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University research aims to solve major questions in reproductive biology
An expert at the University of Sheffield is set to investigate whether all sperm males produce are equally likely to fertilise, as part of a £1.7million research project that could lead to improvements in assisted reproductive technology in humans.
Professor Tim Birkhead, from the University´s Department of Animal and Plant Sciences, will look at the biological significance of the size and number of sperm different species produce, as well as how species apportion their reproductive resources to suit their environment.
It has long been known that female whales have an enormous oviduct which can result in sperm getting lost going through it, otherwise known as the dilution effect. In contrast, the oviduct of a mouse is much smaller so there is less risk of dilution being an issue. The research will use sperm found in the faeces of birds as a model to identify how species compensate for the dilution effect by adjusting the size of their sperm.
The other aspect of reproduction the project will investigate will be the process of sperm production depending on the degree of promiscuity. Previous research by Professor Birkhead has suggested that the males of promiscuous species tend to produce larger, more sophisticated sperm which can swim faster. In contrast, strictly monogamous species have no need to invest in their sperm quality to the same extent and as a result produce smaller, less sophisticated sperm, because of the lack of competition from other males. The new study will test this theoretical idea and investigate the energetic costs of making sperm.
It is hoped the findings of Professor Birkhead´s project, which has been funded by a prestigious five-year European Research Council (ERC) grant, will help resolve some of these major questions in reproductive biology and in turn have implications for assisted reproductive technology for humans.
Professor Birkhead said: "Intracytoplasmic (IC SI) sperm injection, is the most frequently used technique in assisted reproduction, and works on the assumption that all sperm are more or less equal. However, there is increasing evidence that the children produced by IC SI have reproductive problems themselves. If my research confirms that all sperm are not equal, the findings could be applied to humans to avoid the problems from IC SI by identifying sperm that are good fertilisers and produce healthy embryos and adults."
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