An analysis of resource allocation in response to dietary yeast in Drosophila melanogaster.

Drosophila melanogaster exhibit an increase in fecundity and a decrease in length of life and starvation resistance when the diet is enriched through the addition of live yeast. It has been proposed that this represents a necessary energetic trade-off between reproductive and somatic functions. We examined the metabolic aspects of this trade-off. We measured egg production, dry wt, somatic lipid and carbohydrate storage, and metabolic rate in response to changing amounts of live dietary yeast. These variables were measured in five replicate populations selected for postponed aging and five replicate short lived control populations. We find that all ten populations show an overall increase in egg production and decrease in the amount of stored metabolites in the presence of increasing amounts of yeast. All populations increase metabolic rate in response to increasing amounts of live dietary yeast. The energetics of this phenomenon suggest that increased egg production results from increased acquisition of nutrients available in yeast with only a small redirection of resources from storage to egg production.