有关精子之间的竞争和合作都已有很多研究，但不同精子是否能将它们应当与之合作的“亲兄弟”跟它们不应与之合作的“非亲兄弟”区分开来？
Heidi Fisher 和 Hopi Hoekstra发现，当两个种的鹿鼠的精子相混时，它们优先与来自其自己所属种的精子聚集。当同一个种的不同个体混在一起时，来自单配（即一雌一雄）种的精子不区分“亲兄弟”与“非亲兄弟”，而来自混交种的精子则进行这种区分。
生物谷推荐原始出处：
Nature doi:10.1038/nature08736;
Competition drives cooperation among closely related sperm of deer mice
Heidi S. Fisher1,2 " Hopi E. Hoekstra1,2
Department of Organismic and Evolutionary Biology, Museum of Comparative Zoology,Center for Brain Science, Harvard University, Cambridge, Massachusetts 02138, USA
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.
