Meeting Abstract

19.5  Monday, Jan. 4  Buried Alive: The Physiological Ecology of Manduca sexta Pupal Chambers SPRAGUE, J. C.*; WOODS, H. A.; The University of Montana; The University of Montana jonathan1.sprague@umontana.edu

Many organisms mold the physical material of their environments to their own benefit, and these changes can have far reaching ecological and physiological effects (i.e., bird nests, beaver dams, ant colonies, and fossorial burrows). For instance, near Portal, Arizona, in the dry heat of the Chihuahuan and Sonoran Deserts, the sphingid moth Manduca sexta pupates for ~ 18 days, 3 to 11 cm below ground in carefully constructed chambers roughly twice the volume of their pupal case. These chambers are not cheap: larvae may spend over 6 hours wandering the desert floor to find suitable burrowing sites. They then spend several days and use up to 30% of their body mass in water weight to create and coat the chamber walls. But two benefits to pupating underground are immediately apparent. First, exposure to certain predators (wasps, ants, birds) is reduced. Second, while temperatures on the surface of the soil can reach 60°C (hot enough to fry an egg), a mere 6 cm down it’s a balmy and consistent 25-35°C. But why a costly, thick-walled chamber? Why not just dig down and pupate? We explore two possible functions of these chambers: (1) That the thick walls of the chamber retain water vapor and prevent desiccation in dry desert soil and (2) that chambers facilitate gas exchange to and from the pupa by creating a large soil-air interface.