Costs of reproduction in female Drosophila melanogaster

• Main Author: Chapman, Tracey
• Published: University of Edinburgh 1993
• Subjects: 591.35
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.642746

The experiments presented in this thesis investigated the mechanisms of costs of reproduction in female <i>Drosophila melanogaster</i>. There was no evidence to support the existence of seminal feeding, as remating was not more beneficial for females when they were nutritionally stressed. Continual exposure to males did not lead to an increase in female reproductivy success, suggesting that females were not maximising their reproductive output by frequent rematings. Females that remated often suffered a cost of mating, as a decrease in lifespan and reproductive success. The results also suggested that nutrition itself did not affect remating frequency, and that either the rate of egg-laying or the number of sperm in store accounted for differences in remating probability. Females exposed to males that could not transfer sperm also suffered a cost of mating, suggesting that sperm was not costly; so the cost of mating is probably due to mating itself or the transfer of disease, parasites or accessory fluid. One of the accessory fluid sub-components, the sex peptide (SP), has previously been shown to cause an increase in fecundity and a decrease in female sexual receptivity following transfer at mating; it was therefore a candidate for contributing to a cost of receiving accessory fluid. However, whilst the injection of male accessory gland extract into females significantly reduced female lifespan and lifetime reproductive success, there was no evidence to suggest that the SP contributed to this cost. Several experiments explored the possibility of a correlation between the rate of sterile egg-laying and SP-usage in virgin females, as would be predicted if there were receptors for the SP on the ovary, or some other site controlling oviposition rate. There was no evidence to suggest that this was the case. The correlation between the rate of fertile egg-laying and receptivity previously reported for mated females may therefore be an effect of sperm-depletion rates or some other consequence of mating and not of egg-laying <i>per se</i>.