Feeding, fecundity and lifespan in female Drosophila melanogaster

Abstract

Male seminal fluid proteins induce a profound remodelling of behavioural, physiological and gene signalling pathways in females of many taxa, and typically cause elevated egg production and decreased sexual receptivity. In Drosophila melanogaster, these effects can be mediated by an ejaculate 'sex peptide' (SP), which, in addition, contributes significantly to the cost of mating in females. Recent research has revealed that SP can stimulate female post-copulatory feeding, raising the possibility that the widespread female cost of mating could be due to over-feeding. In this study, we used D. melanogaster as a model to test this hypothesis. We first show that elevated post-mating feeding is dependent upon egg production and does not occur in sterile ovoD1 mutant females. This conclusion was also supported by the increase in feeding of virgin females whose egg production was experimentally elevated. We then demonstrated that sterile ovoD1 and fertile females experienced identical survival costs of mating, related to their frequency of mating and not to female feeding rate or to egg production. We conclude that female mating costs are not the result of over-feeding, but may be due to other, potentially more direct, effects of ejaculate molecules.

Figure 1

Feeding rates (mean feeds per female±s.d.) of control and sterile ovo^D1 females mated to SP-transferring and SP-lacking males.

Figure 2

Feeding rates in virgin females with silenced fru neurons. Feeding rates (mean per vial per observation±s.e.) for experimental (UAS-shi^ts/+; fru^GAL4/+) and control (UAS-shi^ts/+ or fru^GAL4/+) virgin females at (a) restrictive (29°C) and (b) permissive (18°C) temperatures.

Figure 3

Survivorship against time in days for control and sterile ovo^D1 females exposed to high and low cost mating regimes (continuous versus intermittent exposure to mating males, respectively). (Black squares and triangles, high-cost sterile ovo^D1 and fertile females respectively; grey squares and triangles, low-cost sterile ovo^D1 and fertile females, respectively.)

Figure 4

Mean (±s.e.) egg laying rate against time in days for control females exposed to the fertile high-cost (black bars) and low-cost (grey bars) mating regimes as shown in figure 3.

Figure 5

Mean (±s.d.) female feeding rates/vial/observation/day for control and sterile ovo^D1 females exposed to the high- and low-cost mating regimes as shown in figure 3. Females exposed to either non-mating or wild-type males did not differ significantly in feeding rate (see text) and the data for all feeding assays were therefore combined.