.•The ultrastructure of the female reproductive apparatus is investigated by TEM.•The possible presence of virus-like particles in the oviduct of an egg parasitoid wasp is debated. The growing interest in Leptoglossus occidentalis, the conifer seed bug pest accidentally introduced into Europe in the 1990s, led us to investigate the female reproductive structures of the hymenopteran platygastrid Gryon pennsylvanicum, which is its candidate antagonist for biological control programmes. Our study revealed a genital apparatus with some characteristic features, such as an unusual length of the oviduct (divided into a long proximal and a short distal tract), the absence of accessory glands and the presence of a spermatheca provided with a small spermathecal gland. The ultrastructural investigation revealed that the shorter part of the common oviduct is involved in ion uptake whereas the longer part has two cell types with secretory function: the former with dense bodies and the latter with granular particles. The secretory contents of both are released into the oviduct lumen. The granular particles are formed in a complex of modified endoplasmic reticulum and appear as virus-like particles.