Finite Element Analyses of the Mammalian Skull: The Impact of Biting Behavior

哺乳动物的咬人方式和进食的生物力学伊丽莎白·r·杜蒙（PI），伊恩·r·格罗斯（Co-PI）马萨诸塞大学阿默斯分校哺乳动物的进化史在很大程度上是一部关于开发越来越广泛的食物资源的故事。最早的哺乳动物以昆虫为食，而现代哺乳动物的饮食范围从昆虫到水果、树叶、肉类和浮游生物。这种饮食的多样性反映在头骨的形状上——这是哺乳动物用来咬和咀嚼食物的主要“工具”。然而，重要的是，驱动这种多样性进化的潜在机制尚不清楚。本研究探讨了咬咬过程中产生的力与哺乳动物头骨的解剖结构之间的生物力学联系的重要性，哺乳动物头骨可以安全、最佳地承受和分散这些力。此外，本研究探讨了这种关系在颅骨形状多样性进化中的作用。以前对哺乳动物喂养的分析有两种方法，每种方法都有其固有的局限性。广泛的比较研究记录了头骨形状和饮食之间的相关性，但缺乏测试相关性背后的因果机制。另一方面，详细的实验研究记录了骨骼和肌肉在进食过程中的行为，但实验条件往往与自然条件相距甚远。这项研究将是第一个将野外收集的咬行为和咬合力数据与实验室进行的生物力学实验相结合的研究。第一个目的是研究不同的咬伤方式如何对颅骨施加载荷以及这些载荷如何分散。通过比较物种内不同咬伤方式所施加的负荷机制，将确定常规咬伤行为与形态之间的因果关系。第二个目标是解决关于哺乳动物进食的另外两个未解决的问题：头骨形状在多大程度上受到其他感觉系统（在这种情况下是视觉）的限制，以及面部骨骼相对于进食过程中产生的力的强度。这些问题的答案也许可以解释为什么一些哺乳动物谱系的头骨形状比其他谱系的更多样化。最初，将测量咬咬产生的力，并在现场记录哺乳动物的摄食行为。接下来，这些行为的机械含义将在实验室中使用有限元（FE）建模和分析进行研究，这是一种基于物理的数值技术，被工程师广泛用于评估物理系统的机械行为。有限元分析（FEA）为形式-功能关系提供了一个真正新颖的视角，但大多数生物学家还无法获得。目标是通过实现两个特定的方法学目标，使有限元分析更容易获得：1)确定哺乳动物头骨的有限元模型可以简化的程度，并仍然产生足够准确的结果；2)开发有效地将ct扫描转换为三维有限元模型的协议。这些结果将通过同行评审的科学出版物、报告和研讨会传达给生物界。功能解剖学家和机械工程师之间的合作为培养研究生和本科生提供了一个极好的机会，让他们接触到生物力学、比较解剖学和机械工程方面的跨学科合作研究。研究生研究助理将进行自己的原创研究，并帮助pi指导4-6个本科生研究项目。这些项目将作为生物学和/或工程学研究生学习的跳板。

Biting Style and the Biomechanics of Feeding in MammalsElizabeth R. Dumont (PI), Ian R. Grosse (Co-PI)University of Massachusetts, AmherstThe evolutionary history of mammals is largely a story about exploiting an ever broader array of food resources. While the first mammals were insect-eaters, modern mammals specialize in diets ranging from insects to fruits, foliage, meat, and plankton. This diversity in diet is reflected in the shape of the skull - the primary 'tool' that mammals use to bite and chew food. Importantly, however, the underlying mechanism driving the evolution of this diversity is unknown. This study explores the importance of the biomechanical link between the forces generated during biting and the anatomy of mammal skulls that safely and optimally bear and disperse these forces. Further, this study investigates the role of this relationship in the evolution of diversity in skull shape.Previous analyses of mammalian feeding have taken one of two approaches, each of which has inherent limitations. Broad comparative studies document correlations between skull shape and diet, but fall short of testing the causal mechanisms underlying the correlations. On the other hand, detailed experimental studies document how bones and muscles behave during feeding, but the experimental conditions are often far from natural. This study will be the first to combine data on biting behavior and bite force gathered in the field with biomechanical experiments carried out in the laboratory.The first aim is to investigate how different biting styles apply loads to the skull and how those loads are dispersed. Causal links between routine biting behaviors and morphology will be identified by comparing the loading regimes imposed by different biting styles within species. The second aim is to address two other unresolved issues regarding feeding in mammals: the extent to which skull shape is limited by other sensory systems (in this case, vision), and the strength of the facial skeleton relative to forces generated during feeding. Answers to these issues may explain why some lineages of mammals exhibit a wider variety of skull shapes than do others. Initially, the forces generated by biting will be measured and the feeding behavior of mammals will be documented in the field. Next, the mechanical implications of these behaviors will be investigated in the laboratory using finite element (FE) modeling and analysis, a physics-based numerical technique widely used by engineers to assess the mechanical behavior of physical systems. FE analysis (FEA) provides a truly novel perspective on form-function relationships, but is not yet accessible to most biologists. An objective is to make FEA more accessible by accomplishing two specific methodological aims: 1) determine the extent to which FE models of mammal skulls can be simplified and still yield sufficiently accurate results, and 2) develop protocols for efficiently translating CT-scans into three dimensional FE models. These results will be communicated to the biology community through peer-reviewed scientific publications, presentations, and workshops. This collaboration between a functional anatomist and a mechanical engineer offers an excellent opportunity to train graduate students and to expose undergraduates to collaborative, interdisciplinary research in biomechanics, comparative anatomy, and mechanical engineering. Graduate Research Assistants will conduct their own original research, and help the PIs to mentor 4-6 undergraduate research projects. These projects will serve as a springboard to graduate studies in biology and/or engineering.