Adductor Muscle Function and Fiber Type in Macaca and Papio

了解灵长类动物在咀嚼时使用下颚的方式对体质人类学非常重要，因为咀嚼对头骨的形状有重大影响。 对头骨形状影响的了解有助于人类学家解释已灭绝灵长类动物的进化历史和行为，并了解现存灵长类动物的解剖和功能之间的关系。 本研究的目的是确定咀嚼肌纤维类型的变化是否与咀嚼过程中的肌肉活动有关。 本研究将（1）使用组织化学和电泳记录成年雄性和雌性猕猴和狒狒咀嚼肌中I型（慢）和II型（快）纤维的比例和横截面积，（2）确定纤维类型是否存在性二态性，（3）确定这些动物咀嚼期间纤维类型的比例如何与肌电活动相关。 快纤维的比例与咀嚼过程中快速产生大咬合力直接相关的假设将被检验。 这项研究很重要，因为人们对咀嚼过程中肌纤维类型和活动之间的关系知之甚少，它将提供有关头骨结构-功能联系的新信息。 此外，该数据将解决关于咀嚼肌纤维类型是否存在性别二型性的争议。 如果存在性二型，这些数据将为理解性二型的功能含义提供基线。

Understanding the ways in which primates use their jaws during chewing is of great importance to physical anthropology because chewing has a major influence on the form of the skull. Knowledge of the influences on skull form helps anthropologists interpret the evolutionary history and behavior of extinct primates and understand the relationship between anatomy and function in living primates. The goal of this study is to determine whether, for the chewing muscles, variation in fiber type is linked to muscle activity during chewing. This research will (1) document the proportion and cross-sectional area of the Type I (slow) and Type II (fast) fibers in the chewing muscles of adult male and female macaques and baboons using histochemistry and electrophoresis, (2) determine whether sexual dimorphism in fiber type is present, and (3) determine how the proportions of fiber types are correlated with electromyographic activity during chewing in these animals. The hypothesis that the proportion of fast fibers is directly related to the rapid production of large bite forces during chewing will be tested. This research is important because little is known about the relation between muscle fiber type and activity during chewing, and it will provide new information about structure-function links in the skull. Furthermore, the data will resolve the controversy over whether there is sexual dimorphism in the fiber type of the chewing muscles. If sexual dimorphism is present, the data will provide a baseline for understanding the functional implications of sexual dimorphism.