Flexible nutrient oxidation during desiccation is associated with climate stress resistance of an invasive fly

The capacity of living organisms to withstand stress may be energetically expensive, thereby placing a demand on body nutrient stores and any nutrients that might be linked to coping with that stress. Here, we tested the hypothesis that desiccation-resistant Ceratitis capitata (Diptera: Tephritidae) and desiccation-sensitive Ceratitis rosa differentially oxidize nutrients to counter desiccation stress and facilitate recovery. Lines of flies from both species had their body macronutrient stores experimentally enriched with one of three 13C tracers: Leucine (enriches proteins), palmitic acid (enriches lipids), and glucose (enriches primarily carbohydrates), and were then subjected to a regimen of desiccation stress followed by recovery. We used flow-through respirometry and 13C-breath testing to detect changes in metabolic rates and macronutrient oxidation. Ceratitis capitata, unlike C. rosa, showed highly flexible metabolic rates and nutrient oxidation. The former upregulated oxidation of both carbohydrates and lipids whereas protein oxidation was only upregulated during recovery from desiccation. This provides novel support for biochemical pathway (macronutrient) flexibility enhancing the survival of a desiccation-resistant invasive species over a desiccation-sensitive species.