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

摘要

This study aims at evaluating whether the bacterial endosymbionts of the pea aphid, Acyrthosiphon pisum, may be of any nutritional importance to the endophagous braconid parasitoid Aphidius ervi. Aposymbiotic aphids, obtained by rifampicin treatmenton artificial diet, were parasitized, and both parasitoid development and major changes in the nitrogen-derived nutrients in host haemolymph were observed. A. ervi larvae developing in aposymbiotic pea aphids showed a significant delay in reaching the adult stage, and the emerging adults showed a 50% weight reduction compared to those emerging from symbiotic aphids. In the haemolymph of parasitized symbiotic aphids, parasitism-specific proteins of approximately 15 and 45 kDa were detected, and their level increased on day 5 and 6 after parasitoid oviposition. At that stage, a significant increase in the free amino acid level was observed, with glutamine showing the highest relative abundance. In contrast, the haemolymph of aposymbiotic aphids did notcontain the two parasitism-specific proteins, and no increase in free amino acids was observed. The results indicated that the bacterial endosymbionts in parasitized pea aphids are of pivotal importance for the development of A. ervi. Aposymbiotic aphidshave a lower nutritional suitability, showing a significant reduction in the haemolymph of nitrogen-derived compounds of nutritional importance to the developing parasitoid larva. The possible role of Buchnera in nitrogen recycling is also discussed asa possible strategy for optimizing the utilization of dietary nitrogen by the parasitoid larva.