Meeting Abstract

P2.123  Monday, Jan. 5  The scaling of growth, nutrient assimilation and metabolism in larval hawkmoths raised on natural and artificial diets MINIUM, Sasha*; BASH, Ryan; SHANBHAG, Pratima; KERKHOFF, Andrew J.; ITAGAKI, Haruhiko; Kenyon College; Kenyon College; Kenyon College; Kenyon College; Kenyon College kerkhoffa@kenyon.edu

Recent theory attempts to explain metabolic scaling based on the evolutionary optimization of the structure and function of resource supply networks and exchange surfaces. However, we know of no studies that have simultaneously examined the scaling of both metabolism and resource exchange between animals and their environment. We use the larvae of tobacco hawkmoths (Manduca sexta), which grow ca. 10,000-fold in mass in 18 days, to investigate whether metabolic scaling is related to developmental changes in nitrogen (N) and carbon (C) assimilation and excretion. To examine the effects of diet quality (C:N), we also imposed a diet treatment, raising caterpillars on either a stock laboratory diet or on the leaves of tobacco (Nicotiana tobacum) a natural hostplant. Animals fed tobacco grew more slowly, and though they grew for a longer period, they reached a smaller asymptotic size. Tobacco fed animals also displayed metabolic scaling exponents shallower than those of animals fed the standard laboratory diet, which is consistent with other studies documenting the effect of food quality on metabolic scaling. The scaling of excretion (frass production) was similar to the scaling of metabolism, while the scaling of ingestion was shallower. Together, these results lead to a relatively simple model of ontogenetic growth and point to the potential importance of the stoichiometry (C:N balance) of nutrient uptake for understanding metabolic scaling and growth. This study is part of a larger NSF-funded undergraduate interdisciplinary research and training project (Manduca InSTaRs) assessing the role of midgut morphology and function in metabolic scaling.