We measured CO2 and H2O release from individual fruit flies from five populations of Drosophila melanogaster selected for resistance to desiccation (D flies). Our previous work found that these flies survive for an extended period in dry air, have an increase in the peak height and frequency of CO2 release, as measured by the standard error of a linear regression (SER) of CO2 release for the entire survival period, and have reduced water loss rates (VH2O) compared with their control or ancestor populations. In the present study, we examined the following respiratory characteristics: VCO2, VH2O, the SER of CO2 release and the ratio of VCO2 to VH2O in the D flies. Correlations between these characters were calculated in order to determine the effect of respiratory pattern on water loss. We found that, within the D flies, neither periodic release of CO2 nor an increased SER for CO2 release was associated with reduced water loss. In addition, an increased SER was positively correlated with both an increased water loss rate and a decreased survival time. Therefore, although selection for desiccation resistance leads to both an increased SER and a decreased rate of water loss in the D flies, the increased SER does not significantly reduce respiratory water loss.

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