Collaborative Research: The Evolutionary Significance of Variability in Mammalian Chewing: Influence of Dietary Specialization and Oral Afferents on Jaw and Hyolingual Movement

哺乳动物节奏性咀嚼的复杂动作受到进食器官形态以及舌头和牙齿中传递食物大小、形状和质地信息的感觉受体的影响。在饮食专家看来，解剖结构可能会限制这些运动只适合咀嚼少量食物。相比之下，多面手可能有能力做出更灵活的动作来应对更广泛的饮食。考虑到咀嚼运动适应性的这些潜在差异，口腔感觉受体输入的作用也可能在通才和专才之间有所不同。本研究的目的是确定口腔感觉信息和形态如何相互作用，以影响哺乳动物咀嚼过程中复杂的下颌和舌头运动。了解解剖学和饮食之间的联系是哺乳动物生物学和进化研究的基石，但在饮食进化的背景下，口腔感觉对咀嚼运动和协调的贡献还没有比较研究。研究结果将揭示影响咀嚼过程中感觉和运动系统进化的潜在选择压力，这种行为与哺乳动物的早期进化和辐射有关。结合该项目的科学成果，pi将为公立学校教育、公众宣传、各级科学家培训和研究基础设施的发展做出贡献。威廉姆斯实验室将与俄亥俄大学教育系、东南俄亥俄数学与科学卓越中心、WOUB公共媒体和当地公立学校教师合作，为初中和高中开发和实施关于进化、适应和功能形态学的教育模块。Gerstner实验室将在密歇根州和犹他州的当地学校、公共场所和实地研究所开展互动科学活动。这两个学院都将为本科生、研究生和博士后提供跨学科的研究培训。数据将通过公共在线数据库提供，FDA方法将通过网络可访问的综合R档案网络传播。咀嚼涉及到下巴、舌头和舌骨非常复杂、小而快速的运动。在每一次咀嚼循环中，下颚的运动使牙齿排列整齐以分解食物。舌骨支撑着舌头，维持牙齿上的食物。饮食的形态特化影响这些运动，口腔感觉受体与中枢和外周运动系统之间的相互作用也是如此。目前，我们还不知道饮食适应是否会影响动物对感觉刺激变化的运动反应范围，也不知道口腔感觉系统与不同物种的适应情况之间的关系。使用x射线运动形态重建（XROMM），该项目将确定1)饮食形态特化如何影响咀嚼运动学；2)在缺乏口腔感觉反馈的情况下，运动如何受到影响。XROMM可以连续测量下颌、舌头和舌骨的三维咀嚼运动。将对4名饮食通才和4名系统发育匹配的专家进行比较。首先通过从连续运动曲线中提取预定的运动学变量来分析数据。由于这种方法使大多数数据未被分析，因此这项工作的最终目的是在功能数据分析（FDA）的标题下开发和测试新的分析工具，并将结果与先前的分析进行比较。FDA是xrom的理想合作伙伴，因为它可以分析整个运动概况。研究结果将通过同行评议的出版物和在科学会议上的报告进行传播。

The complex movements involved in rhythmic chewing in mammals are influenced by the morphology of the feeding apparatus as well as sensory receptors in the tongue and teeth which relay information on the size, shape, and texture of foods. In dietary specialists, anatomy may limit these movements to those that are ideal for chewing a narrow range of foods. In contrast, generalists may be capable of more variable movements to deal with broader diets. Given these potential differences in the adaptability of the chewing movements, the role of input from oral sensory receptors may also differ between generalists and specialists. The goal of this study is to determine how oral sensory information and morphology interact to influence the complex jaw and tongue movements that occur during mastication in mammals. Understanding the link between anatomy and diet has been a cornerstone of studies of mammalian biology and evolution but there are no comparative studies on the contribution of oral sensation to chewing movements and coordination within the context of dietary evolution. Results will shed light on potential selective pressures influencing the evolution of sensory and motor systems involved in mastication, a behavior that is implicated in the early evolution and radiation of mammals. In conjunction with the scientific outcomes of this project, PIs will contribute to public school education, public outreach, training of scientists at all levels and the development of research infrastructure. The Williams lab will work with the Ohio University Department of Education, the South East Ohio Center for Excellence in Mathematics and Science, WOUB Public Media and local public school teachers to develop and implement educational modules on evolution, adaptation and functional morphology for middle and high schools. The Gerstner lab will conduct interactive science activities at local schools, and public venues and field institutes in Michigan and Utah. Both PIs will provide interdisciplinary research training for undergraduates, graduate students and post-doctoral associates. Data will be made available through public online databases and FDA methods will be disseminated through the web-accessible Comprehensive R Archive Network.Mastication involves very complex, small and fast movements of the jaw, tongue and hyoid. In each chewing cycle, jaw movements align the teeth to break down food. The tongue, supported by the hyoid, maintains the food on the teeth. Morphological specializations for diet influence these movements, as do interactions between oral sensory receptors and central and peripheral motor systems. Currently, we do not know whether dietary adaptations influence an animal's range of kinematic responses to changes in sensory stimuli, or how oral sensory systems relate to the adaptive profile of diverse species. Using X-ray Reconstruction of Moving Morphology (XROMM), this project will determine how 1) morphological specialization for diet impacts chewing kinematics and 2) movements are affected in the absence of oral sensory feedback. XROMM allows the continuous measurement of the 3D masticatory movements of the jaw, tongue and hyoid. Comparisons will be made between 4 dietary generalists and 4 phylogenetically-matched specialists. Data are first analyzed by extracting predetermined kinematic variables from continuous movement profiles. As this approach leaves most of the data unanalyzed, the final aim of this work is to develop and test new analytic tools under the rubric of Functional Data Analysis (FDA) and compare results to the previous analyses. FDA is an ideal partner for XROMM because it analyzes the entire movement profile. Results will be disseminated through peer reviewed publications and presentations at scientific meetings.