Meeting Abstract

P1.115  Monday, Jan. 4  Respiratory water loss and the effects of activity on the water budget in scorpions GEFEN, E.; Univ. of Haifa- Oranim, Israel gefene@research.haifa.ac.il

The geographic distribution of Buthotus judaicus (Buthidae) and Scorpio maurus fuscus (Scorpionidae) in Israel is limited to the mesic Mediterranean zone. Nevertheless, the two sympatric species have been shown to vary greatly in their water relations traits. When exposed to prolonged desiccation B. judaicus maintains its hydration state and hemolymph osmolarity better than S. m. fuscus. In order to determine the relative importance of respiratory water loss (RWL) to their water budget, metabolic rates (MR, measured as CO₂ output) and water loss rates (WLR) of hydrated scorpions were measured at 30°C. No significant differences were found between resting MR of B. judaicus and S. m. fuscus (F_1,23=3.57; p=0.07), or their H₂O to CO₂ output ratio (p=0.49). The relative importance of RWL at rest (16.8±1.5 and 15.1±1.8%, respectively) did not differ significantly (p=0.72), indicating that variation in cuticular permeability is largely responsible for the ~40% lower resting WLR of B. judaicus (F_1,23=25.8; p<0.001). However, continuous respirometry for 24h revealed marked differences in activity patterns between the two species. Mean daily MR of S. m. fuscus were 2-fold higher than those measured for B. judaicus. Elevated RWL resulting from activity represent a 20.7% increase from mean total water losses of resting S. m. fuscus (7.8% in B. judaicus). The relatively high fraction of RWL associated with activity, and previously reported decreasing WLR of S. m. fuscus during prolonged desiccation, suggest that some scorpions may downregulate their activity in order to conserve body water under stressful conditions.