Meeting Abstract
31.4 Wednesday, Jan. 5 Interspecific Allometry of Cockroach Tracheal Systems and the Impact of Oxygen on Their Tracheal Development MUNOZ, E.E.*; WEED, M.; HARRISON, J.F.; VANDENBROOKS, J.M.; Arizona State University; Arizona State University; Arizona State University; Arizona State University elyse.munoz@asu.edu
The factors limiting insect body size are still poorly understood. One hypothesis is the possession of a tracheal system has led to oxygen-limitations on insect body size, with hyperoxia invoked to enable the evolution of insect gigantism in the past. In larger beetle species, the tracheal system occupies a larger proportion of the body, suggesting that trade- offs associated with increased tracheal investment or spatial limitations may set a limit on maximal size. Because tracheal investment also varies inversely with atmospheric oxygen, higher atmospheric oxygen levels might allow larger insect size with fewer costs. To test whether interspecific tracheal system hypermetry occurs in insects from primitive orders, we imaged the tracheal systems of cockroach species spanning three orders of magnitude (14 species from a 0.05-4.9g) using phase contrast x-ray synchrotron imaging at Argonne National Labs. Both the lateral abdominal and major leg tracheae exhibited tracheal hypermetry. This suggests that interspecific tracheal hypermetry may be a widespread insect phenomenon. To test whether atmospheric oxygen level would affect the tracheal system of cockroaches, as in several insects from more derived orders (fruit flies, beetles, caterpillars), we reared Blatella germanica under seven different oxygen levels ranging from 12-40%, and assessed their tracheal system morphology. Tracheal system investment was reduced in hyperoxia and increased in hypoxia. Thus, oxygen-modulation of tracheal investment occurs in insects from primitive orders, supporting the hypothesis that atmospheric oxygen level might have influenced tracheal morphology and body sizes of insects in the past. This research was funded by NSF EAR07463522.
