Patel Biren A, Organ Jason M, Jashashvili Tea, Bui Stephanie H, Dunsworth Holly M
Department of Integrative Anatomical Sciences, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
Human and Evolutionary Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA.
J Anat. 2018 Jan;232(1):39-53. doi: 10.1111/joa.12720. Epub 2017 Nov 3.
Life history variables including the timing of locomotor independence, along with changes in preferred locomotor behaviors and substrate use during development, influence how primates use their feet throughout ontogeny. Changes in foot function during development, in particular the nature of how the hallux is used in grasping, can lead to different structural changes in foot bones. To test this hypothesis, metatarsal midshaft rigidity [estimated from the polar second moment of area (J) scaled to bone length] and cross-sectional shape (calculated from the ratio of maximum and minimum second moments of area, I /I ) were examined in a cross-sectional ontogenetic sample of rhesus macaques (Macaca mulatta; n = 73) and common chimpanzees (Pan troglodytes; n = 79). Results show the hallucal metatarsal (Mt1) is relatively more rigid (with higher scaled J-values) in younger chimpanzees and macaques, with significant decreases in relative rigidity in both taxa until the age of achieving locomotor independence. Within each age group, Mt1 rigidity is always significantly higher in chimpanzees than macaques. When compared with the lateral metatarsals (Mt2-5), the Mt1 is relatively more rigid in both taxa and across all ages; however, this difference is significantly greater in chimpanzees. Length and J scale with negative allometry in all metatarsals and in both species (except the Mt2 of chimpanzees, which scales with positive allometry). Only in macaques does Mt1 midshaft shape significantly change across ontogeny, with older individuals having more elliptical cross-sections. Different patterns of development in metatarsal diaphyseal rigidity and shape likely reflect the different ways in which the foot, and in particular the hallux, functions across ontogeny in apes and monkeys.
生活史变量，包括运动独立的时间，以及发育过程中偏好的运动行为和底物使用的变化，会影响灵长类动物在个体发育过程中如何使用它们的脚。发育过程中足部功能的变化，特别是大脚趾在抓握时的使用方式，会导致足部骨骼结构的不同变化。为了验证这一假设，在恒河猴（猕猴属；n = 73）和普通黑猩猩（黑猩猩属；n = 79）的一个横断面个体发育样本中，研究了跖骨中轴刚性[根据面积极惯性矩（J）按骨长度缩放估算]和横截面形状（根据面积最大和最小惯性矩之比I/I计算）。结果显示，在幼年黑猩猩和猕猴中，拇趾跖骨（Mt1）相对更刚性（具有更高的缩放J值），在两个分类群中，直到实现运动独立之前，相对刚性都显著降低。在每个年龄组中，黑猩猩的Mt1刚性总是显著高于猕猴。与外侧跖骨（Mt2 - 5）相比，Mt1在两个分类群和所有年龄组中都相对更刚性；然而，这种差异在黑猩猩中显著更大。所有跖骨以及两个物种的长度和J值都呈负异速生长（除了黑猩猩的Mt2呈正异速生长）。只有在猕猴中，Mt1中轴形状在个体发育过程中显著变化，年长个体的横截面更椭圆。跖骨干刚性和形状的不同发育模式可能反映了猿类和猴类在个体发育过程中足部，特别是大脚趾的不同功能方式。
