Sex peptide receipt alters macronutrient utilization but not optimal yeast-sugar ratio in Drosophila melanogaster females

Abstract

Upon mating, females alter a multitude of physiological and morphological traits to accommodate the demands of reproduction. Changes not only include reproductive tissues but also non-reproductive tissues. For example, in Drosophila melanogaster the gut increases in circumference after mating, likely to facilitate a higher absorption and provision of macronutrients to maturing eggs. A male ejaculatory protein, the sex peptide, is instrumental to mediating several post-mating changes and receipt increases nutrient uptake as well as shifts taste preferences in mated females. We here tested whether sex peptide receipt also alters the protein: carbohydrate ratio at which females maximize their fitness. To test this, we mated females to males lacking sex peptide or control males and fed them with known volumes and concentrations of sugar and yeast. This enabled us to determine how the sugar to yeast ratio affects lifetime egg output as well as lifespan of females mated to the two male types. Sex peptide did not shift the optimal ratio. Instead, sex peptide receipt aided females in increasing their egg output at low macronutrient concentrations, but this advantage disappeared at higher macronutrient intake rates. Assuming that nutrient limitation might be common, then receipt of SP is beneficial under poor conditions.