Table 1.

Water loss rate and cuticular permeability

SpeciesDrosophila melanogasterForelius mccookiPogonomyrmex californicusPogonomyrmex californicus
Temperature (°C)20204020
Individuals measurement-14–111011
N 9676
Individual mass (μg)1000±20270±206760±5307660±180
CO2 (μl hr-1 insect-1)1.98±0.140.26±0.018.98±0.601.69±0.25
MR (μW)11.52±0.831.52±0.0869.60±4.6313.09±1.90
SMR (μW)1.86±0.100.61±0.0438.14±2.5810.63±0.22
Total WLR (μg hr-1 insect-1)45.57±3.2115.33±1.15547.05±78.86106.62±12.42
Area-specific WLR (μg hr-1 cm-2)449.86±38.23358.53±29.991461.14±156.71265.46±29.79
Uncorrected CP (μg hr-1 cm-2 Torr-1)25.84±2.1920.57±1.7026.51±2.8415.25±1.71
Corrected CP (μg hr-1 cm-2 Torr-1)19.74±1.33*18.31±1.68*25.22±2.9614.39±1.61
Reduction CO2 (%)46.12±4.0871.77±2.5588.35±5.56NA
Reduction WLR (%)9.43±1.13*5.34±1.18*4.79±1.24NA
Respiratory WLR (%)22.86±3.59*7.59±2.01*5.58±1.475.64±0.49
Peak CO2 (%)109.73±8.65208.61±8.60327.66±36.07NA
Peak WLR (%)185.23±33.77149.90±22.2469.62±13.38NA
Plateau WLR (%)18.48±13.6130.67±6.2643.52±8.48NA
  • Values are mean ± s.e. WLR, water loss rate. CP, cuticular permeability, either raw (cuticular + respiratory) or corrected by subtraction of respiratory water loss (see text). Peaks or reductions in CO2 or H2O are expressed as percent above or below the normoxic steady-state condition, respectively. Respiratory WLR is expressed as percent of total WLR. WLR plateau after N2 is expressed as percent over the normoxic steady-state condition. SMR is standard metabolic rate predicted by the allometric equation for inactive tracheate arthropods (Lighton et al., 2001). NA, not applicable. *One value missing. See text, especially for RWL comparisons in P. californicus between 20°C (discontinuous gas exchange) and 40°C (continuous gas exchange). Torr≡133.3 Pa.