Discontinuous gas exchange in the fire ant, Solenopsos invicta Buren:: Caste differences and temperature effects

The discontinuous gas exchange cycle (DGC), the cyclic release of CO2 and uptake of O2, were investigated in workers and female and male alates of the red imported fire ant, Solenopsis invicta Buren, using real-time CO2 emission measurement by flow-through respirometry. All S. invicta castes displayed discontinuous emission of CO2 in the temperature range of 15–25°C, but only male alates and workers exhibited a DGC at 30°C. The closed (C) and flutter (F) periods of the DGC were distinguishable in alates of both sexes at the lowest temperature, but not clearly differentiated in females at temperatures above 15°C, in males above 20°C, or workers at any temperature. DGC frequency increased for all castes as temperature increased, ranging from a low of 0.9±0.05 mHz (male alates at 15°C) to 18±0.79 mHz (workers at 30°C). O period (or burst) volumes of all castes decreased as temperature increased, and increased with body mass — this mass effect was most pronounced at lower temperatures. Q10 values for DGC frequency (4.27, 5.81, and 5.62 for workers, female and male alates, respectively) were high compared with Q10ʹs for standard V̇CO2. Differences in the salient characteristics of the DGC between castes are presented and discussed, and S. invicta DGC patterns are compared to known values for some other ant species.