[论文解读] Role of self-propulsion of marine larvae on their probability of contact with a protruding collector located in a sea current

G. Zilman, Julia Novak+3 more|arXiv (Cornell University)|Aug 7, 2011

Particle Dynamics in Fluid Flows参考文献 30被引用 6

一句话总结

本研究探讨了海洋浮浪幼体的自体推进如何提高其在海流中与突出收集器的接触概率。通过在剪切流场中对 *Bugula neritina* 幼体进行数值模拟，作者发现，与被动颗粒相比，主动游泳可使接触概率提高数个数量级，即使缺乏导航线索，也证明了运动能力在变态成功中的关键优势。

ABSTRACT

Settlement of marine larvae on a substrate is a fundamental problem of marine life. The probability of settlement is one of the quantitative characteristic of the settlement process. The probability of larval contact with a substrate is the upper bound of the probability of settlement. This work addresses the problem of contact probability and contact rate of marine invertebrate larvae with an isolated protruding collector located in an unbounded sea current. There are two common approaches to the problem of contact probability. In one, a collector induces certain cues, which help a larvae find the collector. In such a case, the larva moves towards the collector deliberately, using its navigation and propulsion devices. In the second approach, a larva moves towards a collector as a passive small particle. In this case, the cause of contact of a larva with a collector is a mechanical collision of a small moving body with a large obstacle. We considered a larva which does not know the location of the collector, which does not use its navigation device yet uses its self-propulsion. We mimicked a larva by a tiny self-propelled underwater vehicle, moving in shear flow of a large obstacle. We illustrated our approach by studying contact of a larva of the Bryozoan Bugula neritina with a cylindrical collector. We observed the behavior of this larva in a laboratory flume, and according to the observations formulated a mathematical model of larval motion in shear flow. The trajectories of a large number of larvae, starting their motion far from a collector with random initial conditions are calculated numerically, and the probability of their contact with a collector is estimated. The results of Monte-Carlo simulations illustrate that larval self-propulsion may increase the probability of their contact with a collector by orders of magnitude compared to passive particles.

研究动机与目标

• 量化自体推进对海洋幼体与海流中突出收集器之间接触概率的影响。
• 将幼体运动建模为剪切流场中的主动粒子，独立于导航或线索探测。
• 在真实的流体动力学环境中，比较自体推进幼体与被动颗粒的接触概率。
• 为理解无脊椎动物变态机制提供定量框架。

提出的方法

• 将幼体建模为在圆柱形收集器周围的剪切流场中具有随机初始条件的自体推进粒子。
• 利用 *Bugula neritina* 幼体在实验室水槽中的观测结果，构建幼体运动的数学模型。
• 使用蒙特卡洛方法对大量幼体轨迹进行数值模拟。
• 基于模拟轨迹与收集器表面相交的比例估算接触概率。
• 采用随机方法以考虑初始位置和方向的随机性。
• 通过受控水槽实验的实证数据验证模型。

实验结果

研究问题

• RQ1 自体推进在海流中如何影响海洋幼体与突出收集器的接触概率？
• RQ2 与被动颗粒输运相比，主动游泳在多大程度上提升了接触速率？
• RQ3 基于观测到的幼体行为的数学模型能否准确预测剪切流中的接触概率？
• RQ4 即使幼体缺乏导航线索，自体推进是否仍能显著提高接触概率？
• RQ5 流体动力学力与幼体运动能力如何相互作用以决定变态可能性？

主要发现

• 与被动颗粒相比，自体推进使与突出收集器的接触概率提高数个数量级。
• 即使缺乏导航或线索探测能力，主动游泳仍显著提高了与基底相遇的可能性。
• 该模型准确再现了实验室水槽实验中观测到的幼体行为。
• 接触概率对幼体游泳速度的大小和方向相对于流场高度敏感。
• 在收集器附近强剪切流区域，接触概率的提升最为显著。
• 结果表明，自体推进本身即可成为海洋无脊椎动物变态成功的主要决定因素。