Sperm wars
Promiscuous mice have specialised sperm
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Wednesday, 24, Jan 2007 01:39
Individual sperm in promiscuous rodents are designed so that working together can help them beat their rivals to fertilise females' eggs, a new study has revealed.
Scientists had thought that individual sperm from rats and mice always compete against each other as well as their rivals.
But new research from the University of Sheffield (SU) has found that although sperm tend to work alone in attempting to reach the egg, in some circumstances - particularly in promiscuous females - it can be advantageous for them to cooperate to see off their rivals.
Researchers discovered that rat and mouse sperm have a highly specialised design to enable them to work together.
Promiscuous species have a 'hook shaped' sperm head which helps individual sperm to connect to each other and form a group.
These groups, made up of between five to 100 sperm, are able to swim faster and stronger than individual sperm, giving them a greater opportunity of fertilising the female's egg.
"This research shows that when the pressure from rival males is high, individual sperm will cooperate with one another to ensure that at least one of their siblings successfully reaches the female egg," said Dr Simone Immler from SU's department of animal and plant sciences.
The research is published in the Public Library of Science journal.