Influence of parasitism on metabolites of the light brown apple moth, Epiphyas postvittana

Parasitism modifies the balance between storage and availability of key nutrients in parasitized hosts.  These modifications can be influenced by many factors including the parasitoid’s feeding strategy, ectoparasitism versus endoparasitism, and the developmental stage of the host and parasitoid. Three major metabolites that are modified in the hemolymph and fat body and effect the successful development of the parasitoid are proteins, carbohydrates and lipids. Metabolite concentrations were measured for larvae of Light Brown Apple Moth, Epiphyas postvittana (Lepidoptera: Tortricidae) following parasitism by either a braconid endoparasitoid, Meteorus ictericus, or a bethylid ectoparasitoid, Goniozus jacintae. We estimated metabolite concentrations in 5^th instar host larvae for parasitoid developmental stages represented by 1, 4, and 7 days after oviposition at 26°C.  In the hemolymph, the concentration of proteins decreased and the carbohydrates increased with time following parasitism. Lipids decreased in the host’s fat body and increased in the hemolymph in the later stages of the ectoparasitoid development.  In contrast, lipid concentration in both the host’s fat body and hemolymph did not change significantly when parasitized by the endoparasitoid or in the control host. Preliminary SDS PAGE results also indicate the expression of at least two parasitism-specific proteins in the hosts parasitized by the ectoparasitoid at day 4 and day 7 of development. These results demonstrate that significant modifications of major metabolites are apparent in the host’s hemolymph and the fat body over the course of a parasitoid’s development and that the rates differ with parasitoid feeding strategy and stage of development.