size or number?
These observations allow them to reach two conclusions. First, the fight for reproduction for males involves producing a sperm quality to fertilize up to females.
The researchers explain that this means either the production of large sperm or the production of a large quantity of gametes. Males should make a choice between size and number because their body can not produce gametes benefiting from these two characteristics at once.
In non-monogamous species, where competition for females is intense, as in mice, the scientists note that sperm production results in large gametes.
Selection process
Other discovery, the researchers note that over the female reproductive system has a large, more males will seek to produce many gametes, to the detriment of their size.
They give the example of the elephant: risks for sperm are lost and do not reach the ovules are high, because the female reproductive tract are particularly large. To compensate for this loss, the elephant gametes produced many but small.
In mice, however, the sperm is little way to go. The males can then invest in the size of the gametes, which will be more effective to fertilize females. With always a ojectif, that transmit their hereditary traits to future generations.
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