Phylogenetic structural scaling of the appendicular skeleton: relationship with loading regime and locomotor behaviour

缩放研究考察了结构如何随着动物体型的增加而变化。大多数先前的标度研究都用长度和中轴直径来表征骨的形状，并用动物的质量来量化骨的负荷。在这项跨学科研究中，我们将整合工程分析，包括图像分析，详细力学，运动学测量和统计形状建模，以确定骨骼如何在一系列物种和大小之间变化。我们将调查来自以下分支的5个物种：两足鸟类、哺乳动物食肉动物（猫、狗、狼、狮子）、大足科动物（袋鼠、小袋鼠）、牛偶蹄动物（有蹄类哺乳动物）和卡塔林灵长类动物（陆生猴子）。我们将使用类似于3D x射线的计算机断层扫描图像来确定影响骨骼机械性能及其承受载荷能力的骨骼结构特征。我们将使用多摄像机运动分析系统和测力板来测量每只动物的运动行为。这将使我们能够确定关节角度、地面接触力、肢体位置和步幅特征，这些都是运动行为和骨负荷机制的组成部分。使用一系列统计技术，我们将确定骨骼结构和运动行为之间的关系。一些不规则形状的骨骼，如肩胛骨和骨盆，其形状很难量化。与长骨不同，长骨的结构测量，如横截面积，很容易确定，而不规则骨骼没有明显的尺寸可测量。统计形状建模通过创建骨骼的虚拟模型并将其形状与平均骨骼进行比较来克服这一困难。该技术考虑了所有的可变性和高光，形状发生最大的可变性。这些统计形状模型可以用来预测关节中相应骨骼的形状。这项技术对古生物学家来说非常有用，因为古生物学家经常有不完整的骨骼，必须预测缺失骨骼的形状。它还将展示关节骨骼的形状是如何紧密地通过它们相互关联的负荷机制联系在一起的。骨头是由叫做骨小梁的小针状体组成的。骨小梁的大小和方向受骨负荷的影响。很少有研究考察不同物种间小梁结构的差异。我们将获得每个物种的小梁骨样本，并使用分辨率高达5微米的微型ct对其进行成像。我们将获得小梁结构的标准三维测量，如小梁的厚度和方向。小梁结构测量将与运动参数相关联，以确定载荷、大小和运动行为如何影响骨微观结构。我们的研究也将把肌肉骨骼缩放的研究带入一个全新的、非常综合的方向。我们设计了一项研究：(1)在多个结构水平上检查阑尾骨骼中的所有骨骼，(2)使用广泛的分类群和大小，(3)应用机械方法来理解骨骼结构和运动行为，(4)采用严格的统计技术来确定结构和功能之间的关系。

Scaling studies examine how structures change in response to increasing animal size. Most previous scaling studies have characterized bone shape with length and midshaft diameter and quantified loading on the bone with the mass of the animal. In this interdisciplinary study we will integrate engineering analyses, including image analysis, detailed mechanics, kinematics measurements and statistical shape modelling to determine how bones change across a range of species and sizes. We will investigate 5 species from each of the following clades: bipedal birds, mammalian carnivores (cats, dogs, wolves, lions), Macropodoidea (kangaroos, wallabies), bovine artiodactyls (hoofed mammals), and catarrhine primates (terrestrial monkeys). We will use computer tomography images, similar to 3D x-rays, to determine the structural characteristics of the bone that affect the bone's mechanical properties and its ability to withstand load. We will measure the locomotor behaviour of each animal using a multi-camera motion analysis system and force plates. This will allow us to determine joint angles, ground contact forces, limb positions, and stride characteristics that are integral components of locomotor behaviour and hence bone loading regimes. Using a range of statistical techniques we will determine the relationship between bone structure and the locomotor behaviour. The shapes of some irregularly-shaped bones, such as the scapula and pelvis, are difficult to quantify. Unlike long bones where structural measures, such as cross-sectional area, are simple to determine, irregular bones have no obvious dimensions to measure. Statistical shape modelling overcomes this difficulty by creating a virtual model of the bone and comparing its shape to an average bone. The technique considers all variability and highlights were the most variability in shape occurs. These statistical shape models can be used to predict the shape of the corresponding bone in a joint. This technique would prove extremely useful for palaeontologists who often have incomplete skeletons and must predict the shapes of missing bones. It will also show how closely the shapes of articulating bones are linked via their interrelated loading regimes. Bone is made up of tiny spicules called trabeculae. The size and orientation of the trabeculae are influenced by the loading on the bone. Few studies have examined how the trabecular structure varies across species. We will obtain trabecular bone samples from each species and image them using microCT, which has a resolution up to 5 micrometers. We will obtain standard 3D measures of the trabecular structure, such as trabecular thickness and orientation. Trabecular structural measures will be correlated with locomotor parameters in order to determine how the loading, size, and locomotor behaviour influences bone micro-structure. Our study will also take research on musculoskeletal scaling into a new, extremely integrative direction. We have designed a study that (1) examines all bones in the appendicular skeleton at multiple structural levels, (2) uses a wide range of taxa and sizes, (3) applies a mechanistic approach to understanding bone structure and locomotor behaviour, and (4) employs rigorous statistical techniques to determine relationships between structure and function.