具有亲属关系的动物会互助是常见现象，而《自然》杂志网站20日刊登的一项最新研究显示，精子之间也存在这种行为，相同来源的精子会像火车车厢一样彼此连在一起，从而加快向前游进的速度。

美国哈佛大学研究人员报告说，如果将两种实验鼠的精子混合在一起，那么相同来源的精子就会利用其头部的钩状物互相连接起来，协力向前游动，这样一列“精子火车”的速度比单个精子要快约50％，四分之三相同来源的精子都会加入这样的队列中。

精子之间的互助行为还不止于此，在一列“精子火车”中，会有一些精子提前启动与卵子进行反应的机制，这一行为会加速整个“列车”的速度，但是也会导致前者提前死亡。虽然最终只有一个精子能与卵细胞结合，但如果是同一来源的精子胜出，一些精子的自我牺牲行为便体现了价值。

哈佛大学研究人员在下一阶段将关注精子是采取何种方式来进行彼此间的身份识别。

原始出处：

Nature advance online publication 20 January 2010 | doi:10.1038/nature08736

Competition drives cooperation among closely related sperm of deer mice

Heidi S. Fisher1,2 & Hopi E. Hoekstra1,2

1 Department of Organismic and Evolutionary Biology, Museum of Comparative Zoology,
2 Center for Brain Science, Harvard University, Cambridge, Massachusetts 02138, USA
Correspondence to: Heidi S. Fisher1,2 Correspondence and requests for materials should be addressed to H.S.F.

Among the extraordinary adaptations driven by sperm competition is the cooperative behaviour of spermatozoa1. By forming cooperative groups, sperm can increase their swimming velocity and thereby gain an advantage in intermale sperm competition1, 2. Accordingly, selection should favour cooperation of the most closely related sperm to maximize fitness3. Here we show that sperm of deer mice (genus Peromyscus) form motile aggregations, then we use this system to test predictions of sperm cooperation. We find that sperm aggregate more often with conspecific than heterospecific sperm, suggesting that individual sperm can discriminate on the basis of genetic relatedness. Next, we provide evidence that the cooperative behaviour of closely related sperm is driven by sperm competition. In a monogamous species lacking sperm competition, Peromyscus polionotus, sperm indiscriminately group with unrelated conspecific sperm. In contrast, in the highly promiscuous deer mouse, Peromyscus maniculatus, sperm are significantly more likely to aggregate with those obtained from the same male than with sperm from an unrelated conspecific donor. Even when we test sperm from sibling males, we continue to see preferential aggregations of related sperm in P. maniculatus. 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.