Meeting Abstract

70.2  Monday, Jan. 6 08:15  Trade-offs amongst growth, storage and metabolic rate during the 5th instar of the tobacco hornworm, Manduca sexta HELM, BR*; DAVIDOWITZ, G; North Dakota State University, Fargo, ND; University of Arizona, Tucson, AZ bryan.r.helm@ndsu.edu

Juvenile organisms must invest incoming nutritional resources among growth, storage and maintenance, and tradeoffs among these traits will occur because incoming resources are limited. As a consequence, resources must be allocated so that survival and future reproduction are optimized both within a single growth trajectory and in light of environmental conditions experienced. In this study, we asked how the relationships among these traits change during ontogeny and in response to different environmental conditions. We examined growth rate, storage rate, and resting metabolic rate relative to increasing body size in last instar larvae of the tobacco hornworm, Manduca sexta. We measured these traits in individuals that had been reared at 30C, 25C, or 20C and on either a standard high quality or reduced low quality artificial diet. We found that the tradeoffs among these traits varied along ontogeny as the organism grew. During early growth of the last instar, growth rate, storage rate and metabolic rate were positively correlated. However, growth rate declined approximately half-way through the instar and became negatively correlated with increasing storage and metabolic rates. Environmental conditions affected growth, storage and metabolic rate, but the relationships among traits shared a common pattern across environmental conditions. We conclude that dynamic changes in the allocation scheme between these traits reflect evolved strategies for optimizing survival and future reproduction based on both developmental status and varying environmental conditions.