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，但颌骨肌肉纤维结构(如纤维长度和方向)如何重塑和适应不同的摄食行为和饮食的方式很少被研究，而且仍然知之甚少。这项研究同时评估了骨骼和肌肉系统，研究了头骨形状和纤维结构在功能上与进食行为和饮食有关的方式。这项研究的结果将为颌肌和骨头骨如何在摄食过程中产生和限制运动提供重要的信息，并可用于研究重建化石的摄食行为和饮食。该项目首先对南美三种猴子(长颈猴、灵长类)进行比较。这些猴子有独特的不同摄食行为，但在其他方面具有相似的饮食特征。这些近亲猴子在进食行为上的差异为评估纤维结构对肌肉功能的重要性提供了一个理想的模型。具体地说，普通的绒猴(Callithrix Jacchus)以树胶为食，它们的下巴张开(产生一个宽大的下巴)，并用它们的前牙挖出树干或树枝，以刺激树胶的流动。棉冠金丝猴和松鼠猴也以口香糖为食，但与绒猴不同的是，这些灵长类动物的口香糖已经被昆虫提取或对树木造成其他机械损伤。通过对这三只猴子的初步研究，通过以下两个具体目标来研究纤维结构、头骨形态和摄食行为之间的关系。首先，用大体解剖、显微镜和组织学技术研究咬肌浅层和颞肌的纤维构筑。这一假设得到了检验，即挖树常见的绒猴具有一种有利于产生宽大下巴口子的结构安排。其次，将获得头骨的形态数据，以检查头骨结构如何在功能和/或适应性上与不同的摄食行为相联系。作为该项目长期目标的一部分，将收集原猴和类人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。这些数据将被用来测试骨骼替代物是否可以用来准确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，包括在该项目的各个方面对本科生进行培训和支持。这项工作继续支持杜克大学妇女倡议，鼓励女本科生参与研究，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.