Locomotor rib kinematics in two species of lizards and a new hypothesis for the evolution of aspiration breathing in amniotes
Locomotor rib kinematics in two species of lizards and a new hypothesis for the evolution of aspiration breathing in amniotes
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DOI：
10.1038/s41598-020-64140-y
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发表时间：
2020-05-12
影响因子：
4.6
通讯作者：
Brainerd, Elizabeth L.
中科院分区：
文献类型：
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作者：
Cieri, Robert L.;Hatch, Samuel T.;Brainerd, Elizabeth L.
大多数蜥蜴行走和奔跑时都是四肢伸展的步态，其中部分肢体是通过中轴骨骼的横向起伏而向前推进的。肋骨和椎骨是不可或缺的，这种运动模式，但三维运动的轴向骨骼尚未报告蜥蜴运动。在这里，我们使用XROMM量化的椎骨和肋骨在缓慢的跑步机运动在三个萨凡纳草原巨蜥（Varanus explanaticus）和三个阿根廷黑色和白色泰格斯（Salvator merietus）的相对运动。为了隔离运动，我们选择了没有并发肺通气的步幅。肋骨旋转可以分解为围绕背腹轴的桶柄旋转、围绕中外侧轴的泵柄旋转和围绕头尾轴的卡尺旋转。在运动过程中，在两个物种中测量的每根肋骨基本上围绕其肋椎关节旋转（8-17度，在桶、泵和卡尺旋转之间相加）。在这两个物种的所有个体中，在同侧前肢的推进阶段，中间肋骨通过桶和泵柄运动向颅侧旋转。摆动期同侧前肢的轴向运动学与推进期的轴向运动学基本一致。虽然还需要进一步的研究来确定是什么导致了这些肋骨运动，但轴下肌肉组织的主动收缩可能至少是部分原因。单侧运动肋骨运动非常相似的双边模式用于肺通气，这表明一个新的假设，肋骨运动在运动过程中可能是一个exaptation的肋骨吸气呼吸的发展在干sparkotes。
Most lizards walk and run with a sprawling gait in which the limbs are partly advanced by lateral undulation of the axial skeleton. Ribs and vertebrae are integral to this locomotor mode, but 3D motion of the axial skeleton has not been reported for lizard locomotion. Here, we use XROMM to quantify the relative motions of the vertebrae and ribs during slow treadmill locomotion in three savannah monitor lizards (Varanus exanthematicus) and three Argentine black and white tegus (Salvator merianae). To isolate locomotion, we selected strides with no concurrent lung ventilation. Rib rotations can be decomposed into bucket-handle rotation around a dorsoventral axis, pump-handle rotation around a mediolateral axis, and caliper rotations around a craniocaudal axis. During locomotion, every rib measured in both species rotated substantially around its costovertebral joint (8-17 degrees, summed across bucket, pump and caliper rotations). In all individuals from both species, the middle ribs rotated cranially through bucket and pump-handle motion during the propulsive phase of the ipsilateral forelimb. Axial kinematics during swing phase of the ipsilateral forelimb were mirror images of the propulsive phase. Although further work is needed to establish what causes these rib motions, active contraction of the hypaxial musculature may be at least partly responsible. Unilateral locomotor rib movements are remarkably similar to the bilateral pattern used for lung ventilation, suggesting a new hypothesis that rib motion during locomotion may have been an exaptation for the evolution of costal aspiration breathing in stem amniotes.