DISSERTATION RESEARCH: Feast or Flee: How do Microzooplankton Detect and Avoid Predators?

动物从捕食者和猎物那里感受到大量的触觉、嗅觉、视觉和听觉信号，整合这些信号，并做出适当的行为反应；分别是躲避和捕获猎物。了解动物如何整合这些多种信号来唤起复杂的行为是行为生物学的核心挑战之一。在细胞水平上，单细胞真核生物与多细胞动物具有许多相同的感觉特征，因此在概念和功能上提供了高等生物的感觉和行为特征的极好类似物。研究人员将使用海洋微型浮游动物纤毛虫Favella sp.作为模式生物来研究感觉机制，使它们能够感知和整合来自捕食者和猎物的线索，从而在成功捕获猎物的同时避免被捕食。因为这些单细胞生物代表了早期进化的真核生物群体，表征它们的感觉能力将为了解多细胞生物中综合细胞信号传导和突现行为特征的进化提供见解。此外，了解这些微型浮游动物（一组负责消耗约60%的海洋初级生产力的生物）之间的捕食者-猎物相互作用，将有助于更好地了解它们在支持海洋食物网和海洋表层营养物质流动方面所起的作用。这两个更大的生态系统尺度过程对海洋生态系统服务（如渔业）和影响我们气候的生物地球化学循环都有影响。除了这些重要的科学问题外，拟议的研究还将促进研究生与微型浮游动物生态学专家的跨学科合作。促进科研人员的专业培训、科学传播和职业发展，并支持其参加高水平的科学会议。该奖项还将允许研究人员进一步开发和实施针对高中生的教学计划，这将有助于吸引他们学习大学水平的科学和技术课程，并激励他们作为本科生参与研究。微型浮游动物肺泡（纤毛虫和鞭毛藻）将大量能量从初级生产转移到较大的后生动物消费者。在这些捕食者-猎物相互作用的基础上是复杂的行为，这些行为使它们能够通过感知和整合来自彼此的各种刺激来有效地捕获首选猎物并逃避捕食。尽管这些行为相互作用在生态学上具有重要意义，但之前没有研究调查过微型浮游动物是如何在接收到相似类型的感觉信息的情况下区分捕食者和猎物的。本课题是建立在对海洋微型浮游动物感知和响应猎物信号的感觉机制的研究基础上的。第一个目的是确定Favella sp.对鞭毛类和桡足类捕食者的行为反应，以及这些行为反应的有效性。高速视频显微镜（250帧/秒）和粒子跟踪技术将量化Favella sp对来自捕食者和猎物的化学、机械（接触）和流体动力刺激的行为反应。第二个目标将确定对目标1中确定的捕食者的行为反应的机制基础。这将通过结合高速视频显微镜、电生理学和荧光离子敏感染料来确定嗜离子性和代谢机制如何介导信号转导和捕食者逃避行为。粒子图像测速也将用于确定Favella sp周围的流场如何在捕食者逃避行为期间被修改，以减少其流体动力学特征，从而降低其被摄入的可能性。总之，所提出的实验将扩展当前对纤毛虫-猎物行为相互作用的研究，以解决这种单细胞生物如何整合微尺度环境线索来探测和消耗适当的猎物，并逃避捕食者的摄入。

Animals sense a multitude of tactile, olfactory, visual, and aural sensory cues from predators and prey, integrate these cues, and respond with appropriate behaviors; avoidance or prey capture, respectively. Understanding how animals integrate these multiple signals to evoke complex behaviors is one of the central challenges in the biology of behavior. Single celled eukaryotes have many of the same sensory characteristics, at the cellular level, as multicellular animals and therefore provide excellent conceptual and functional analogues of sensory and behavioral traits in higher organisms. The researcher will use a marine microzooplankton ciliate, Favella sp., as a model organism to investigate sensory mechanisms that allow them to perceive and integrate cues from predators and prey in order to successfully capture prey while avoiding predation. Because these single celled organisms represent an early evolving group of eukaryotes, characterization of their sensory capabilities will provide insights into the evolution of integrated cell signaling and emergent behavioral traits in multicellular organisms. Moreover, understanding the predator-prey interactions of these microzooplankton, a group of organisms responsible for consuming ~60 % of marine primary productivity, will enable a better understanding of the role they play in supporting marine food webs and in fluxes of nutrients in surface oceans. Both of these larger ecosystem scale processes have implications for marine ecosystem services (e.g. fisheries) and for biogeochemical cycles that impact our climate. In addition to these important science questions, the proposed research will foster cross-disciplinary collaboration of the graduate student with experts in microzooplankton ecology. Professional training, science communication and career development of the researcher will be promoted with support to attend high profile scientific meetings. The award will also allow the researcher to further develop and implement teaching programs for high school students that will help attract them to science and technology subjects at college level, and motivate them to become involved in research as undergraduates. Microzooplankton alveolates (ciliates and dinoflagellates) transfer substantial amounts of energy from primary production to larger metazoan consumers. Underlying these predator-prey interactions are complex behaviors that allow them to efficiently capture preferred prey and evade predation by sensing and integrating a variety of stimuli from each. Despite the ecological importance of these behavioral interactions, no previous research has examined how microzooplankton are able to differentiate between predators and prey despite receiving similar types of sensory information from both. This proposal builds upon dissertation research investigating the sensory mechanisms that marine microzooplankton possess to sense and respond to signals from their prey. The first objective is to determine the behavioral responses of Favella sp. to dinoflagellate and copepod predators, and the effectiveness of these behavioral responses. High-speed videomicroscopy (250 fps) and particle tracking techniques will quantify the behavioral responses of Favella sp. to chemical, mechanical (contact) and hydrodynamic stimuli from predators and prey. The second objective will determine the mechanistic basis of behavioral responses to predators identified in objective 1. This will be accomplished using a combination of high-speed video microscopy, electrophysiology, and fluorescent ion-sensitive dyes to determine how ionotropic and metabotropic mechanisms mediate signal transduction and predator evasion behaviors. Particle image velocimetry will also be utilized to determine how the flow field surrounding Favella sp. may be modified during predator evasion behaviors to decrease its hydrodynamic signature and therefore the likelihood that it will be ingested. In summary, the proposed experiments will extend current research on ciliate-prey behavioral interactions to address the question of how this single celled organism can integrate microscale environmental cues to detect and consume appropriate prey, and evade ingestion by predators.