SELECTION FOR LONGEVITY FAVORS STRINGENT METABOLIC CONTROL IN DROSOPHILA-MELANOGASTER

Models of the evolution of life span predict, and gerontological studi es show, a relation between nutrient use and life span. This study exa mines the role and comparative use of nutrients in long- and short-liv ed populations of D. melanogaster selectively bred for age-at-reproduc tion, without respect to metabolism or feeding rate. We test the hypot heses that selection for life span has favored the restriction of nutr ient use and that the observed effect of low population density during development is a consequence of modifying nutrient use. The use of nu trients was measured here by the uptake of radiolabeled glucose, its i ncorporation into lipid and protein, and by the in vivo metabolic flux through the pentose shunt. Measurements show that uptake, incorporati on, and flux are severely limited in long-lived stocks, compared to sh ort-lived populations of the same stage an stage of development. Raisi ng long-lived stocks at low population numbers relieves the restrictio n on metabolism in larvae, increasing incorporation and flux, and caus es adult life span to decline. Larvae of long-lived populations appear to feed less actively, suggesting that the reduction in use of nutrie nts could simply be from reduced intake. Changes in total soluble prot ein correspond with measurements of uptake, incorporation, and flux. S oluble protein is substantially less in long-lived stocks, before pupa tion, but catches up in early adulthood to that in the short-lived pop ulations. Despite different nutrient use by larval populations, only s light differences are found in development rate. They are insufficient to account for the differences observed in longevity.