sperm cooperation

By forming cooperative groups, sperm can increase their swimming velocity and thereby gain an advantage in intermale sperm competition
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We find that sperm aggregate more often with conspecific than heterospecific sperm, suggesting that individual sperm can discriminate on the basis of genetic relatedness.
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These results suggest that sperm from promiscuous deer mice discriminate among relatives and thereby cooperate with the most closely related sperm, an adaptation likely to have been driven by sperm competition.

- Competition drives cooperation among closely related sperm of deer mice

via larvatus prodeo