Journals of Gerontology Series A: Biological Sciences and Medical Sciences, Vol 51, Issue 4 B284-B294, Copyright © 1996 by The Gerontological Society of America
Selection for longevity favors stringent metabolic control in Drosophila melanogaster
VF Riha and LS Luckinbill
Department of Biological Sciences, Wayne State University, Detroit, USA.
Models of the evolution of life span predict, and gerontological studies
show, a relation between nutrient use and life span. This study examines
the role and comparative use of nutrients in long- and short- lived
populations of D. melanogaster selectively bred for age-at- reproduction,
without respect to metabolism or feeding rate. We test the hypotheses that
selection for life span has favored the restriction of nutrient use and
that the observed effect of low population density during development is a
consequence of modifying nutrient use. The use of nutrients was measured
here by the uptake of radiolabeled glucose, its incorporation into lipid
and protein, and by the in vivo metabolic flux through the pentose shunt.
Measurements show that uptake, incorporation, and flux are severely limited
in long-lived stocks, compared to short-lived populations of the same stage
and stage of development. Raising long-lived stocks at low population
numbers relieves the restriction on metabolism in larvae, increasing
incorporation and flux, and causes adult life span to decline. Larvae of
long-lived populations appear to feed less actively, suggesting that the
reduction in use of nutrients could simply be from reduced intake. Changes
in total soluble protein correspond with measurements of uptake,
incorporation, and flux. Soluble protein is substantially less in
long-lived stocks, before pupation, but catches up in early adulthood to
that in the short-lived populations. Despite different nutrient use by
larval populations, only slight differences are found in development rate.
They are insufficient to account for the differences observed in longevity.
