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

哺乳动物的咀嚼或咀嚼器官为研究已灭绝和现存哺乳动物的进化、行为、饮食和生态提供了一扇窗口。之前的研究已经深入到这些领域，为哺乳动物咀嚼形式提供了适应性、功能性和生物力学的解释。本研究将以羊驼（Lama pacos）和山羊（Capra hircus）为模型，采用综合方法来了解偶蹄动物反刍或反刍时进食装置的形式与功能之间的关系。咀嚼和其他进食行为的动态将通过肌电图记录颚肌的行为，应变测量技术来了解下颌骨和面部骨骼如何受到外力的负荷，以及视频记录下颌肌肉收缩产生的下颌运动。这些数据将与口腔行为数据以及来自解剖、组织学分析和影像学研究的比较解剖学和形态学数据相结合。本研究的一个主要组成部分将集中在摄食动力学和咀嚼器官的解剖结构如何随着摄食行为和消化生理的正常个体发生变化而变化。由于包括兔子和猪在内的非反刍哺乳动物也有类似的数据，因此将对不同物种进行比较，以突出与消化策略相关的咀嚼器官发展中的可能适应和限制。本研究中收集的数据也将用于解决关于颌骨形态与生长之间关系的假设，在其常规功能环境的背景下。在羊驼和山羊中，这种功能环境包括与反刍相关的高度重复的咀嚼行为，大约在三到四个月大的时候开始，远远早于成年咀嚼形态的形成。有趣的是，羊驼及其近亲在成年颌骨形态上不同于山羊和所有其他反刍偶蹄动物。在前者中，下颌骨两半之间的关节在个体发育早期骨化，而在后者中，该关节在整个生命中保持通畅和活动。这些差异被认为与成人咀嚼行为相关的下颌骨负荷环境的差异有关。因此，本研究将检验关于重复力学因素在下颌骨结构和生长差异中的作用的假设。这项研究的更广泛的影响包括对PI（一名少数族裔女性科学家开始她的研究生生涯）的额外培训，以及在俄亥俄（OU）和俄亥俄州立大学（OSU）两所大学为本科生和研究生提供跨学科教育和培训机会。这些学生将在实验和比较功能形态学和生物力学方面接受方法论和概念方法的培训。学生还将通过在生物力学、进化和功能形态学以及古生物学领域的专业期刊上发表论文和在专业会议上发表论文来参与传播本研究的结果。最后，该研究项目将通过为体内和体外应变分析提供基础设施和专业知识，并通过这笔拨款加强俄亥俄州立大学和俄亥俄州立大学之间的学术和研究关系，扩大俄亥俄大学功能形态学和生物力学培训的范围。

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.