Doctoral Dissertation Research: The Biomechanical Evolution of Echinoderm Locomotion

脆星是海星的近亲，它们的运动方式与所有其他移动动物不同。它们的手臂由数百个活动部件组成。因此，脆性恒星可以向任何方向快速移动。他们还可以很容易地调整自己的运动方法，以应对肢体的损伤和丧失。这个项目将确定表征这种独特的运动模式演变的机械步骤。与活着的脆星相比，化石脆星显示出更多的手臂结构多样性，这使得对它们的运动模式的解释成为一个挑战。这些研究人员将使用3D成像来描述脆性恒星化石的解剖结构，并基于生物力学建模来推断它们的运动能力。这是第一个使用最先进的3D成像和生物力学建模技术来研究非脊椎动物运动机制的项目。这项研究的一个更广泛的影响是，它为系统研究整个动物界的不同运动策略及其在机械工程中的应用打开了大门。这些动物采用的独特运动策略也可能有助于改进机器人设计。建立脆星运动模型的第一步是使用3Dx射线成像技术数字化它们的内部骨架。然后使用计算机程序来制作骨骼模型并重建关节处的运动。利用高分辨率3D成像识别化石中的肌肉附着位置；骨骼的微观结构揭示了肌肉插入的位置。第二个程序用于将肌肉重建合并到骨骼模型中。可以计算出每个手臂部分和整个手臂施加的力，以揭示脆性恒星化石是否可以像它们的现代亲戚一样运动，或者使用一种更类似于活着的海星的不同策略。这些模型将允许确定导致活着的脆性恒星独特运动形式的机械步骤，并展示它们的运动模式是如何演变的。

Brittle stars, close relatives of sea stars, move in a different manner from all other mobile animals. Their arms consist of hundreds of moving parts. As a result, brittle stars can travel rapidly in any direction. They also easily adapt their method of locomotion in response to limb damage and loss. This project will identify the mechanical steps that characterize the evolution of this unique pattern of locomotion. Fossil brittle stars show much greater diversity of arm structure than living brittle stars, making interpretation of their mode of locomotion a challenge. These researchers will characterize the anatomy of fossil brittle stars using 3D imaging and infer their movement capabilities based on biomechanical modeling. This is the first project to employ state-of-the-art 3D imaging and biomechanical modeling techniques to study the mechanics of movement in any non-vertebrate animal. A broader impact of this research is that it opens the door for the systematic investigation of diverse movement strategies across the animal kingdom and their application to mechanical engineering. The unique movement strategy employed by these animals may also help improve robot design. The first step in modeling brittle star movement is to digitize their internal skeleton using 3D x-ray imaging. A computer program is then used to make a skeletal model and to reconstruct movement at the articulations. Muscle attachment sites are identified in the fossils using high-resolution 3D imaging; the microstructure of the skeleton reveals where muscles insert. A second program is used to incorporate the muscle reconstructions into the skeletal models. The force applied by each arm segment and by the entire arm can be calculated to reveal whether fossil brittle stars could move like their modern relatives, or used a different strategy more similar, for example, to that in living sea stars. These models will allow the mechanical steps leading to the unique form of movement in living brittle stars to be determined, and show how their mode of locomotion evolved.