Meeting Abstract

70.1  Monday, Jan. 6 08:00  Nutrient effects on energy allocation among body parts within an individual. DAVIDOWITZ, G.*; DAWS, A.D.; MOORE, A.F.; HELM, B.R.; STILLWELL, R.C.; University of Arizona; University of Arizona; University of Arizona; North Dakota State Univ., Fargo; Univ. of Lausanne, Switzerland goggy@email.arizona.edu

We use a common currency, calories, to examine relative investment among body parts (head, thorax, legs, wings, abdomen) within individuals as a function of body size, diet quality, and sex, in the hawkmoth Manduca sexta. 50-90 moths per sex, per diet (478 total), were disarticulated and each body part dry weighed. Separate calibration curves for the caloric content of each body part, diet, and sex were generated using a bomb calorimeter. These calibration curves were used to calculate the predicted caloric content of each of the 5 body parts in the 478 moths. As expected, moths invested more into individual body parts as diet quality increased. Contrary to our prediction, however, males and females allocated resources very differently when diet quality varied. For example, mass-specific (cal/g) allocation to the thorax in females increased with thorax size on high quality diet but decreased on low quality diets. This trend was opposite in males: as thoraces increased in size, cal/g decreased on high quality diet but increased on low. To our surprise, tradeoffs in caloric investment were seen only between the abdomen and other parts. The head, thorax, wings and legs did not trade off with each other in caloric content. These patterns of tradeoffs held for both sexes and all diets. Together these results show that males and females have different rules of mass-specific caloric investment into individual body parts when diet quality varies. These results help explain differences in flight performance between males and females, but further implications of these different allocation rules require further study.