METABOLIC ASPECTS OF THE TRADE-OFF BETWEEN FECUNDITY AND LONGEVITY INDROSOPHILA-MELANOGASTER

An antagonistic pleiotropy between early fecundity and longevity has b een well demonstrated in Drosophila melanogaster. It has been suggeste d that this pleiotropy may in part be due to a trade-off in energy all ocation between reproduction and survival. We have tested this hypothe sis by examining five populations of Drosophila melanogaster that show increased longevity following laboratory selection for postponed repr oduction. These were compared to five control populations. We measured body mass lipid and carbohydrate content, metabolic rate, and fecundi ty over the adult life span of the flies. Energy content brought forwa rd into the adult stage from the pupae and adult metabolic rate were i dentical for short- and long-lived flies. Long-lived flies showed decr eased fecundity and increased storage of lipid and carbohydrate compar ed to short-lived flies. Our study is the first to measure simultaneou sly allocations of metabolic energy resources between various forms of metabolic storage and reproduction in lines of Drosophila melanogaste r and to measure their equivalence using a common energy unit (J). Ene rgy equivalence analysis demonstrated that the trade-off in energy all ocation between fecundity and metabolic storage was not quantitatively , perfect with regard to energy values. Long-lived flies accumulated a dditional lipid and carbohydrate by forgoing early reproduction, buy t hese accumulated metabolic resources were far lower in energy content than were the additional eggs produced by short-lived flies.