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

哺乳动物在有节奏的咀嚼中涉及的复杂运动受到摄食装置的形态以及舌头和牙齿中的感官感受器的影响，感官感受器传递关于食物的大小、形状和质地的信息。在饮食专家中，解剖学可能会将这些运动限制在那些适合咀嚼少数食物的运动。相比之下，多面手可能会有更多变化的运动来处理更广泛的饮食。鉴于咀嚼运动在适应性方面的这些潜在差异，来自口腔感官感受器的输入的作用在通才和专家之间也可能不同。这项研究的目的是确定口腔感觉信息和形态如何相互作用，影响哺乳动物咀嚼过程中发生的复杂的下巴和舌头运动。了解解剖学和饮食之间的联系一直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，还没有关于口腔感觉对咀嚼运动和协调的贡献的比较研究。结果将阐明潜在的选择压力，影响与咀嚼有关的感觉和运动系统的进化，这一行为与哺乳动物的早期进化和辐射有关。结合这一项目的科学成果，个人投资促进公立学校教育、公众宣传、各级科学家的培训和研究基础设施的发展。威廉姆斯实验室将与俄亥俄大学教育部、东南部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、公共场所和野外研究所开展互动科学活动。这两个私人投资机构将为本科生、研究生和博士后助理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的方法将通过网络可访问的全面R档案网络传播。咀嚼涉及非常复杂、微小和快速的下巴、舌头和舌骨的运动。在每个咀嚼周期中，下巴的运动会对齐牙齿来分解食物。舌头由舌骨支撑，维持牙齿上的食物。饮食的形态专门化影响这些运动，就像口腔感官受体与中枢和外周运动系统之间的相互作用一样。目前，我们不知道饮食适应是否会影响动物对感觉刺激变化的运动学反应范围，也不知道口腔感觉系统如何与不同物种的适应特征有关。利用X射线运动形态重建(XROMM)，该项目将确定1)饮食的形态特化如何影响咀嚼运动学，以及2)在缺乏口腔感觉反馈的情况下，运动是如何受到影响的。XROMM可以连续测量下颌、舌头和舌骨的3D咀嚼运动。将在4名饮食通才和4名系统发育匹配的专家之间进行比较。首先通过从连续的运动轮廓中提取预定的运动学变量来分析数据。由于这种方法没有分析大部分数据，这项工作的最终目标是在功能数据分析(FDA)的框架下开发和测试新的分析工具，并将结果与以前的分析进行比较。FDA是XROMM的理想合作伙伴，因为它分析了整个运动情况。结果将通过同行评议的出版物和在科学会议上的介绍来传播。

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.