Parasitism and the evolutionary loss of lipogenesis

Animals can adapt to fluctuating food conditions by accumulating energy reserves and so reduce unfavourable effects of low food supply on their growth and survival. However, within the Hymenoptera, several parasitoid species have been shown to be unable to store excess energy in lipid reserves. This proposal addresses the question why these species forego the possibility to accumulate lipid reserves as an adult and what the underlying mechanism is? We propose that the lack of lipogenesis in parasitoids is not confined to adults, but has resulted from selection for lack of lipogenesis in the larval stage. Lipogenesis is energetically very costly and parasitoid larvae could energetically benefit from lack of lipogenesis if they are able to obtain compensatory lipids from their host either directly or through manipulation of the host metabolism, which is not possible for herbivorous or carnivorous larvae. To test the idea that lack of lipogenesis is unique to parasitoids because of their parasitic larval life style and to understand how parasitoids avoid detrimental effects on basic cell processes the proposed research aims at answering three research questions: