Meeting Abstract
Most of our understanding about the physiology of fasting and starvation comes from studies of vertebrates; however, studies that monitor vertebrates through the lethal endpoint are scant. Insects are convenient models to characterize the comparative strategies to cope with starvation because they have diverse life histories and have evolved under the omnipresent challenge of food limitation. Moreover, we can study the physiology of starvation through its natural endpoint. In this study we raised populations of five species of insects (adult grasshoppers, crickets, cockroaches, and larval beetles and moths) on diets labeled with 13C-palmitic acid or 13C-leucine to isotopically enrich the lipids or the proteins in their bodies, respectively. The insects were allowed to become postabsorptive and then starved. We periodically measured the δ13C of the exhaled breath to characterize how each species adjusted their relative reliance on endogenous lipids and proteins as energy sources. We found that starving insects employ a wide range of strategies for regulating lipid and protein oxidation. All of the insects except for the beetle larvae were capable of sharply reducing reliance on protein oxidation; however, this protein sparing strategy was not always sustainable during the entire starvation period. At death, the crickets and cockroaches were relying extensively on protein oxidation but the other species were not. All insects increased their reliance on lipid oxidation, but while some species (grasshoppers, cockroaches, and beetle larvae) were still relying extensively on lipids at death, other species (crickets and moth larvae) allowed rates of lipid oxidation to return to prefasting levels. We conclude that starving insects exhibit a much wider range of strategies for rationing lipids and proteins than vertebrates.
