Meeting Abstract

31.3  Wednesday, Jan. 5  Tracheal Growth and Plasticity in 5th Instar Manduca sexta HELM, BR*; DAVIDOWITZ, G; University of Arizona; University of Arizona bhelm@email.arizona.edu

In insects, oxygen is supplied directly to tissues through a network of branching trachea and tracheoles: tubules that branch inward from openings along the side of the body. The tracheal system is lined with the same hardened cuticle as the insect exoskeleton. Larval structures composed of cuticle grow when hardened cuticle is shed during molts. As such, it has long been assumed that tracheal growth can only occur during molts. However, some larval insects undergo ten-fold increases in size within a single larval instar, potentially stunting larval growth and development because of an inadequate oxygen supply. An unresolved question is how are these quickly growing larval insects able to adequately supply their tissues with oxygen, despite a tracheal system that presumably must be molted to grow larger? In this study, we demonstrate that tracheal systems grow an order of magnitude during the last larval instar in the tobacco hornworm, Manduca sexta, and that the tracheal mass relative to body size increases with reduced diet quality.