Swimming spermatozoa from diverse organisms often have very similar morphologies, yet different motilities as a result of differences in the flagellar waveforms used for propulsion. The origin of these differences has remained largely unknown. Using high-speed video microscopy and mathematical analysis of flagellar shape dynamics, we quantitatively compare sperm flagellar waveforms from marine invertebrates to humans by means of a novel phylokinematic tree. This new approach revealed that genetically dissimilar sperm can exhibit strikingly similar flagellar waveforms and identifies two dominant flagellar waveforms among the deuterostomes studied here, corresponding to internal and external fertilizers. The phylokinematic tree shows marked discordance from the phylogenetic tree, indicating that physical properties of the fluid environment, more than genetic relatedness, act as an important selective pressure in shaping the evolution of sperm motility. More broadly, this work provides a physical axis to complement morphological and genetic studies to understand evolutionary relationships.

中文翻译：

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鞭毛运动学揭示环境在塑造精子活力中的作用

来自不同生物体的游泳精子通常具有非常相似的形态，但由于用于推进的鞭毛波形不同而具有不同的运动性。这些差异的起源在很大程度上仍然未知。使用高速视频显微镜和鞭毛形状动力学的数学分析，我们通过一种新的系统运动树定量比较了从海洋无脊椎动物到人类的精子鞭毛波形。这种新方法表明，基因不同的精子可以表现出惊人相似的鞭毛波形，并在这里研究的氘口中识别出两种主要的鞭毛波形，对应于内部和外部肥料。系统运动树显示出与系统发育树的明显不一致，表明流体环境的物理特性，不仅仅是遗传相关性，在塑造精子活力的进化过程中，它还是一种重要的选择压力。更广泛地说，这项工作提供了一个物理轴来补充形态学和遗传学研究，以了解进化关系。