Chemical Defenses in a Toxic Dinoflagellate: Mechanisms and Constraints

智力优势：亚历山大鞭毛属的物种遍布全球，一些物种，因为它们的毒素生产，被假设为关键物种。亚历山大菌产生的化合物似乎针对不同的消费者。神经毒素如PST的目标是后生动物食草动物。在实验室的初步实验中，研究人员还证实了活性氧的存在，至少以原生食草动物为目标。这些化合物降低了食草动物的适应性，并且，至少在PST的情况下，已被证明对食草动物有深远的进化影响。食草动物的适应反过来又会影响亚历山大菌的种群动态。一个普遍的假设是，浮游植物中有毒化合物的产生代表了一种适应性防御。然而，明确的实验证据支持这一假设是稀缺的。这个项目将是对化学防御假说的严格实验检验。该项目的研究人员将调查一系列实验上可证伪的假设，包括受到亚历山大菌挑战的后生动物和原生食草动物。该项目将提供新的理解和洞察，决定食草动物诱导毒素产生的因素，化学防御程度与放牧易感性之间的关系，以及亚历山大菌化学防御机制的成本和权衡。验证或反驳化学防御假说对于有毒藻华的形成、控制和持续以及化学介导的捕食者-猎物相互作用的概念模型至关重要。更广泛的影响：目前迫切需要提高公众对公共资助的科学和世界海洋的认识。为了满足这一需求，研究人员将与专业教育工作者合作，将研究结果转化为符合国家科学标准的课程材料。他们将通过他们的网站“捕食者和有毒猎物”向中学教育工作者提供这项研究和相关研究的结果，教育工作者可以在那里找到可以纳入高中课程的材料。调查人员还将在专门针对中学教育工作者的讲习班和专业教育工作者的会议上介绍网站内容。首席研究员和他的团队将继续通过网站、外行文章和“水怪”电视连续剧向外行观众推广研究结果。本项目将培养1名博士生和1 - 2名本科生。此外，拟议的工作将吸引研究生和本科生在几个领域的研究，从生理学到生态和进化过程。在此过程中，这些学生将有效地研究导致适应性的新兴特性，并将这些观点应用于海洋学。

Intellectual merit: Species of the dinoflagellate genus Alexandrium occur around the globe, and some species, because of their toxin production, have been hypothesized to be keystone species. Alexandrium produces chemical compounds that appear to target different consumers. Neurotoxins such as PST target metazoan grazers. In preliminary experiments in their laboratory, the investigators also verified the presence of reactive oxygen species that target, at a minimum, protistan grazers. Such compounds reduce grazer fitness, and, at least in the case of PST, have been shown to have profound evolutionary effects on grazers. Grazer adaptation, in turn, can affect Alexandrium population dynamics. A common assumption is that production of toxic compounds in phytoplankton represents an adaptive defense. However, unequivocal experimental evidence in support of this hypothesis is scarce. This project will be a rigorous experimental test of the chemical defense hypothesis. The project's investigators will invwestigate a series of experimentally falsifiable hypotheses with both metazoan and protistan grazers challenged with Alexandrium. This project will provide novel understanding of, and insight into, the factors that determine grazer-induced toxin production, the relationship between degree of chemical defense and susceptibility to grazing, and the costs and tradeoffs of the purported mechanisms of chemical defense in Alexandrium. Verification or refutation of the chemical defense hypothesis is essential to conceptual models of the formation, control and persistence of toxic algal blooms, and chemically-mediated predator-prey interactions. Broader impact: There is an immediate and urgent need to improve the public's awareness of publicly funded science and the world's oceans. To help fill this need, the investigators will work with professional educators to translate results from this study into prepared curricular materials that meet national science standards. They will make the results of this and related studies available to secondary educators through their website "Predators and toxic prey," where educators will find materials that can be incorporated into high school curricula. The investigators also will present the website contents at workshops specifically targeted at secondary school educators, and at meetings of professional educators. The lead investigator and his team will continue to extend the results of research to lay audiences, as well, through the website, lay articles and the "Aquakids" TV series. This project will train one Ph.D. student and one or two undergraduates. In addition, the proposed work will engage graduate and undergraduate students in several areas of research from physiology to ecological and evolutionary processes. In the process, these students will effectively be studying the emergent properties that lead to adaptability and apply such perspectives to oceanography.