Fatty acids are crucial primary metabolites for virtually any creature on earth. Therefore, most organisms do not rely exclusively on nutritional supply with fatty acids but have the ability to synthesize fatty acids and triacylglycerides de novo from carbohydrates, a process called lipogenesis. The ubiquity of lipogenesis has been questioned by a series of studies reporting that many parasitic wasps (parasitoids) do not accumulate lipid mass despite having unlimited access to sugar. This has been interpreted as an evolutionary metabolic trait loss in parasitoids. Here, we demonstrate de novo biosynthesis of fatty acids from ¹³C-labeled alpha-D-glucose in thirteen species of parasitoids from seven families. We furthermore show with the model organism Nasonia vitripennis that lipogenesis occurs even when lipid reserves are still intact, but relative ¹³C-incorporation rates increase in females with widely depleted fat reserves. Therefore, we conclude that the presumed ‘lack of lipogenesis’ in parasitoids needs to be re-evaluated.

The MS Excel data file contains the results of chemical analyses of lipid extracts from 13 parasitoid species by coupled gas chromatography-mass spectrometry. Data include peak areas of diagnostic ions from two fatty acid methyl esters to calculate relative incorporation rates. Extracted ion chromatograms of m/z 90 and m/z 87 were manually integrated at the retention times of palmitic acid methyl ester and stearic acid methyl ester. Resulting peak areas of m/z 90 were related to the summed peak areas of m/z 90 + m/z 87 and relative incorporation rates were calculated (%). Furthermore, peak areas (total ion current) of the six most abundant fatty acid methyl esters were related to an internal standard to calculate the fatty acid contents of lipid extracts and isolated triacylglyceride fractions. For more details see methods described at https://doi.org/10.1098/rspb.2021.0548.