LACK OF RESPONSE TO SEX-PEPTIDE RESULTS IN INCREASED COST OF MATING IN DUNCE DROSOPHILA-MELANOGASTER FEMALES

Drosophila melanogaster females homozygous for the dunce mutation have been reported to mate more often than females of a wild type stock (C anton-S), We have investigated the basis of this increased receptivity , by examining the response of dunce females, females of a revertant s tock with the same genetic background and Canton-S females to injectio n with a component of the male accessory fluid (the 'sex-peptide', SP) , dunce virgin females injected with SP showed no decline in receptivi ty towards courting males, whereas receptivity in control females was inhibited, dunce females also showed no inhibition of remating associa ted with the transfer of any non-sperm components at mating (the 'copu lation 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 respon se to the receptivity-inhibiting SP, dunce females were no more suscep tible than control females to the effects of a single mating; there wa s no significant difference in lifespan between dunce females mated on ce soon after eclosion and virgin dunce females. Twice-mated dunce fem ales, however, had significantly shorter lifespans than virgin dunce f emales; this effect was not apparent in control dunce revertant female s, The high cost of mating incurred by dunce females is therefore due to a combination of their elevated remating rate and an increase in se nsitivity to the effects of a fixed number of matings. Copyright (C) 1 996 Elsevier Science Ltd