Meeting Abstract

65.3  Jan. 7  Gas exchange patterns in beetles from Southwestern USA KAISER, A.*; QUINLAN, M. C.; Midwestern University, Glendale, AZ; Midwestern University, Glendale, AZ akaise@midwestern.edu

The unique CO₂ release pattern of discontinuous gas exchange (DGE) in insects is often assumed to have evolved to conserve body water. Recently, several alternative hypotheses have been presented to explain the adaptive significance of the gas exchange pattern (reviewed in Chown et al. 2006, Physiol. Biochem. Zool. 79, 333-343). Testing these hypotheses has proven difficult and far too few species have been investigated to obtain agreement about which hypothesis is correct. We address this issue by examining three families of beetles in the Southwestern US, occupying a wide range of habitats. So far, we have examined a total of 50 species: 22 Scarabaeidae, 18 Tenebrionidae and 10 Carabidae. We detected three patterns of gas exchange (DGE, cyclic, and continuous). We classified the respiratory patterns in every beetle and correlated them with phylogeny, habitat, wing status and “cryptic” lifestyle, where beetles are – at least occasionally – hidden under dung, soil, rocks, bark or in burrows. Most of the Carabidae and Scarabaeidae exhibited cyclic or discontinuous gas exchange (Carabidae: 20.0% DGE, 70.0% cyclic; Scarabaeidae: 18.2% DGE, 72.7% cyclic). Tenebrionidae were more likely to show continuous gas exchange (55.6%). There was no association between xeric habitat and the occurrence of cyclic gas exchange or DGE. The occurrence of DGE was weakly correlated with a cryptic life style. We found strong associations between the occurrence of DGE or cyclic CO₂ release and the possession of wings. The adaptations of winged beetles to high metabolic demands during flight might be associated with the evolution of discontinuous gas exchange patterns during resting periods. Supported by NSF grant IBN�0344963 to M.C.Q.