Parasitoid egg shell changes in a suitable and unsuitable host

Abstract

The egg shell of the braconid, Cardiochiles nigriceps , Viereck consists of two distinct layers: an inner, crystalline, proteinaceous chorion, and microvilluslike projections embedded in an outer fibrous chorion. In a suitable host the fibrous layer and projections are slowly lost during the first 12 hours. A new granular layer appears by 24 hours in place of the projections and fibrous layer. The structure of the fibrous outer layer of the egg shell is lost 2 hours after oviposition in an unsuitable host. The outer fibrous layer either changes to, or is replaced by, a microflocculate or coagulum by 6 hours. The projections persist through the first 12 hours but show signs of degeneration prior to encapsulation. The microflocculate increases in density until encapsulation by the hemocytes in about 24 hours. Hemocytes nearest the egg shell appear to show points of attachment. The possible role of the parasitoid egg and the host hemolymph is discussed with respect to immunity.