Credit: iStockphoto/Serdad YagciA research team at Uppsala University in Sweden, has found that unfaithful females influence its size and speed....
The international team's findings, to be published in the Proceddings of the National Academy of Sciences, showed that competition among sperm to fertilize the eggs of unfaithful females has evolved into larger and faster sperm.
Twenty-nine species of cichlid fish were studied, with female mating habits ranging from monogamous to promiscuous. Cichlid fish are found in Lake Tanganyika and lakes nearby, in central Africa.
Size and speed of male sperm were measured after mating with monogamous female cichlid fish. The same males were then moved to an area with promiscous female cichlids, and during that period the cichlid sperm became faster and larger, in that order. The researchers concluded that these changed evolved because the sperm, having rival suiters, had become comptetitive with the sperm of other fish.
This is the first study, according to the researchers, that showed that 'size does count."
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