Department of Integrative Biology, University of South Florida, Tampa, FL, 33620, USA.
Whitman Center, Marine Biological Laboratory, Woods Hole, MA, 02543, USA.
Sci Rep. 2024 Oct 17;14(1):24374. doi: 10.1038/s41598-024-70999-y.
Free-swimming polychaetes are common in marine habitats and exhibit a unique form of swimming whereby a metachronal wave occurs simultaneously with a bending body wave. This body wave is unusual among swimming animals because it travels in the same direction as the animal's swimming direction. However, we currently lack a mechanistic understanding of this unusual form of locomotion. In this study we use a combination of high-speed, high-resolution video and particle image velocimetry (PIV) to quantify kinematics and fluid dynamics for three species of swimming polychaetes, spanning two orders of magnitude in size. We find that in all species, flows generated by metachronal waves of parapodia dominate while typical flows associated with body bending is absent. However, the parapodia are less flexible than propulsive structures in other metachronal swimmers. This creates a localized, but substantial upstream flow during the recovery stroke. Using body bending, the recovery stroke can occur mostly beneath the bulk flow from the power strokes, resulting in minimal inference while the subsequent power stroke can benefit from the pressure field generated during recovery. These results may have implications for future vehicle designs that incorporate metachronal locomotion.
自由游动的多毛类环节动物在海洋生境中很常见，它们表现出一种独特的游动方式，即同时发生有节奏的波动和身体弯曲波。这种身体波动在游泳动物中很不寻常，因为它的运动方向与动物的游动方向相同。然而，我们目前缺乏对这种不寻常的运动形式的机械理解。在这项研究中，我们使用高速、高分辨率的视频和粒子图像测速（PIV）相结合的方法，对三种游泳多毛类动物的运动学和流体动力学进行了定量分析，这些动物的体型跨越了两个数量级。我们发现，在所有物种中，附肢的有节奏波动产生的流动占主导地位，而与身体弯曲相关的典型流动则不存在。然而，与其他有节奏游动的动物的推进结构相比，附肢的柔韧性较差。这在恢复阶段产生了局部但相当大的上游流动。通过身体弯曲，恢复阶段可以主要发生在动力阶段的主流下方，从而在随后的动力阶段可以受益于恢复阶段产生的压力场，同时最小化对恢复阶段的干扰。这些结果可能对未来采用有节奏运动的车辆设计具有重要意义。
