University of Texas at Austin, Section of Integrative Biology, Austin, TX 78712, USA.
J Evol Biol. 2010 Aug;23(8):1759-71. doi: 10.1111/j.1420-9101.2010.02041.x. Epub 2010 Jul 5.
Species with alternative reproductive strategies are characterized by discrete differences among males in suites of traits related to competition for fertilizations. Models predict sneaker males should allocate more resources to their ejaculates because they experience sperm competition more frequently and often occupy a disfavoured 'role' owing to subordinance in intramale competition and female preferences for larger males. We examined whether sperm number and quality differed between male strategies in the internally fertilized fish Xiphophorus nigrensis and explored the relationship between sperm morphology and performance. We found sneaker males had similar testes sizes compared to courting males but ejaculates with both more viable and longer lived sperm. Sneaker sperm also had longer midpieces, which was positively correlated with both velocity and longevity. Our study suggests that the evolution of sperm quantity and quality can be decoupled and that the sperm morphology is likely to play an important role in mediating sperm competition through its effects on sperm performance.
具有替代繁殖策略的物种的雄性在与争夺受精有关的一系列特征上存在明显差异。模型预测，偷偷交配的雄性应该会将更多的资源分配给它们的精液，因为它们更频繁地经历精子竞争，并且由于在雄性内竞争中处于劣势以及雌性更喜欢更大的雄性，它们往往占据不利的“角色”。我们研究了内部受精的鱼类 Xiphophorus nigrensis 中雄性策略之间的精子数量和质量是否存在差异，并探讨了精子形态和性能之间的关系。我们发现，偷偷交配的雄性与求偶的雄性相比睾丸大小相似，但精液中的精子具有更高的活力和更长的寿命。偷偷交配的精子的中段也更长，这与速度和寿命都呈正相关。我们的研究表明，精子数量和质量的进化可以脱钩，并且精子形态可能通过对精子性能的影响在介导精子竞争中发挥重要作用。
