Worker ants (30-42 mg body mass) were decapitated, the neck wound was sealed with wax and then subjected to flow-through respirometry using a LiCor CO2 analyzer and a Sable Systems FC-2 differential O2 analyzer. Traces for both gases showed the expected closed-flutter-open discontinuous gas exchange cycle. Respiratory exchange ratio (RER) across the entire cycle was 0.66 ± 0.04 (n=16), not significantly different from the predicted value of 0.73 (t=0.44, P=0.69). F-phase VCO2 was 1.2 µl/h and F-phase VO2 was 5.1 µl/h, resulting in an F-phase RER of 0.25 ± 0.03. The measured F-phase RER is consistent with that predicted for diffusion of oxygen and carbon dioxide along their transpiracular partial pressure gradients. These results demonstrate that, at least in ants, diffusion and not convection is the primary mechanism driving F-phase gas exchange and further support the hypothesis that the DGC evolved to facilitate gas exchange under hypoxic and hypercapnic conditions rather than as a means of restricting respiratory water losses.
Species 1: Hymenoptera Formicidae Camponotus vicinus
Keywords: gas-exchange, metabolic
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