VENTILATION AND RESPIRATORY METABOLISM IN THE THERMOPHILIC DESERT ANT, CATAGLYPHIS-BICOLOR (HYMENOPTERA, FORMICIDAE)

The discontinuous ventilation cycle of the Saharan desert ant Cataglyphis bicolor was studied over the range 15-40-degrees-C, corresponding to a > 2-fold increase in the rate of CO2 output and hence metabolic rate (Q10=2.1). Over this range, metabolic rate modulated only ventilation frequency; the volume of CO2 emitted per ventilation remained constant. The closed-spiracle phase accounted for a small, constant proportion (ca. 14%) of total CO2 output. In the flutter phase, the rate Of CO2 output increased at a greater than exponential rate from 29% of total CO2 output at 15-degrees-C to 52% at 40-degrees-C. CO2 output rate in the ventilation phase increased, and its duration decreased, exponentially with temperature. Relative to total duration of discontinuous ventilation cycle, the length of each phase was constant over the entire range of metabolic rates measured. These data are the first thorough characterization of the effect of changing metabolic rate on all phases of the discontinuous ventilation cycle of an adult insect. Clearly, C bicolor maximizes ventilation-phase emission volumes and enhances the contribution of the flutter phase to total CO2 release relative to other ants for which comparable data are available, and does so in ways that may reduce respiratory water loss rates.