Physiological and Biochemical Analysis of Factors in the Female Venom Gland and Larval Salivary Secretions of the Ectoparasitoid Wasp Eupelmus orientalis

Abstract

The stinging adult female and the biting newly-hatched larva of the solitary ectoparasitoid wasp Eupelmus orientalis can both cause permanent paralysis and stop the development of Callosobruchus maculatus host larvae. These two processes of host envenomation appeared to be independent and complementary in primary parasitism or in hyperparasitism of a distantly related hymenopteran host species. In contrast, the development of larvae as hyperparasites on members of their own species or genus depended completely on the prior injection of female venom. The venoms of the female and the first instar larva had similar effects on the cellular metabolism of the primary hosts. Protein synthesis was blocked in C. maculatus hosts envenomated by a female or a first instar larva of E. orientalis, but the absence of DNA breakdown indicated that these paralysed hosts were alive and quiescent. The venomous secretions injected by adult females and first instar larvae of E. orientalis had distinct electrophoretic profiles. The immunoreactive features of proteins from female venom and larval secretions were also examined. There is evidence for antigenic conservation between some venom proteins of E. orientalis and Apis mellifera. Lastly, the hyaluronidase, phospholipase and lipase activities in the female venom gland and in larval-derived secretions of E. orientalis were assayed. No lipase activity was detected. Phospholipase activity was found in both the female venom and the larval secretions of E. orientalis, whereas hyaluronidase was specific to the female venom.