Meeting Abstract

P2.153  Tuesday, Jan. 5  Modeling growth and metabolism in Manduca sexta larvae: variation across individuals and instars SEARS, K.E.*; MESSERMAN, A.F.; KERKHOFF, A.J.; ITAGAKI, H.; Kenyon College; Kenyon College; Kenyon College; Kenyon College kerkhoffa@kenyon.edu

Metabolism and material exchange with the environment are complex and intricately related processes that depend heavily on animal size. We developed a model of larval growth for the tobacco hornworm, Manduca sexta, an organism that grows 10,000-fold in approximately 18 days. Based on detailed daily measurements of food intake, frass production, carbon and nitrogen assimilation, animal mass, and metabolic rate, we document substantial physiological changes at or near times of molt. As a result, patterns of larval growth within each of their five instars may follow trends comparable to the ontogenetic trajectories of vertebrates. Models for growth integrating metabolic scaling and energy uptake that have been successfully applied to mammals and birds may thus be parameterized separately for each instar when applied to larval growth. Metabolic scaling exponents vary among instars and across individuals, and inter-individual variation may allow us to predict differences in growth among individual larvae. Our results suggest that relatively simple models relating metabolism and material exchange to growth in vertebrates can be extended to describe the complex ontogeny of insect larvae. At the same time, further studies of M. sexta will allow us to use controlled experiments to learn how variation in food quality, temperature, and living conditions influence the interactions between metabolic scaling, material exchange, and growth, while still considering a large range of magnitudes in animal size.