Date of Award
Bachelor of Arts
Kerkhoff, Andrew J.
Metabolism, growth, and the assimilation of energy and materials are essential processes that are intricately related and depend heavily on animal size. Most models that attempt to explain the interactions between these processes have been applied only to mammals and birds and often rely on assumptions that have yet to be tested. Based on an insect-specific simplification of the West et al. (2001) ontogenetic growth model (OGM), we predict that the metabolic scaling exponent will have the same value as the scaling exponents of both growth and assimilation rates. We took detailed daily measurements of metabolic rate, animal mass, food ingestion, and frass production in larvae of the tobacco hornworm, Manduca sexta, an organism that grows 10,000-fold in only eighteen days. The scaling of growth rate generally followed the same pattern as that of metabolic rate, with similar scaling exponents both across and within instars. However, the rate of assimilation was much higher than expected early in larval development and did not match the patterns of scaling of growth and metabolism. Patterns of assimilation should be further explored to explain this deviation. Additionally, assimilation efficiency, which is usually assumed to remain constant throughout ontogeny, decreased substantially after the first molt period. Changes in assimilation efficiency combined with observed differences in the scaling of metabolism, growth, and assimilation between instars suggests that developmental stages are an important factor in scaling analyses, and larval insect development provides an ideal system for understanding the relationship between these three fundamental biological processes.
Sears, Katie, "Modeling metabolism, growth, and assimilation in Manduca sexta larvae: variation across individuals and instars" (2010). Honors Theses. 34.