Alteration of egg architecture and egg activation in an endoparasitic Hymenopteran as a result of natural or imitated oviposition.

Ripe eggs of the Ichneumonid waspPimpla turionellae are activated by the deformation of the egg during oviposition or experimental treatment. The structure of eggs prior to oviposition differs from that of eggs after natural or imitated oviposition. Histologieal sections of preoviposition eggs show a conspicuous cytoplasmic reticulum, which is torn up in eggs after oviposition. The structure of total, living eggs which are treated mechanically, some of which subsequently develop, varies considerably. It is not possible to predict the developmental fate of an egg by its structural features. The observation of a variability in structure, also among normally developing eggs, supports our assumption that the function of the alteration of egg architecture lies in the triggering of processes rather than in the specific arrangement of an organization pattern. It is argued that at least 2 dynamic systems, one causing completion of meiosis and the other ooplasmic flows, must be activated in the egg by oviposition. We postulate, furthermore, that in the Hymenoptera egg, activation by deformation of the egg at oviposition is a common phenomenon.