Water Relations of the Desert Scorpion, Hadrurus Arizonensis

Abstract

Total water-loss rates for Hadrurus arizonensis (0·028% wt/h at 30°C in dry air) are comparable to rates for Old World species and are well below rates for other desert arthropods under similar conditions. Cuticular and respiratory transpiration constitute the two major avenues of water loss, cuticular water loss predominating at temperatures up to approximately 38°C and respiratory transpiration predominating at temperatures above 40°C. The cuticular transpiration/temperature curve exhibits a two-plateau configuration with abrupt increases in cuticular permeability occurring between 35 and 40°C and between 65 and 70°C. Cuticular water-loss values in dead scorpions exceed those of total water loss in living scorpions. The increased cuticular permeability after death is interpreted as evidence for the existence of an active cuticular water-retaining mechanism. Water-loss rates are significantly reduced at lower saturation deficits; however, scorpions are unable to absorb significant quantities of water from near-saturated atmospheres or moist substrates, regardless of their hydration state. The importance of water conserving versus water regaining mechanisms are discussed in relation to the total adaptations of these animals to hot, dry environments.