Effect of mating status on Drosophila virilis lifespan.

Mating status markedly affected the lifespan of Drosophila virilis flies but the effects of virginity on lifespan were different between the sexes. In all cases lengthening of female lifespan and shortening of male lifespan were observed as an effect of virginity. Lifespan was also affected either by the population density or by the sex ratio per culture. At a sex ratio (proportion of females) of 0.5, lifespan was constant in both sexes irrespective of the population density and females lived significantly longer than males. At high (0.9) and low (0.1) sex ratios mean lifespan did not differ between sexes, but it was longer at high sex ratios than at low ones. A negative correlation between mean lifespan and the number of males per vial was revealed for both sexes. Effects of mating on egg-laying activity were also analyzed. Although the number of eggs laid during the first 20 days period after eclosion was greater in mated females than in unmated virgin females, lifetime egg production was not always larger in the former than in the latter. No particular relationship between egg-laying activity and female lifespan was proven. The lifespan of D. virillis flies seemed to be determined by complex interactions between both sexes, in which the sexual activity of males may play the most important role.