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Abstract
Energy availability can limit the ability of organisms to survive under stressful
conditions. In Drosophila, laboratory experiments have revealed that energy storage
patterns differ between populations selected for desiccation and starvation. This
suggests that flies may use different sources of energy when exposed to these stresses,
but the actual substrates used have not been examined. We measured lipid, carbohydrate,
and protein content in 16 Drosophila species from arid and mesic habitats. In five
species, we measured the rate at which each substrate was metabolized under starvation
or desiccation stress. Rates of lipid and protein metabolism were similar during starvation
and desiccation, but carbohydrate metabolism was several-fold higher during desiccation.
Thus, total energy consumption was lower in starved flies than desiccated ones. Cactophilic
Drosophila did not have greater initial amounts of reserves than mesic species, but
may have lower metabolic rates that contribute to stress resistance.