Female Drosophila melanogaster with environmentally or genetically elevated rates of mating die younger than controls. This cost of mating is not attributable to receipt of sperm. We demonstrate here that seminal fluid products from the main cells of the male accessory gland are responsible for the cost of mating in females, and that increasing exposure to these products increases female death rate. Main-cell products are also involved in elevating the rate of female egg-laying, in reducing female receptivity to further matings and in removing or destroying sperm of previous mates. The cost of mating to females may therefore represent a side-effect of evolutionary conflict between males.

Cost of mating in Drosophila melanogaster females is mediated by male accessory gland products

Many genes that mediate sexual reproduction, such as those involved in gamete recognition, diverge rapidly, often as a result of adaptive evolution This widespread phenomenon might have important consequences, such as the establishment of barriers to fertilization that might lead to speciation Sequence comparisons and functional studies are beginning to show the extent to which the rapid divergence of reproductive proteins is involved in the speciation process

The rapid evolution of reproductive proteins.

EACH sex is part of the environment of the other sex. This may lead to perpetual coevolution between the sexes, when adaptation by one sex reduces fitness of the other. Indirect evidence comes from experiments with Drosophila melanogaster indicating that seminal fluid reduces the competitive ability of sperm from other males, thereby increasing male fitness1,2. It also reduces a female's propensity to remate and increases her egg-laying rate3. In contrast to these benefits to males, seminal fluid has substantial toxic side effects in females, with increasing quantity leading to decreasing female survival4,5. Here I show that when female D. melanogaster are experimentally prevented from coevolving with males, males rapidly adapt to the static female phenotype. This male adaptation leads to a reduction in female survivorship, which is mediated by an increased rate of remating and increased toxicity of seminal fluid.

Sexually antagonistic male adaptation triggered by experimental arrest of female evolution

Secretions of male accessory glands contain a variety of bioactive molecules. When transferred during mating, these molecules exert wide-ranging effects on female reproductive activity and they improve the male's chances of siring a significant proportion of the female's offspring. The accessory gland secretions may affect virtually all aspects of the female's reproductive activity. The secretions may render her unwilling or unable to remate for some time, facilitating sperm storage and ensuring that any eggs laid will be fertilized by that male's sperm. They may stimulate an increase in the number and rate of development of eggs and modulate ovulation and/or oviposition. Antimicrobial agents in the secretions ensure that the female reproductive tract is a hospitable environment during sperm transfer. In a few species the secretions include noxious chemicals. These are sequestered by developing eggs that are thereby protected from predators and pathogens when laid.

Male accessory gland secretions: modulators of female reproductive physiology and behavior.

The female reproductive tract is where competition between the sperm of different males takes place, aided and abetted by the female herself Intense postcopulatory sexual selection fosters inter-sexual conflict and drives rapid evolutionary change to generate a startling diversity of morphological, behavioural and physiological adaptations We identify three main issues that should be resolved to advance our understanding of postcopulatory sexual selection We need to determine the genetic basis of different male fertility traits and female traits that mediate sperm selection; identify the genes or genomic regions that control these traits; and establish the coevolutionary trajectory of sexes

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P.S. Chen

Papers

A male accessory gland peptide that regulates reproductive behavior of female D. melanogaster

A male accessory gland peptide with protease inhibitory activity in Drosophila funebris