Abstract
The endoparasitoid Glyptapanteles liparidis (Hymenoptera: Braconidae) injects polydnavirus and venom together with eggs into its Lymantria dispar (Lepidoptera: Lymantriidae) host larvae during oviposition. We studied effects of these parasitoid associated factors by means of g-irradiation-induced pseudoparasitization. The application of radiation for sterilization of female wasps as a tool to study interactions between parasitoid associated factors and the host is demonstrated in this paper. When wasps were irradiated at doses ranging from 24 to 96 Gy and then allowed to oviposit into L. dispar larvae, temporary sterilization was produced. On the first day post irradiation they laid 99% sterile eggs, but fertility recovered partially during the following days. Irradiation had no negative effect on the lifespan of wasps, but total fecundity was significantly reduced. Pseudoparasitization of L. dispar by irradiated G. liparidis caused prolonged larval development with supernumerary molts before pupation in females, and higher pupal weights in both sexes. Only 8 to 20% of pseudoparasitized larvae developed into adults; 20 to 33% died as larvae, 55 to 65% in pupae. Abnormities, such as precocious formation of pupal antennal pads in larvae or incomplete sclerotization of pupal cuticle occurred. Pseudoparasitization impaired the immune reactions of L. dispar larvae. Encapsulation of implanted plastic rods by hemocytes was reduced and hemolymph melanization was significantly suppressed 3 and 5 days post pseudoparasitization.
Highlights
The braconid wasp Glyptapanteles liparidis (Bouche) (Hymenoptera: Braconidae) is a gregarious endoparasitoid of Lymantria dispar (L.) (Lepidoptera: Lymantriidae) larvae
G. liparidis were obtained from our laboratory colony, originating from parasitized L. dispar collected in oak forests in Burgenland, Austria
All further reported data on the effects of pseudoparasitism stem from host larvae in which no developing parasitoids were found
Summary
The braconid wasp Glyptapanteles liparidis (Bouche) (Hymenoptera: Braconidae) is a gregarious endoparasitoid of Lymantria dispar (L.) (Lepidoptera: Lymantriidae) larvae. The wasp parasitizes young to mid-stage larvae; depending on host size at time of oviposition, females lay 5 to 50 eggs into the host’s hemocoel. After two to three weeks, the endoparasitic development is completed and larvae emerge from the host while molting to the third instar. They spin their cocoons for pupation next to the host larva which stays alive for a further few days, not capable of feeding and coordinated movements (Schopf, 1991; Schopf & Steinberger, 1996; Schopf & Hoch, 1997)
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