Byron Craig D, Herrel Anthony, Pauwels Elin, Muynck Amelie De, Patel Biren A
Department of Biology, Mercer University, Macon, Georgia.
Departement d'Ecologie et de Gestion de la Biodiversite, CNRS/MNHN, Paris, France.
J Morphol. 2015 Jul;276(7):759-65. doi: 10.1002/jmor.20376. Epub 2015 Mar 11.
Mice raised in experimental habitats containing an artificial network of narrow "arboreal" supports frequently use hallucal grasps during locomotion. Therefore, mice in these experiments can be used to model a rudimentary form of arboreal locomotion in an animal without other morphological specializations for using a fine branch niche. This model would prove useful to better understand the origins of arboreal behaviors in mammals like primates. In this study, we examined if locomotion on these substrates influences the mid-diaphyseal cross-sectional geometry of mouse metatarsals. Thirty CD-1/ICR mice were raised in either arboreal (composed of elevated narrow branches of varying orientation) or terrestrial (flat ramps and walkways that are stratified) habitats from weaning (21 days) to adulthood (≥4 months). After experiments, the hallucal metatarsal (Mt1) and third metatarsal (Mt3) for each individual were isolated and micro-computed tomography (micro-CT) scans were obtained to calculate mid-shaft cross-sectional area and polar section modulus. Arboreal mice had Mt1s that were significantly more robust. Mt3 cross sections were not significantly different between groups. The arboreal group also exhibited a significantly greater Mt1/Mt3 ratio for both robusticity measures. We conclude that the hallucal metatarsal exhibits significant phenotypic plasticity in response to arboreal treatment due to habitual locomotion that uses a rudimentary hallucal grasp. Our results support the hypothesis that early adaptive stages of fine branch arboreality should be accompanied by a slightly more robust hallux associated with the biomechanical demands of this niche.
在包含狭窄“树栖”支撑物人工网络的实验栖息地中饲养的小鼠，在运动过程中经常使用拇趾抓握。因此，这些实验中的小鼠可用于模拟一种动物树栖运动的基本形式，而该动物没有其他用于利用精细树枝生态位的形态学特化。这个模型将有助于更好地理解灵长类等哺乳动物树栖行为的起源。在本研究中，我们研究了在这些基质上的运动是否会影响小鼠跖骨骨干中部的横截面几何形状。30只CD-1/ICR小鼠从断奶（21天）到成年（≥4个月），饲养在树栖（由不同方向的高架狭窄树枝组成）或陆地（分层的平坦斜坡和走道）栖息地中。实验结束后，分离出每只小鼠的拇趾跖骨（Mt1）和第三跖骨（Mt3），并进行微型计算机断层扫描（micro-CT）以计算骨干中部横截面积和极惯性矩。树栖小鼠的Mt1明显更粗壮。两组之间的Mt3横截面没有显著差异。在两种粗壮度测量中树栖组的Mt1/Mt3比值也显著更高。我们得出结论，由于习惯性运动使用基本的拇趾抓握，拇趾跖骨对树栖处理表现出显著的表型可塑性。我们的结果支持这样的假设，即精细树枝树栖生活的早期适应阶段应伴随着与该生态位生物力学需求相关的略粗壮的拇趾。
