Du Trina Y, Standen Emily M
Department of Biology, University of Ottawa, Gendron Hall, 30 Marie Curie, Ottawa, ON, Canada K1N 6N5
Department of Biology, University of Ottawa, Gendron Hall, 30 Marie Curie, Ottawa, ON, Canada K1N 6N5.
J Exp Biol. 2020 Jun 8;223(Pt 11):jeb217554. doi: 10.1242/jeb.217554.
The ability of bones to sense and respond to mechanical loading is a central feature of vertebrate skeletons. However, the functional demands imposed on terrestrial and aquatic animals differ vastly. The pectoral girdle of the basal actinopterygian fish was previously shown to exhibit plasticity following terrestrial acclimation, but the pectoral fin itself has yet to be examined. We investigated skeletal plasticity in the pectoral fins of after exposure to terrestrial loading. Juvenile fish were divided into three groups: a control group was kept under aquatic conditions without intervention, an exercised group was also kept in water but received daily exercise on land, and a terrestrial group was kept in a chronic semi-terrestrial condition. After 5 weeks, the pectoral fins were cleared and stained with Alcian Blue and Alizarin Red to visualize cartilage and bone, allowing measurements of bone length, bone width, ossification and curvature to be taken for the endochondral radial bones. fin bones responded most strongly to chronic loading in the terrestrial condition. Fish that were reared in a terrestrial environment had significantly longer bones compared with those of aquatic controls, wider propterygia and metapterygia, and more ossified metapterygia and medial radials, and they showed changes in propterygial curvature. Exercised fish also had longer and more ossified medial radials compared with those of controls. fin bones exhibit plasticity in response to novel terrestrial loading. Such plasticity could be relevant for transitions between water and land on evolutionary scales, but key differences between fish and tetrapod bone make direct comparisons challenging.
骨骼感知并响应机械负荷的能力是脊椎动物骨骼的一个核心特征。然而，施加在陆生动物和水生动物身上的功能需求差异巨大。先前的研究表明，基底辐鳍鱼类的肩带在陆地驯化后会表现出可塑性，但胸鳍本身尚未得到研究。我们研究了暴露于陆地负荷后胸鳍的骨骼可塑性。幼鱼被分为三组：对照组在无干预的水生条件下饲养，运动组也饲养在水中，但每天在陆地上进行运动，陆地组则饲养在长期半陆地条件下。5周后，将胸鳍清理并用阿尔新蓝和茜素红染色以观察软骨和骨骼，从而可以测量软骨内桡骨的骨长度、骨宽度、骨化程度和曲率。胸鳍骨骼对陆地条件下的长期负荷反应最为强烈。与水生对照组相比，在陆地环境中饲养的鱼的骨骼明显更长，前鳍基骨和中鳍基骨更宽，中鳍基骨和内侧桡骨的骨化程度更高，并且它们的前鳍基骨曲率也发生了变化。与对照组相比，运动组的鱼的内侧桡骨也更长且骨化程度更高。胸鳍骨骼在响应新的陆地负荷时表现出可塑性。这种可塑性在进化尺度上可能与水陆过渡有关，但鱼类和四足动物骨骼之间的关键差异使得直接比较具有挑战性。
