Gage Matthew J G, Macfarlane Christopher P, Yeates Sarah, Ward Richard G, Searle Jeremy B, Parker Geoffrey A
Centre for Ecology, Evolution, and Conservation, School of Biological Sciences, University of East Anglia, NR4 7TJ, Norwich, United Kingdom.
Curr Biol. 2004 Jan 6;14(1):44-7.
Sperm competition occurs when sperm from more than one male compete for fertilizations. This form of post-copulatory sexual selection is recognized as a significant and widespread force in the evolution of male reproductive biology and as a key determinant of differential male reproductive success. Despite its importance, however, detailed mechanisms of sperm competition at the gamete level remain poorly understood. Here, we use natural variation in spermatozoal traits among wild Atlantic salmon (Salmo salar), a species naturally adapted to sperm competition, to examine how the relative influences of sperm (i) number, (ii) velocity, (iii) longevity, and (iv) total length determine sperm competition success. Atlantic salmon fertilize externally, and we were therefore able to conduct controlled in vitro fertilization competitions while concurrently measuring spermatozoal traits within the aqueous micro-environment to which salmon gametes are naturally adapted. Microsatellite DNA fingerprinting revealed that a male's relative sperm velocity was the primary determinant of sperm competition success. There was no significant relationship between fertilization success and either relative sperm number or total length; sperm longevity showed an inverse relationship with competition success. These relationships were consistent for two experimental repeats of the in vitro fertilization competitions. Our results therefore show, under the natural microenvironment for salmon gametes, that relative sperm velocity is a key spermatozoal component for sperm competition success. Atlantic salmon sperm can be considered to enter a competition analogous to a race in which the fastest sperm have the highest probability of success.
当来自多个雄性的精子竞争受精时，就会发生精子竞争。这种交配后的性选择形式被认为是雄性生殖生物学进化中的一种重要且广泛存在的力量，也是雄性生殖成功差异的关键决定因素。然而，尽管其很重要，但配子水平上精子竞争的详细机制仍知之甚少。在此，我们利用野生大西洋鲑（Salmo salar）精子特征的自然变异来研究精子（i）数量、（ii）速度、（iii）寿命和（iv）全长的相对影响如何决定精子竞争的成功，大西洋鲑是一种自然适应精子竞争的物种。大西洋鲑进行体外受精，因此我们能够进行可控的体外受精竞争，同时在鲑鱼配子自然适应的水性微环境中测量精子特征。微卫星DNA指纹分析表明，雄性的相对精子速度是精子竞争成功的主要决定因素。受精成功率与相对精子数量或全长之间均无显著关系；精子寿命与竞争成功率呈负相关。体外受精竞争的两次实验重复中，这些关系都是一致的。因此，我们的结果表明，在鲑鱼配子的自然微环境下，相对精子速度是精子竞争成功的关键精子组成部分。可以认为大西洋鲑精子进入了一场类似于赛跑的竞争，跑得最快的精子成功概率最高。
