Jaw Muscle Architecture and Skull Form in Primates

虽然在灵长类动物中已经很好地研究了头骨形状和功能之间的关系，但颌肌纤维结构（如纤维长度和方向）重塑和适应不同进食行为和饮食的方式很少被研究，并且仍然知之甚少。 评估骨骼和肌肉系统在一起，这项研究探讨了头骨的形式和纤维结构的方式在功能上与摄食行为和饮食。 这项研究的结果将提供有关颌骨肌肉和骨质头骨如何在功能上整合以在进食过程中产生和限制运动的重要信息，并可应用于重建化石中的进食行为和饮食的研究。 这个项目开始于三种南美洲猴（Callitrichidae，灵长类）之间的比较。 这些猴子有独特的不同的进食行为，但在其他方面具有相似的饮食特征。 这两个亲缘关系密切的猕猴之间摄食行为的对比为评价纤维结构对肌肉功能的意义提供了一个理想的模型。 具体来说，普通的绒猴（Callithrix jacchus）通过广泛地打开它们的下巴（产生宽的下巴）并使用它们的前牙来凿树干或分支以刺激牙龈的流动来吃树树胶。 棉顶绢毛猴（Saguinus oedipus）和松鼠猴（Saimiri sciureus）也以树胶为食，但与绒猴不同的是，这些灵长类动物以已经被昆虫或其他机械损坏的树提取的树胶为食。 通过对这三只猴子的初步研究，通过以下两个具体目标解决了纤维结构，头骨形态和进食行为之间的关系。 首先，使用大体解剖学、显微镜和组织学技术检查浅表咬肌和颞肌的纤维结构。 这一假设是测试的树刨常见的绒猴有一个架构的安排，有利于生产广泛的下巴张开。 其次，将获得头骨的形态数据，以研究头骨结构如何在功能上和/或适应性地与不同的进食行为联系起来。 作为该项目长期目标的一部分，将收集原猴目和灵长类动物的纤维结构和颅骨测量数据，以评估纤维结构的颅骨相关性。 这些数据将用于测试骨骼代理是否可以用来准确地预测肌肉的结构参数，并评估这些参数如何随着头骨和身体大小的变化而变化。 该项目有一个重要的教育组成部分，涉及培训和支持本科生在这个项目的各个方面。 这项工作继续支持杜克大学妇女倡议，鼓励女大学生从事研究工作，并将加强三个学术机构之间的合作关系。

Although the relationship between skull form and function has been well studied in primates, the ways in which jaw muscle fiber architecture (such as fiber length and orientation) remodels and adapts to different feeding behaviors and diets have been rarely examined and remain poorly understood. Evaluating the bony and muscular systems together, this study examines the ways in which skull form and fiber architecture are functionally related to feeding behavior and diet. Results of this study will provide important information on how the jaw muscles and bony skull are functionally integrated to both produce and limit movement during feeding, and can be applied to studies reconstructing feeding behavior and diet in fossils. This project begins with a comparison among three species of South American monkey (Callitrichidae, Primates). These monkeys have uniquely different feeding behaviors, but are otherwise characterized by similar diets. The contrast in feeding behaviors between these closely-related monkeys provides an ideal model to evaluate the significance of fiber architecture for muscle function. Specifically, common marmosets (Callithrix jacchus) feed on tree gums by opening their jaws widely (producing a wide jaw gape) and applying their anterior teeth to gouge the tree trunk or branch in order to stimulate the flow of gums. Cotton-top tamarins (Saguinus oedipus) and squirrel monkeys (Saimiri sciureus) also feed on gums, but unlike marmosets, these primates feed on gums that have already been extracted by insects or other mechanical damage to the tree. Through initial study of these three monkeys, the relationship between fiber architecture, skull morphology and feeding behavior is addressed through the following two specific objectives. First, fiber architecture of the superficial masseter and temporalis muscles is examined using gross anatomic, microscopic, and histologic techniques. The hypothesis is tested that the tree-gouging common marmoset has an architectural arrangement that facilitates the production of wide jaw gapes. Second, morphological data on the skull will be obtained to examine how skull structure is functionally and/or adaptively linked to different feeding behaviors. As part of the long-range goals of this project, fiber architecture and craniometric data on prosimian and anthropoid primates will be collected to evaluate the cranial correlates of fiber architecture. These data will be used to test whether bone proxies can be employed to accurately predict architectural parameters of muscle, and to evaluate how these parameters vary with changes in skull and body size. The project has an important educational component that involves training and supporting undergraduate students in all aspects of this project. This work continues to support the Duke University Women's Initiative by encouraging undergraduate women in research and will also strengthen collaborative relationships among three academic institutions.