Krings Markus, Nyakatura John A, Boumans Mark L L M, Fischer Martin S, Wagner Hermann
Department of Animal Physiology and Zoology, RWTH Aachen University, Aachen, Germany.
AG Morphologie und Formengeschichte, Bild Wissen Gestaltung. Ein interdisziplinäres Labor, Humboldt-University Berlin, Berlin, Germany.
J Anat. 2017 Jul;231(1):12-22. doi: 10.1111/joa.12616. Epub 2017 Apr 27.
Owls are known for their outstanding neck mobility: these birds can rotate their heads more than 270°. The anatomical basis of this extraordinary neck rotation ability is not well understood. We used X-ray fluoroscopy of living owls as well as forced neck rotations in dead specimens and computer tomographic (CT) reconstructions to study how the individual cervical joints contribute to head rotation in barn owls (Tyto furcata pratincola). The X-ray data showed the natural posture of the neck, and the reconstructions of the CT-scans provided the shapes of the individual vertebrae. Joint mobility was analyzed in a spherical coordinate system. The rotational capability was described as rotation about the yaw and roll axes. The analyses suggest a functional division of the cervical spine into several regions. Most importantly, an upper region shows high rolling and yawing capabilities. The mobility of the lower, more horizontally oriented joints of the cervical spine is restricted mainly to the roll axis. These rolling movements lead to lateral bending, effectively resulting in a side shift of the head compared with the trunk during large rotations. The joints in the middle of the cervical spine proved to contribute less to head rotation. The analysis of joint mobility demonstrated how owls might maximize horizontal head rotation by a specific and variable combination of yawing and rolling in functionally diverse regions of the neck.
这些鸟类能够将头部旋转超过270°。这种非凡的颈部旋转能力的解剖学基础尚未得到很好的理解。我们对活猫头鹰进行了X射线荧光透视检查，并对死标本进行了强制颈部旋转以及计算机断层扫描（CT）重建，以研究单个颈椎关节如何在仓鸮（Tyto furcata pratincola）中对头部旋转做出贡献。X射线数据显示了颈部的自然姿势，CT扫描重建提供了单个椎骨的形状。在球坐标系中分析关节活动度。旋转能力被描述为绕偏航轴和横滚轴的旋转。分析表明颈椎可分为几个功能区域。最重要的是，上部区域显示出较高的横滚和偏航能力。颈椎下部更水平方向的关节活动度主要限于横滚轴。这些横滚运动导致侧向弯曲，在大角度旋转时实际上会使头部相对于躯干产生侧向偏移。颈椎中部的关节对头部旋转的贡献较小。关节活动度分析表明，猫头鹰可能通过在颈部功能不同的区域进行特定且可变的偏航和横滚组合，来最大限度地实现头部水平旋转。
