Development and nutrition of the braconid wasp, Aphidius ervi in aposymbiotic host aphids

This study aims at evaluating whether the bacterial endosymbionts of the pe a aphid, Acyrthosiphon pisum (Harris), may be of any nutritional importance to the endophagous braconid parasitoid Aphidius ervi Haliday, Aposymbiotic aphids, obtained by rifampicin treatment on artificial diet, were parasiti zed, and both parasitoid development and major changes in the nitrogen-deri ved nutrients in the host hemolymph were observed. A. ervi larvae developin g in aposymbiotic pea aphids showed a significant delay in reaching the adu lt stage and the emerging adults showed a 50% weight reduction compared to those emerging from symbiotic aphids, In the hemolymph of parasitized symbi otic aphids, parasitism-specific proteins of approximately 15 and 45 kD wer e detected, and their level increased on day 5 and 6 after parasitoid ovipo sition. At that stage, a significant increase in the free amino acid level was observed, with glutamine showing the highest relative abundance. In con trast, the hemolymph of aposymbiotic aphids did not contain the two parasit ism-specific proteins and no increase in free amino acids was observed. The results indicate that the bacterial endosymbionts in parasitized pea ap hids are of pivotal importance for the development of A. ervi, Aposymbiotic aphids have a lower nutritional suitability, showing a significant reducti on in the hemolymph of nitrogen-derived compounds of nutritional importance to the developing parasitoid larva, The possible role of Buchnera in nitro gen recycling is also discussed as a possible strategy for optimizing the u tilization of dietary nitrogen by the parasitoid larva, Arch. Insect Bioche m, Physiol, 40:53-63, 1999. (C) 1999 Wiley-Liss, Inc.