Functional Consequences of Being Multicellular: Predation by Protozoans on Unicellular vs. Multicellular Choanoflagellates

动物的身体由许多细胞组成，但动物的祖先是单细胞生物（“原生动物”）。 生命进化的关键一步是从单细胞到多细胞的转变。 与动物关系最近的原生动物是水生的“领鞭毛虫”，它们是单细胞的，但也可以形成多细胞的群落。 对于多细胞生物的进化，动物祖先的群体必须比单个细胞更好地发挥影响其生存的功能。 本研究探讨了单细胞或多细胞的choanoflagellates是否能够更好地避免被原生动物捕食者吃掉，以及所涉及的机制。 这个项目在生物学和物理学之间的接口（水生捕食者和猎物如何相互作用的流体动力学）将为来自不同专业的本科生团队提供实践研究经验，并将使他们参与跨学科研究，这很重要，因为许多未来的科学发现和技术将在不同领域之间的接口。公众宣传包括一个互动的在线网站，公民科学家可以计算不同类型的捕食者对单细胞和多细胞领鞭毛虫的捕食率。项目研究员与妇女和诵读困难者一起工作将鼓励在科学和技术领域取得成功。将开发一种新的微流体系统，以确定捕食者-猎物相互作用（通常在静水中研究）的性能和机制如何受到微观游泳者在自然湍流水流中经历的波动剪切的现实模式的影响。 该系统对研究自然界中其他水生微生物之间的相互作用具有一定的参考价值。原生动物，无论是单细胞的还是群体的，在水生食物网中都扮演着重要的角色。 Chonaoflagellates是动物最接近的原生动物亲属，将用于研究单细胞与多细胞原生动物抵抗捕食的机制。 有关choanoflagellates的数据也将使知情的推断捕食作为一个选择性因素在多细胞生物的进化可能发挥的作用。 从单细胞原生动物到多细胞动物的起源代表了生命史上的一个关键转变。 这项研究的重点是抵抗被原生动物捕食者吃掉（在动物进化之前，chonaoflagellates上的捕食者是其他原生动物）。 研究目标是：1）定量分析单细胞和群体领鞭毛虫在不同捕食模式下躲避原生动物捕食的能力差异，2）阐明捕食者与领鞭毛虫捕食者之间相互作用的流体动力学，以确定其能力差异的机制;第三章确定自然界中原生动物在湍流水流中遇到的波动剪切如何影响单细胞与殖民地的相互作用被捕食者捕食 高速视频显微摄影的捕食者，猎物，和流动标记微珠将记录的choanoflagellates与不同的原生动物捕食者的相互作用。数字化的原生动物轨迹可以计算遭遇和捕食成功率以及行为相互作用。粒子跟踪测速技术将量化捕食者和猎物产生的瞬时流场，以及它们相互作用期间的流体动力学信号。 一个新的贡献是微流控技术的发展，以确定捕食者-猎物的相互作用（通常在静水中研究）的机制是如何受到现实模式的波动剪切，微观游泳者在湍流环境水流的经验。

Animal bodies are made up of many cells, but the ancestors of animals were single-celled organisms ("protozoans"). A pivotal step in the evolution of life was the transition from being unicellular to becoming multicellular. The closest protozoan relatives of animals are aquatic "choanoflagellates", which are unicellular but can also form multicellular colonies. For multicellularity to evolve, colonies of animal ancestors must have performed functions affecting their survival better than did solitary cells. This study examines whether unicellular or multicellular choanoflagellates are better able to avoid being eaten by protozoan predators, and the mechanisms involved. This project at the interface between biology and physics (hydrodynamics of how aquatic predators and prey interact) will give teams of undergraduate students from different majors hands-on research experience and will involve them in interdisciplinary research, which is important because many future discoveries in science and technology will be made at interfaces between different fields. Public outreach includes an interactive online site where citizen scientists can calculate the predation rates on unicellular and multicellular choanoflagellates by different types of predators. Work with women and dyslexics by the PIs will encourage success in science and technology fields. A novel microfluidic system will be developed to determine how performance and mechanisms of predator-prey interactions (usually studied in still water) are affected by realistic patterns of fluctuating shear that microscopic swimmers experience in natural, turbulent water flow. This system will be useful for studying other aquatic microoganisms interacting with each other in nature. Protozoans, both unicellular and colonial, play important roles in aquatic food webs. Chonaoflagellates, the closest protozoan relatives of animals, will be used to study mechanisms underlying resistance to predation by uni- vs. multicellular protozoans. Data about choanoflagellates will also enable informed inferences about the possible role of predation as a selective factor in the evolution of multicellularity. The origin of multicellular animals from unicellular protozoans represents a pivotal transition in life's history. This study focuses on resistance to being eaten by protozoan predators (before animals evolved, predators on chonaoflagellates were other protozoans). Research goals are to: 1) quantify performance differences between unicellular and colonial choanoflagellates in avoiding predation by protozoan predators using different modes of prey capture; 2) elucidate fluid dynamics of interactions between predators and choanoflagellate prey to identify mechanisms underlying performance differences; 3) determine how fluctuating shear encountered by protozoans carried in turbulent water flow in nature affects interactions of unicellular vs. colonial prey with predators. High-speed videomicrography of predators, prey, and flow-marking microbeads will record interactions of choanoflagellates with different protozoan predators. Digitized protozoan trajectories enable calculation of encounter and predation success rates, and behavioral interactions. Particle tracking velocimetry will quantify instantaneous flow fields produced by predators and prey, and hydrodynamic signals during their interactions. A novel contribution is development of microfluidic techniques to determine how mechanisms of predator-prey interactions (usually studied in still water) are affected by realistic patterns of fluctuating shear that microscopic swimmers experience in turbulent ambient water flow.