Parasitic wasps have long been thought to be unable to synthesise fatty acids de novo, but recent ¹³C-labelling studies have challenged this view. It remained unclear, however, whether the reported biosynthesis rates are of biological relevance. Here, we show in Nasonia vitripennis that ageing females with partly depleted lipid reserves produce biologically relevant amounts of fatty acids de novo. Females with varying oviposition history (0-48 h) prior to feeding 20% ¹³C-labelled glucose solution showed ¹³C-incorporation rates of (mean ± SEM) 30±2%, 50±2%, 49±3%, and 21±2% in palmitic, stearic, oleic, and linoleic acid, respectively. The absolute amounts of fatty acids synthesised de novo across treatments corresponded to 28±3 egg lipid equivalents. Females incorporated de novo synthesised fatty acids into their eggs, and glucose-fed females laid more eggs than water-fed control females. The number of eggs laid prior to glucose feeding did not correlate with the degree of lipogenesis, but the amounts of de novo synthesised fatty acids correlated with constitutive (not synthesised de novo) fatty acids. Hence, glucose feeding has a twofold effect on the fatty acid status of N. vitripennis females by decelerating the catabolism of existing fat reserves and partially replenishing ebbing fat reserves by lipogenesis.

The MS Excel file contains six sheets entitled Figure 1 – Figure 6 referring to the figures of the original paper and the supplementary material, respectively.

The datasets in the tables "Figure 1-4" were obtained by the analysis of mass spectral data from ¹³C-labelling experiments. Wasps were fed solutions of fully ¹³C-labelled glucose of water (control) to investigate whether the sugar is incorporated into fatty acids thus indicating the de novo biosynthesis of fatty acids in the investigated species Nasonia vitripennis. Raw lipids of individual female wasps or eggs laid by the wasps were extracted with a solvent and extracted raw lipids were converted to fatty acid methyl esters (FAME). FAME were analysed by gas chromatography/mass spectrometry (GC/MS) and mass spectra of the four major FAME palmitic acid methyl ester (PAME), stearic acid methyl ester (SAME), oleic acid methyl ester (OAME), and linoleic acid methyl ester (LAME) were scrutinized for the occurrence of diagnostic ions indicative of the incorporation of ¹³C-carbon into the fatty acid chain. Extracted ion chromatograms of the diagnostic ions were integrated at the retention times of PAME, SAME, OAME, and LAME and peak areas of the labelled ions were related to the unlabeled analogues to determine ¹³C-incorporation rates. Additionally, individual amounts of FAME were determined by relating the peak areas of FAME in the total ion chromatograms to an internal standard (2-methyloctadecanoic acid methyl ester). The absolute amounts of de novo synthesized FAME were determined by applying ¹³C-incorporation rates to the determined masses of individual FAME.

The dataset in table "Figure 5" presents the results of an experiment studying the effect of glucose feeding on longevity and fertility of N. vitripennis females. Females were exposed for 16 days alternately (2-day periods) to a 20% unlabelled glucose solution and to host pupae for oviposition. Control females were provided with water instead. Parasitised hosts were removed after each oviposition phase and kept under rearing conditions until the offspring had emerged. Surviving females were counted daily and offspring produced by each wasp in each oviposition phase was counted.

The dataset in table "Figure S4" was obtained as described for "Figure 1-4". It containes ¹³C-incorporation rates for PAME and SAME obtained by two different calculation methods using the diagnostic ion pair m/z90 (labelled) and m/z87 (unlabelled) or the labelled molecular ion cluster (PAME: m/z 274, 276, 278, 280, 282, 284, and 286; SAME m/z 302, 304, 306, 308, 310, 312, 314, and 316) and the unlabelled analogues (PAME: m/z 270; SAME: m/z 298).

For more details see Materials and Methods of the original paper.