Meeting Abstract

120.3  Saturday, Jan. 7  Do resource thresholds play a role in the onset of maturation--a key life history transition? HELM, BR*; DAVIDOWITZ, G; University of Arizona; University of Arizona bhelm@email.arizona.edu

Within the life history of a single organism, the onset of maturation marks a significant shift from the juvenile stage of life to the reproductive adult form. For a wide taxonomic sampling of organisms, this transition has been found to occur upon the attainment of a critical threshhold size near the end of larval growth after which hormonal and developmental mechanisms control maturation to the adult form. The internal physiological conditions that are assessed at the critical weight are, however, unresolved. An implicit assumption of life history theory is that the role of the juvenile stage acquire resources for growth and development. This pattern and theory lead to the hypothesis that the critical weight is triggered by the attainment of a resource threshold late in larval development. In this study, we use the model organism Manduca sexta to test two key predictions derived from this hypothesis: first, experimental augmentation of resources should move the critical weight forward in ontogeny, and 2.) environmentally-induced plasticity of the critical weight can be explained by differential rates of resource allocation to storage.