Form, Function and Flow in the Plankton: Jet Propulsion and Filtration by Pelagic Tunicates

Salps是一种深海、桶形、喷气推进的游泳者，其对小颗粒(1 m-1 mm)的滤过率比几乎任何其他浮游食草动物都要高。大多数盐类物种分布在海洋、热带和亚热带水域，在这些水域中，它们在有机物质的循环中发挥着关键作用。了解它们的游泳行为和滤食机制，对于梳理出这些重要食草动物的生态作用至关重要。在喷气推进过程中，SAPS的取食和运动的耦合导致了这两个生命过程之间的权衡。这组动物的特征是形态和游泳行为的多样性，这可能与共存物种的生态作用有关。初步数据表明，形态差异可能解释了从快速游泳形式到较慢游泳形式的一系列生活方式。与速度较慢、面向表面的海水相比，快速游泳的海水具有更强的肌肉组织、更高的脉搏频率和线性、流线型的链状结构。这项研究将研究巴拿马太平洋沿岸存在的海水物种的游泳和摄食行为，并利用这些信息得出形态、游泳机制和生态作用之间的联系。该方法将结合现场和实验室的方法，从微观过滤设备到动物周围的流场。这项工作将集中在Salpa Cylindrica，一种快速、流线型的游泳形式，Pegea confoederata，一种游泳速度较慢的形式，以及Cylosalpa spp.，一种具有轮状聚集体的慢游泳形式。该项目的具体目标是a)量化田间和实验室中的鱼塘产生的水的流量，并检查流量和进料效率之间的关系，b)用三维视频描述整个滤网的形状和运动，以及c)通过显微镜测量滤网参数，以描述过滤的小尺度机理。关于胶状食草动物向海洋深处大量运输物质的知识越来越多，但我们缺乏关于个别物种的生态功能和关系的信息。新技术的应用将为不同盐碱地物种之间的过滤速率和颗粒保留效率的差异提供一个机械基础。这项工作将加强我们对Salp中存在的形式的进化多样性以及它如何更广泛地与其他浮游生物共存的关系的理解。拟议工作的广泛影响包括培养一名研究生(Ph.D.)和两名本科生。这位研究生将发展显微镜、流体力学和处理脆弱浮游生物的方法方面的技能。本科生将获得实地和实验室的研究经验。在原始环境中对大型胶状动物的研究将吸引公众，我们已经就发表我们的发现联系了世界卫生组织《海洋》杂志的编辑。该杂志的网络版每月点击量为30,000次，每期发行6,500份印刷版。

Salps are pelagic, barrel-shaped, jet-propelled swimmers that have higher filtering rates of small particles (1 m- 1 mm) than almost any other planktonic grazer. The majority of salp species are found in oceanic tropical and subtropical waters where they play a critical role in cycling of organic material. An understanding of their swimming behavior and filter feeding mechanics is critical to teasing out the ecological roles of these important grazers. The coupling of feeding and locomotion by salps during jet propulsion results in trade-offs between these two life processes. This group of animals is characterized by a diversity of morphology and swimming behaviors, that likely relate to ecological roles of co-occuring species. Preliminary data indicate that morphological differences may account for a range of lifestyles among salps from fast swimming forms to slower swimming forms. Fast swimming salps are characterized by enhanced musculature, higher pulse rates and linear, streamlined chain structures compared to slower, surface oriented salps.This study will examine the swimming and feeding behavior of salp species present off the Pacific Coast of Panama and use this information to draw linkages between morphology, swimming mechanics and ecological roles. The approach will combine field and laboratory methods that span scales from the microscopic filtering apparatus to the flow field around the animal. The work will focus on Salpa cylindrica, a fast-swimming, streamlined form, Pegea confoederata, a slower swimming form and Cyclosalpa spp., a slow swimming form with wheel shaped aggregates. The specific goals of this project are to a) quantify the flow of water produced by swimming salps in the field and in the lab and examine the connection between flow and feeding efficiency, b) describe the form and movement of the entire filtering mesh with 3-dimensional video and, c) measure filtering mesh parameters microscopically in order to describe the small-scale mechanics of filtration. There is increasing knowledge of the substantial transport of material to the ocean's deep interior by gelatinous grazers but we lack information about the ecological function and relationships of individual species. The application of new techniques will provide a mechanistic basis for variations in filtering rates and particle retention efficiencies among salp species. This work will enhance our understanding of the evolutionary diversity of form present in salps and how it relates more broadly to the coexistence of other planktonic grazers.Broader impacts of the proposed work include the training of one graduate student (Ph.D.) and two undergraduate students. The graduate student will develop skills in microscopy, fluid mechanics and methods for working with fragile planktonic organisms. Undergraduate students will gain research experience both in the field and the laboratory. The study of large gelatinous fauna in a pristine setting will be appealing to the public and we have already contacted the editors of WHOI's Oceanus magazine about publishing our findings. The online version of the magazine receives 30,000 hits each month and 6,500 print copies of each issue are distributed.