动物行为研究的新进展(八):精子竞争

New advance on study of animal behavior(Ⅷ):sperm competition

以粪蝇、黑翅豆娘、岩鹨、鲨鱼和海胆等各种动物为实例介绍了动物行为学中比较新的概念，即精子竞争理论。在某些混交制的交配体制中，雄性个体不仅要竞争与雌性个体的交配权，而且还要竞争其精子使卵受精的机会。在这种情况下，自然选择就会直接对动物的行为、精子的形态和大小等各种特征发挥作用，使精子处于强大的自然选择压力下。为了获得精子竞争的胜利，黑翅豆娘进化出了极其特殊的形态结构，一只正在交配的雄豆娘的交接器会像—把丛刷—样把雌豆娘贮精囊中90％～100％的精子抽吸出来，然后才把自己的精子释放到雌豆娘体内。这些精子将会贮存在此前已被彻底腾空了的贮精囊内，供雌豆娘为其卵受精之用。在精子竞争中，雌性个体不只是简单地扮演一个只能接受雄性个体精子的不重要的角色，实际上，它通过配偶选择也发挥着积极的作用，这是目前动物行为学中—个十分活跃的研究领域。

In this paper, we will introduce the effect of sperm competition--that is, the direct competition between the sperm of different males to fertilize a female＇s eggs--on mating success and the evolution of mating systems. In some promiscuous and some polyandrous mating systems, males compete not only for access to mating opportunities with females, but directly for access to eggs. In these systems, competition occurs after a female has mated with numerous males. If females store sperm from numerous matings, sperm from different males may compete with one another over access to fertilizable eggs. When sperm competition exists, selection can operate directly on various attributes of sperm, such as sperm size and shape. If a male wins a physical fight with the opponents, this may provide him access to an estrous female that may lead to a mating opportunity, which may result to fertilization.