Effects of dietary protein:carbohydrate balance on life-history traits in six laboratory strains ofDrosophila melanogaster

Drosophila melanogasterMeigen (Diptera: Drosophilidae) is a key model insect for studying life span and aging. Many laboratory strains ofD. melanogasterare currently used by laboratories worldwide, but they are known to vary considerably in their physiology, behavior, and life histories. Although the importance of dietary protein:carbohydrate (P:C) balance as a predominant determinant of life span and other life-history traits has been highlighted in recent research, it remains unexplored whether the impacts of P:C balance on these fitness-related traits vary in a strain-specific manner inD. melanogaster. In this study, we compared the life-history consequences (life span, egg production rate, pre-adult survival, development time, and body mass at eclosion) of six laboratory strains ofD. melanogaster(w1118,yw,Oregon-R,white Canton-S,Canton-S-SNU, andCanton-S-Inha) allocated to one of four synthetic diets differing in P:C ratio (1:16, 1:4, 1:1, or 4:1). The effects of dietary P:C balance on various adult and larval life-history traits were qualitatively similar across all strains studied in this study. Regardless of fly strain, adults exhibited a shortened life span and improved egg production on a diet with the highest P:C ratio of 4:1. In all strains, larvae raised on a diet comprising the lowest P:C ratio of 1:16 suffered high mortality, delayed development time, and reduced body mass. Despite the general similarity in the direction of the effect of P:C balance across strains, fly strains differed in the magnitude of their life-history responses to dietary P:C balance, as indicated by a significant interaction between fly strain and dietary P:C ratio for all measured traits except body mass at eclosion. Possible mechanisms explaining such strain-specific responses are discussed.