Living in a shallow burrow under a rock: Gas exchange and water loss in an Australian scorpion

The scorpion, Urodacus manicatus (Scorpionida: Urodacidae), inhabits temperate sclerophyll woodland in south-eastern Australia and excavates a shallow burrow into soil beneath a rock. Mean minimum and maximum temperatures within a burrow were respectively higher and lower than outside measurements, and relative humidity within a burrow remained higher than outside the burrow at all times. Using flow-through respirometry, VCO₂ and water loss were measured at three ecologically relevant temperatures (10, 20 and 30 °C) to assess patterns of gas exchange and the temperature dependence of VCO₂ and water loss rates. Daytime VCO₂ corresponds to a lower metabolic rate than reported for the closely related, but more arid region inhabiting species Urodacus armatus and Urodacus yaschenkoi. CO₂ output is continuous at 10 °C; however, at 20 °C scattered sharp depressions are observed and these become more frequent and periodic at 30 °C. Total water loss in U. manicatus is nearly double that in U. armatus, indicative of lessened selective pressure for water conservation within a mesic rather than xeric environment.