Effects of parasitoid associated factors of the endoparasitoid Glyptapanteles liparidis (Hymenoptera: Braconidae)

Abstract

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 γ-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.

Gamma radiation-induced pseudoparasitization as a tool to study interactions between host insects and parasitoids in the systemLymantria dispar(Lep., Lymantriidae)–Glyptapanteles liparidis(Hym., Braconidae)

“…PDV/venom prevented the fatal immune response. Previous work had already shown that pseudoparasitized L. dispar larvae show reduced encapsulation of implanted artificial objects and reduced hemolymph melanization (Tillinger et al 2004). However, as is suggested by our findings from the dissections, G. liparidis larvae implanted without teratocytes still suffered some attack from the host immune system and were apparently unable to complete their development.…”

“…Glyptapanteles liparidis females were g-irradiated based on the method outlined in Tillinger et al (2004). Six-day-old female wasps with at least one oviposition experience were placed in ventilated 10 )10 )15-cm plastic boxes and irradiated with 96 Gy (at a dose rate of 25.6 Gy/min) in a Gammacell 220 cobalt-60 irradiator (Atomic Energy of Canada Ltd.) at the FAO/IAEA Agriculture and Biotechnology Laboratories, Seibersdorf, Austria.…”

“…We explored a method to study the effect of PDV plus venom in the system G. liparidisÁL. dispar by sterilizing female wasps with g-radiation from a cobalt-60 source (Tillinger, Hoch, and Schopf 2004). Such irradiation is normally used in sterile insect (SIT) programs (Bakri, Mehta, and Lance 2005;Klassen and Curtis 2005).…”

“…A disadvantage is that PDV and venom can only be studied together. Radiation-induced pseudoparasitization by G. liparidis was shown to affect both, host development Á resulting in prolonged development and frequently incomplete metamorphosis Á and immune competence (Tillinger et al 2004).…”

Cloning, characterization and analysis by RNA interference of various genes of the Chelonus inanitus polydnavirus

“…Non-parasitized and X-ray-parasitized larvae pass through six larval instars, but the latter become developmentally arrested in the prepupal stage, as do larvae developing from eggs injected with CiV/ venom (Soller & Lanzrein, 1996). X-ray irradiation of wasps (24-96 Gy) has recently also been used in another parasitoid-host system to study the role of the associated bracovirus (Tillinger et al, 2004).…”