In what may help better the understanding of infertility in humans, University of Liverpool researchers have found that field mice have evolved a unique way of ensuring faster fertilisation.
Working in collaboration with Charles University, Prague, the researchers found that field mice sacrifice some of their immunity protection in favour of a more rapid fertilisation process.
This, according to them, happens because of the absence of a protein called CD46, which is present in animals as well as humans. The CD46 protein helps protect the body's cells from attack by its immune system.
The researchers say that over time, field mice have lost the ability to produce this protein, leading to instability of a cap-like structure known as acrosome, which is present over the head of the sperm.
Such an instability enabled the acrosome to be shed from the sperm head to create a new surface essential for sperm to be capable of fusing with an egg.
While this natural process can take days to occur in humans, field mice have developed a way by which this can occur rapidly.
Immunologist, Professor Peter Johnson, says: "Field mice have traded the production of an immunologically important protein in favour of this faster fertilization process in order to compete with other mice more successfully. Female mice produce multiple eggs and if there are a lot of male mice competing for her, then it is an advantage to an individual mouse for its sperm to react quickly in order to beat other male competitors to fertilisation."
"By improving our understanding of defects in CD46 we may improve treatments for infertility in men. Humans normally produce a single egg each month and there is no evolutionary necessity to develop rapid sperm reaction to egg fertilisation. The process is therefore much slower and so any defect in CD46 could result in sperm being destabilised too early.
"Interestingly the rapid reaction caused in mice is similar to that in IVF treatment in humans where the acronome is artificially expelled from the sperm head before it is introduced to the egg to speed up the fertilisation process. Field mice appear to do this naturally," Johanson adds.
The research has been reported in the journal Reproduction.