Discontinuous gas exchange in insects: A clarification of hypotheses and approaches

Steven L. Chown, Allen G. Gibbs, Stefan K. Hetz, C. Jaco Klok, John R.B. Lighton, Elrike Marais

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137 Citations (Scopus)


Many adult and diapausing pupal insects exchange respiratory gases discontinuously in a three-phase discontinuous gas exchange cycle (DGC). We summarize the known biophysical characteristics of the DGC and describe current research on the role of convection and diffusion in the DGC, emphasizing control of respiratory water loss. We summarize the main theories for the evolutionary genesis (or, alternatively, nonadaptive genesis) of the DGC: reduction in respiratory water loss (the hygric hypothesis), optimizing gas exchange in hypoxic and hypercapnic environments (the chthonic hypothesis), the hybrid of these two (the chthonic-hygric hypothesis), reducing the toxic properties of oxygen (the oxidative damage hypothesis), the outcome of interactions between O2 and CO2 control set points (the emergent property hypothesis), and protection against parasitic invaders (the strolling arthropods hypothesis). We describe specific techniques that are being employed to measure respiratory water loss in the presence or absence of the DGC in an attempt to test the hygric hypothesis, such as the hyperoxic switch and H 2O/CO2 regression, and summarize specific areas of the field that are likely to be profitable directions for future research.

Original languageEnglish
Pages (from-to)333-343
Number of pages11
JournalPhysiological and Biochemical Zoology
Issue number2
Publication statusPublished - 1 Mar 2006
Externally publishedYes

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