Jaw Muscle Architecture and Skull Form in Primates

尽管在灵长类动物中，头骨形状和功能之间的关系已经得到了很好的研究，但颌骨肌纤维结构（如纤维长度和方向）的重塑和适应不同摄食行为和饮食的方式却很少得到研究，而且仍然知之甚少。通过对骨骼和肌肉系统的综合评估，本研究考察了颅骨形态和纤维结构在功能上与摄食行为和饮食的关系。该研究结果将为研究颌骨肌肉和颅骨如何在功能上整合以产生和限制进食过程中的运动提供重要信息，并可用于研究化石中摄食行为和饮食的重建。本项目首先比较了南美洲三种猴（猴科，灵长类）。这些猴子有独特的不同的进食行为，但其他方面的特征是相似的饮食。这些亲缘关系密切的猴子在摄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。具体来说，普通狨猴（Callithrix jacchus）以树胶为食，它们张开大嘴巴（形成一个大的颌口），用前牙凿开树干或树枝，以刺激树胶的流动。棉顶绢毛猴（Saguinus oedipus）和松鼠猴（Saimiri sciureus）也以树胶为食，但与狨猴不同的是，这些灵长类动物的树胶已经被昆虫或其他机械损伤提取出来了。通过对这三只猴子的初步研究，通过以下两个具体目标来解决纤维结构、头骨形态和摄食行为之间的关系。首先，使用大体解剖、显微和组织学技术检查浅咬肌和颞肌的纤维结构。这一假设得到了验证，即挖树的普通狨猴有一种结构安排，有助于产生宽阔的颌口。其次，将获得头骨的形态学数据，以研究头骨结构如何在功能上和/或适应上与不同的摄食行为联系起来。作为该项目的长期目标的一部分，将收集原猿和类人猿灵长类动物的纤维结构和颅骨测量数据，以评估纤维结构与颅骨的相关性。这些数据将用于测试骨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颅骨和体型的变化而变化。该项目有一个重要的教育组成部分，包括在项目的各个方面对本科生进行培训和支持。这项工作将继续支持杜克大学妇女倡议，鼓励本科生参与研究，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.