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.
