P2.110A Thursday, Jan. 5 Developmental attenuation of high-fat diet-induced mortality in the tobacco hornworm caterpillar, Manduca sexta THAPA, Gita*; VERWORN, Natalie; GREENLEE, Kendra; North Dakota State University email@example.com
Availability of dietary protein may limit insect growth, and they respond to variable protein by altering behavior and physiology. Insects fed high carbohydrate diets have increased fat storage, and excess fat storage in insects may have a fitness cost. Do high lipid diets also result in adverse consequences in insects? Young Manduca sexta larvae reared on 5.6% fat diet had 80% mortality and 43% lower body mass compared to those reared on 3.4% fat or 0.4% fat diets. Older larvae showed no differences in mortality or body mass. Growth rates and development time differed slightly, as high fat fed caterpillars wandered later than those fed low and medium fat diets. To test the hypothesis that the increased survival of older larvae was due to increased lipid transport, we measured mRNA expression of Apolipoprotein I and II (APO1 and 2), proteins responsible for transporting lipids to the fat body and to various tissues. APO1 and 2 expression did not differ with dietary fat content. Interestingly, caterpillars fed a high fat diet during the first two days of the 5th instar ate less than others, possibly accounting for their slower development. When 5th instar larvae were given a choice between high fat and low fat diets, there was no difference in their preference. Preliminary analyses of fat body and fecal pellet lipid content showed no differences with diet, suggesting that the ability to digest and store the ingested lipid is similar among groups. To test the hypothesis that caterpillars are preferentially metabolizing fat during the 5th instar, we will measure the respiratory quotient of caterpillars on various diets. Although it is clear that 5th instar larvae are better able to tolerate dietary lipid, the mechanism remains unknown.