Figure 1. Lipid synthesis in adult parasitoids and other insects. Ingested sugars are converted to pyruvate through glycolysis, after which pyruvate is whether converted to acetate or used in the tricarboxylic acid (TCA) cycle to produce substrates for triglyceride (TAG) synthesis (citrate and glycerol-3-phosphate, i.e. G3P). Acetate andcitrate are converted to acetyl-CoA that enters the fatty acid synthesis pathway (left), and oxaloacetate is used to produce (G3P) that enters the glycerophosphate pathway (right). Triglycerides are also synthesized through the monoglyceride pathway. All three pathways are functional and active in insects in general. In contrast, parasitoids do not seem to synthesize triglycerides de novo through the glycerophosphate pathway, leading to the lack of triglyceride accumulation. Depicted metabolic pathways are simplified with enzymes highlighted in green, and reactions shown in red. Abbreviations: ACL, ATP-citrate lyase; ACS, Acetyl-coA synthetase; FAS, Fatty acid synthase; FACS, Fatty acyl-coA synthetase; GPAT, glycerophosphate acyltransferase; AGPAT, acylglycerophosphate acyltransferase; LPP, lipid phosphate phosphohydrolase;DGAT, diacylglycerol acyltransferase; MGAT, monoacylglycerol acyltransferase;MAG,mono(acyl)glycerides; DAG,di(acyl)glycerides; TAG,tri(acyl)glycerides; TCA cycle: tricarboxylic acid cycle.138139

From: Visser, B.,* Le Lann, C.,* Nieberding, C. M., Lammers, M., Hahn, D. A., Alborn, H. T., Enriquez, T., Scheifler, M., Harvey, J. A., & Ellers, J., Many parasitoids lack adult fat accumulation, despite fatty acid biosynthesis: considerations for future research. Accepted for publication in Current Research in Insect Science. Preprint available on EcoEvoRxiv - https://doi.org/10.32942/osf.io/zpf4j