Developmental Changes in Fat Metabolism of Tobacco Hornworm, Manduca Sexta

Abstract

Insects fed high carbohydrate diets have increased fat storage, and excess fat storage in insects may have fitness costs. M. sexta larvae reared on 5.6% fat diet had lower body mass and growth rate compared to those on 3.4% fat or 0.4% fat diets. Fifth instar caterpillars fed high-fat diet ate less food but had higher approximate digestibility than the low-fat diet fed caterpillars. Analysis of fat body and fecal pellet lipid content showed high-fat diet fed caterpillars stored and excreted more lipids than low-fat diet fed caterpillars. To test the hypothesis that increased dietary fat alters lipid transport, we measured mRNA expression of apolipoproteins I and II, proteins for transporting lipids. Expression of apolipoproteins I and II did not differ with dietary fat. Negative feedback from fat intake could inhibit feeding via endocrine pathways. This research will increase our understanding of the regulation of feeding in caterpillars.