Lack of response to sex-peptide results in increased cost of mating in dunce Drosophila melanogaster females

Abstract

Drosophila melanogaster females homozygous for the dunce mutation have been reported to mate more often than females of a wild type stock (Canton-S). We have investigated the basis of this increased receptivity, by examining the response of dunce females, females of a revertant stock with the same genetic background and Canton-S females to injection with a component of the male accessory fluid (the ‘sex-peptide’, SP). dunce virgin females injected with SP showed no decline in receptivity towards courting males, whereas receptivity in control females was inhibited. dunce females also showed no inhibition of remating associated with the transfer of any non-sperm components at mating (the ‘copulation effect’) but did show a loss of receptivity due to the receipt of sperm (the ‘sperm effect’). The high remating rate of dunce females can therefore be attributed at least in part to their aberrant response to the receptivity-inhibiting SP. dunce females were no more susceptible than control females to the effects of a single mating; there was no significant difference in lifespan between dunce females mated once soon after eclosion and virgin dunce females. Twice-mated dunce females, however, had significantly shorter lifespans than virgin dunce females; this effect was not apparent in control dunce + revertant females. The high cost of mating incurred by dunce females is therefore due to a combination of their elevated remating rate and an increase in sensitivity to the effects of a fixed number of matings.