Biomechanics of Segmented Axial Musculature in Salamanders and Fishes

超过一半的脊椎动物是鱼类，但它们肌肉的三维（3D）几何形状和游泳行为之间的基本关系却知之甚少。鱼的身体肌肉被组织成短的肌纤维片段，由肌腱样胶原蛋白片隔开（在“鱼”鱼片中，片段是薄片）。在每个节段内，肌肉纤维以复杂的轨迹运行，并且节段本身折叠成锥形形状。这些肌肉复杂的3D结构使得人们很难理解它们在游泳中的功能。本研究的总体目标是了解分段肌肉组织的功能，在两个模型系统：成年人的水生蝾螈，海妖lacertina，和斑马鱼，斑马鱼的幼虫。选择这些模型物种是因为它们使用分段的身体肌肉进行游泳，但它们肌肉节段的3D几何形状比成鱼简单。将使用跨学科的方法来解决这个问题，包括数学建模，激光扫描共聚焦显微镜的3D数字成像，以及在游泳过程中使用基于声脉冲的技术sonomicrometry测量肌肉收缩（肌肉应变）。本研究的三个具体目标是：（1）建立猪肌纤维应变、纵向应变和三维节段变形之间关系的数学模型; lacertina;（2）利用超声测微仪测量了猪游泳过程中肌纤维的应变、纵向应变和肌节段的三维变形，对模型进行了检验和完善。lacertina;以及（3）使用共聚焦显微镜测量斑马鱼幼体分段肌肉组织的3D结构，并应用我们的3D模型来深入了解斑马鱼幼体肌肉节段的结构和功能之间的关系（斑马鱼幼体将在它们第一次开始自由游泳时进行研究-在它们孵化出卵后的一两天）。这项研究的结果将产生一个完整的理解的肌纤维角，肌肉段的形状，和结缔组织结构的力学游泳的影响。在未来，这些结果将被应用于鱼类物种的多样性，以了解鱼类肌肉骨骼系统的进化。

More than half of all vertebrate animals are fish, yet the fundamental relationship between the 3-dimensional (3D) geometry of their muscles and swimming behavior is poorly understood. The body muscles of fish are organized into short segments of muscle fibers, separated by sheets of tendon-like collagen (in "flaky" fish fillets, the segments are the flakes). Within each segment, muscle fibers run in complex trajectories and the segments themselves are folded into cone-like shapes. The complex, 3D structure of these muscles has made it difficult to understand how they function in swimming. The general objective of this study is to understand the function of segmented musculature in two model systems: adults of an aquatic salamander, Siren lacertina, and larvae of zebrafish, Danio rerio. These model species were chosen because they use segmented body muscles for swimming, but the 3D geometry of their muscle segments is simpler than in adult fishes. Interdisciplinary approaches to this problem will be used including mathematical modeling, 3D digital imaging with laser scanning confocal microscopy, and measurement of muscle contraction (muscle strain) during swimming with a sound-pulse based technique, sonomicrometry. The three specific aims of this study are: (1) to develop a mathematical model of the relationship between muscle fiber strain, longitudinal strain, and 3D segment deformation in S. lacertina; (2) to test and refine the model by measuring muscle fiber strain, longitudinal strain, and 3D segment deformation with sonomicrometry during swimming in S. lacertina; and (3) to use confocal microscopy to measure the 3D architecture of segmented musculature in zebrafish larvae, and apply our 3D model to gain insight into the relationship between structure and function of larval zebrafish muscle segments (larval zebrafish will be studied when they first begin to swim freely - a day or two after they hatch out of their eggs). The results of this study will yield an integrated understanding of the effects of muscle fiber angle, muscle segment shape, and connective tissue architecture on the mechanics of swimming. In the future, these results will be applied to the vast diversity of fish species, in order to understand the evolution of the musculoskeletal system in fishes.