Metabolic Aspects of the Trade-Off between Fecundity and Longevity in Drosophila melanogaster

An antagonistic pleiotropy between early fecundity and longevity has been well demonstrated in Drosophila melanogaster. It has been suggested that this pleiotropy may in part be due to a trade-off in energy allocation between reproduction and survival. We have tested this hypothesis by examining five populations of Drosophila melanogaster that show increased longevity following laboratory selection for postponed reproduction. These were compared to five control populations. We measured body mass, lipid and carbohydrate content, metabolic rate, and fecundity over the adult life span of the flies. Energy content brought forward into the adult stage from the pupae and adult metabolic rate were identicalfor short-and long-lived flies. Long-lived flies showed decreased fecundity and increased storage of lipid and carbohydrate compared to short-lived flies. Our study is the first to measure simultaneously allocations of metabolic energy resources between various forms of metabolic storage and reproduction in lines of Drosophila melanogaster and to measure their equivalence using a common energy unit (J). Energy equivalence analysis demonstrated that the trade-of in energy allocation between fecundity and metabolic storage was not quantitatively perfect with regard to energy values. Long-lived flies accumulated additional lipid and carbohydrate by forgoing early reproduction, but these accumulated metabolic resources were far lower in energy content than were the additional eggs produced by short-lived flies.