Breathing with floating ribs: XROMM analysis of lung ventilation in savannah monitor lizards
Breathing with floating ribs: XROMM analysis of lung ventilation in savannah monitor lizards
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DOI：
10.1242/jeb.189449
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发表时间：
2018-11-01
影响因子：
2.8
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.;Moritz, Sabine;Brainerd, Elizabeth L.
脊椎动物肺和躯干的结构和功能通过通气行为联系在一起，但这些结构和功能之间的联系知之甚少。我们使用X射线重建的运动形态（XROMM），以测量肺通气过程中的肋骨运动学在三个萨凡纳草原巨蜥（Varanus explanaticus）。所有的背侧肋骨，包括浮肋，有助于通风;幅度和运动模式显示没有检测到的头-尾梯度。真正的肋骨作为两个刚性体连接的柔性软骨，与椎肋和腹内侧干的每一个胸骨肋保持刚性和软骨之间形成一个灵活的肋内关节。肋骨旋转可分解为桶柄围绕背腹轴旋转、泵柄围绕中外侧轴旋转和卡钳围绕头尾轴运动。在两个个体中，背肋运动由大致相等的铲斗和泵旋转贡献主导，在第三个个体中由铲斗旋转主导。巨蜥在换气过程中浮肋的募集与鬣蜥的情况截然不同，鬣蜥只有前几根真正的肋骨有助于呼吸。这种差异可能与两种动物的呼吸系统结构和生活史特征有关。浮动肋骨的运动可以最大限度地通风的尾部和腹外侧定位的兼容囊腔在肺的Varanids，而限制通风的几个真正的肋骨可以最大限度地隐藏在鬣蜥。
The structures and functions of the vertebrate lung and trunk are linked through the act of ventilation, but the connections between these structures and functions are poorly understood. We used X-ray reconstruction of moving morphology (XROMM) to measure rib kinematics during lung ventilation in three savannah monitor lizards (Varanus exanthematicus). All of the dorsal ribs, including the floating ribs, contributed to ventilation; the magnitude and kinematic pattern showed no detectable cranial-to-caudal gradient. The true ribs acted as two rigid bodies connected by flexible cartilage, with the vertebral rib and ventromedial shaft of each sternal rib remaining rigid and the cartilage between them forming a flexible intracostal joint. Rib rotations can be decomposed into bucket handle rotation around a dorsoventral axis, pump handle rotation around a mediolateral axis and caliper motion around a craniocaudal axis. Dorsal rib motion was dominated by roughly equal contributions of bucket and pump rotation in two individuals and by bucket rotation in the third individual. The recruitment of floating ribs during ventilation in monitor lizards is strikingly different from the situation in iguanas, where only the first few true ribs contribute to breathing. This difference may be related to the design of the pulmonary system and life history traits in these two species. Motion of the floating ribs may maximize ventilation of the caudally and ventrolaterally positioned compliant saccular chambers in the lungs of varanids, while restriction of ventilation to a few true ribs may maximize crypsis in iguanas.