74.5 Friday, Jan. 6 Desiccation stress triggers a switch to exclusive carbohydrate catabolism in scorpions GEFEN, E*; KALRA, B; University of Haifa- Oranim, Israel email@example.com
The scorpion hepatopancreas serves as an essential storage compartment considering the often unpredicted availability of prey. During desiccating stress water is mobilized from the hepatopancreas to replenish hemolymph volume in order to retain its hydration and osmotic stability. Carbohydrate oxidation is advantageous under these conditions as it results in high metabolic water production rate per unit of ATP formed, as well as the release of glycogen bound water. We therefore hypothesized that scorpions switch to exclusive carbohydrates catabolism during desiccation stress. Laboratory acclimated scorpions were kept for 48h without feeding, and respiratory gas exchange rate ratios and hepatopancreas metabolic fuel content were determined following additional 0-5 weeks of desiccation at 30°C. Hepatopancreas water stores of the mesic Scorpio maurus fuscus (Scorpionidae) decreased significantly (p<0.05) following 1-week desiccation, consistent the species' high water loss rate. This response was delayed in the xeric subspecies S. m. palmatus. In contrast, the desiccation-resistant Buthotus judaicus and Leiurus quinquestriatus (Buthidae) maintained their initial fraction of hepatopancreas water for 4 weeks. Calculated RQ values indicate initial catabolism of a mixture of lipid, protein and carbohydrates (RQ~0.9) in all studied species. However, exposure to stressful conditions triggered a switch to exclusive carbohydrate catabolism (RQ not different from 1.0; α=0.05). The timing of this event correlated with the respective species' susceptibility to desiccation as manifested in depletion of their hepatopancreatic water stores. Determination of hepatopancreas metabolic fuel content reiterated the delayed switch to exclusive carbohydrate catabolism in the more resistant Buthidae.