Female Mammals May Select Out Competing Sperm

There's new evidence that the reproductive tract favors one mate over another

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FRIDAY, Nov. 30, 2007 (HealthDay News) -- Scientists may have proof that female mammals' reproductive systems detect the presence of sperm and react by changing conditions in the uterus.

An international team of researchers say this may be the molecular mechanism behind post-copulatory sexual selection, where females who've mated with several partners can actually influence which sperm fertilizes the egg.

Learning more about this post-mating "ladies choice" may have important implications for in-vitro fertilization (IVF), cloning and animal breeding, according to study author Alireza Fazeli, of the University of Sheffield in the U.K. It also provides a possible explanation for female promiscuity in certain species.

In this study, Fazeli and colleagues found chemical evidence of a sperm-recognition system in the oviducts of female pigs, who have a reproductive system that's similar to humans.

"This study clearly shows that the sperm's arrival in the female reproductive tract triggers a cascade of changes that leads to alteration of protein production in [the] oviduct and a change in oviductal environment. We speculate that this is mainly done to prepare oviduct environment for storing sperm, fertilization and early embryonic development," Fazeli said in a prepared statement.

This can also be used as a detection and selection system that alerts the female to different kinds of sperm, triggering oviduct mechanisms that control sperm transport, binding and activation for fertilization.

"We know sperm selection exists in nature, especially in promiscuous species, when females mate with several males. Baboons are a good example. During one reproductive cycle, if the female mates with several males, most of the time the offspring belong to one of the males -- not a spread between all of them. We are now seeing what can be the molecular basis for this effect," Fazeli said.

More information

Learn more about female reproduction at the American Medical Association.

SOURCE: American Chemical Society, news release, November 2007

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