Department of Biomedical Sciences, Cornell University, Ithaca, NY, 14853, USA.
Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY, 14853, USA.
Sci Rep. 2017 Jun 9;7(1):3152. doi: 10.1038/s41598-017-03341-4.
From flocking birds to swarming insects, interactions of organisms large and small lead to the emergence of collective dynamics. Here, we report striking collective swimming of bovine sperm in dynamic clusters, enabled by the viscoelasticity of the fluid. Sperm oriented in the same direction within each cluster, and cluster size and cell-cell alignment strength increased with viscoelasticity of the fluid. In contrast, sperm swam randomly and individually in Newtonian (nonelastic) fluids of low and high viscosity. Analysis of the fluid motion surrounding individual swimming sperm indicated that sperm-fluid interaction was facilitated by the elastic component of the fluid. In humans, as well as cattle, sperm are naturally deposited at the entrance to the cervix and must swim through viscoelastic cervical mucus and other mucoid secretions to reach the site of fertilization. Collective swimming induced by elasticity may thus facilitate sperm migration and contribute to successful fertilization. We note that almost all biological fluids (e.g. mucus and blood) are viscoelastic in nature, and this finding highlights the importance of fluid elasticity in biological function.
从成群的鸟类到成群的昆虫，生物个体之间的相互作用导致了集体动力学的出现。在这里，我们报告了牛精子在动态聚集体中惊人的集体游动，这是由流体的粘弹性所实现的。在每个聚集体中，精子朝着相同的方向排列，并且聚集体的大小和细胞间的对准强度随着流体的粘弹性增加而增加。相比之下，在牛顿流体（非弹性）中，低粘度和高粘度的流体中，精子随机游动且个体游动。对单个游动精子周围流体运动的分析表明，精子与流体的相互作用是由流体的弹性成分促进的。在人类和牛中，精子自然沉积在宫颈口入口处，必须通过粘弹性宫颈粘液和其他粘液状分泌物游动才能到达受精部位。由弹性引起的集体游动可能有助于精子迁移并有助于成功受精。我们注意到，几乎所有的生物流体（例如粘液和血液）本质上都是粘弹性的，这一发现强调了流体弹性在生物功能中的重要性。
