Synthesis of fatty acids by the parasite Exeristes comstockii (Hymenop.) and two hosts, Galleria mellonella (Lep.) and Lucilia sericata (Dip.)

In contrast with many other insects, whose characteristic fatty acid compositions are influenced to a limited extent by dietary fatty acid composition, the fatty acid composition of the total lipid of the ichneumonid parasite Exeristes comstockii is very similar to that of its diet, that is, the host on which it is reared. When the parasite was reared on two hosts, Lucilia sericata and Galleria mellonella, with very different fatty acid patterns, it retained no characteristic fatty acid composition of its own.Radioisotope studies demonstrated that Exeristes comstockii, Galleria mellonella and Lucilia sericata incorporate 14C from 14C-1-acetate into fatty acids with radioactivity distributions consistent with de novo, elongation, and desaturation synthetic mechanisms.Exeristes comstockii was found to incorporate 14C-1-acetate into fatty acids at higher rates than either host. It appears, therefore, that the parasite has a fatty acid metabolism of its own, with respect to synthesis and turnover, although the fatty acids are qualitatively and quantitatively very similar to those in the host. The origin of the fatty acids of E. comstockii is partially explained by synthesis of fatty acids at different rates than its host, and direct incorporation of host fat, but the parasite appears to lack to great extent the control over pool size normally present in other insects.