Craniofacial Biomechanics in Camelids: In vivo and Comparative Studies in Form and Function

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Craniofacial biomechanics in camelids: in vivo and comparative studies in form and functionSusan H. WilliamsOhio University College of Osteopathic MedicineThe mammalian masticatory or chewing apparatus provides a window into the evolution, behavior, diet and ecology of extinct and living mammals. Previous research has tapped into each of these realms to offer adaptive, functional and biomechanical explanations of mammalian masticatory form. In this study, an integrative approach will be used to understand the relationship between form and function of the feeding apparatus in ruminating, or cud-chewing, artiodactyls using alpacas (Lama pacos) and goats (Capra hircus) as models. The dynamics of mastication and other feeding behaviors will be explored using electromyography to record the behavior of jaw muscles, strain gauge techniques to understand how the mandible and facial skeleton are loaded by external forces, and video recordings to document jaw movements produced by contraction of the jaw muscles. These data will be integrated with data on oral behaviors and with comparative anatomical and morphological data derived from dissections, histological analyses and imaging studies.A major component of this study will focus on how feeding dynamics and the anatomy of the masticatory apparatus change in concert with normal ontogenetic changes in feeding behavior and digestive physiology. As similar data are available for non-ruminating mammals, including rabbits and pigs, comparisons will be made across species to highlight possible adaptations and constraints in the development of the masticatory apparatus associated with digestive strategies. Data collected in this study will also be used to address hypotheses regarding the relationship between jaw form and growth in the context of its routine functional environment. In alpacas and goats, this functional environment consists of highly repetitive chewing behaviors associated with rumination beginning around three to four months of age, well before adult masticatory morphology is attained. Interestingly, alpacas and their close relatives differ from goats and all other ruminating artiodactyls in adult jaw morphology. In the former, the joint between the two halves of the mandible ossifies early during ontogeny whereas in the latter this joint remains patent and mobile throughout life. These differences are thought to be related to differences in loading environment of the mandible associated with adult masticatory behaviors. Thus, this study will test hypotheses regarding the role of repetitive mechanical factors in relation to differences in structure and growth of the mandible.The broader impacts of this study include additional training for the PI, a minority female scientist at the start of her post-graduate career, and interdisciplinary educational and training opportunities for undergraduate and graduate students at two universities, Ohio (OU) and Ohio State University (OSU). These students will receive training in methodological and conceptual approaches in experimental and comparative functional morphology and biomechanics. Students will also participate in disseminating the results of this study by presenting at professional meetings and collaborating on publications for professional journals in the fields of biomechanics, evolutionary and functional morphology, and paleontology. Finally, this research program will broaden the scope of functional morphology and biomechanics training at Ohio University by contributing infrastructure and expertise for in vivo and in vitro strain analysis and by enhancing academic and research relationships between OU and OSU through this grant.