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

海鞘是一种远洋的、桶状的、喷射推进的游泳者，它们对小颗粒（1米- 1毫米）的过滤速度比几乎任何其他浮游食草动物都要高。在热带和亚热带海洋中发现了大多数salp物种，它们在有机物质的循环中起着关键作用。了解它们的游泳行为和滤食机制对于梳理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，海鞘进食和运动的耦合导致了这两个生命过程之间的权衡。这群动物的特点是形态和游泳行为的多样性，这可能与共生物种的生态作用有关。初步数据表明，形态上的差异可能解释了海鞘从快游形态到慢游形态的一系列生活方式。与速度较慢、面向表面的海鞘相比，快速游动的海鞘具有增强的肌肉组织、更高的脉搏率和线性、流线型的链结构。本研究将研究巴拿马太平洋沿岸的salp物种的游泳和摄食行为，并利用这些信息来绘制形态，游泳力学和生态角色之间的联系。该方法将结合现场和实验室方法，从微观过滤装置到动物周围的流场。这项工作将集中在快速游泳的流线型水藻（Salpa圆柱形）、慢速游泳的白藻（Pegea confoederata）和慢速游泳的轮状聚集体水藻（Cyclosalpa spp）。该项目的具体目标是：a)量化在野外和实验室中游动的海鞘产生的水流，并检查水流与进料效率之间的联系；b)用三维视频描述整个滤网的形式和运动；c)在微观上测量滤网参数，以描述过滤的小尺度力学。关于胶状食草动物向海洋深处运送大量物质的知识越来越多，但我们缺乏关于生态功能和个体物种关系的信息。新技术的应用将为salp物种之间过滤速率和颗粒保留效率的变化提供机制基础。这项工作将增强我们对海鞘进化形式多样性的理解，以及它与其他浮游食草动物共存的更广泛关系。拟议工作的更广泛影响包括培养一名研究生（博士）和两名本科生。研究生将学习显微镜、流体力学和处理脆弱浮游生物的方法。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质动物群的研究将吸引公众，我们已经联系了WHOI的Oceanus杂志的编辑，准备发表我们的发现。该杂志的网络版每月有3万次点击量，每期印刷6500份。

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.