Frongia Gian N, Muzzeddu Marco, Mereu Paolo, Leoni Giovanni, Berlinguer Fiammetta, Zedda Marco, Farina Vittorio, Satta Valentina, Di Stefano Marco, Naitana Salvatore
Department of Veterinary Medicine, University of Sassari, Via Vienna 2, Sassari, Italy.
Bonassai Breeding and Wildlife Recovery Center, Regional Forest Agency FoReSTAS, Viale Merello, Cagliari, Italy.
J Morphol. 2018 Dec;279(12):1753-1763. doi: 10.1002/jmor.20893. Epub 2018 Nov 5.
Flight is an energetically costly form of transport imparting biomechanical stress that acts upon the wing bones. Previous studies have suggested that the cross-sectional and microstructural features of wing bones may be adapted to resist biomechanical loads. During flight, however, each wing bone potentially experiences a unique loading regime. To assess possible differences among wing bones, we analyzed the microstructural features of the humerus, radius, ulna, and carpometacarpus (CMC) in eight griffon vultures (Gyps fulvus). Vascular canal orientation was evaluated in the diaphysis of the wing bones. Laminarity index (LI) was significantly different in the humerus versus CMC and ulna versus CMC. Results showed a lower proportion of circular vascular canals, due to resistance to torsional loads, in CMC than in humerus and ulna. The midshaft cross-section revealed an elliptical shape in the CMC compared to the circular shape observed in the other wing bones, with a maximum second moment of inertia (I ) orientation which suggests a capacity to withstand bending loads in a dorsoventral direction. The volumetric bone mineral density in the diaphysis was statistically different in CMC compared to the other bones analyzed. Its lower mineral density may reflect an adaptation to a different type and load of stresses in CMC compared to the proximal wing bones. No significant difference was found in the relative cortical area (CA/TA) among the four elements, while the polar moment of area J (Length-standardized) revealed a higher resistance to torsional load in the humerus than in the other bones. Our results would seem to indicate that griffon wing bones are structured as an adaptation, represented by two segments that respond to force in two ways: the proximal segment is specially adapted to resist torsional loads, whereas the distal one is adapted to resist bending loads.
飞行是一种能量消耗巨大的运输方式，会给翼骨施加生物力学应力。先前的研究表明，翼骨的横截面和微观结构特征可能会适应以抵抗生物力学负荷。然而，在飞行过程中，每根翼骨可能会经历独特的负荷状态。为了评估翼骨之间可能存在的差异，我们分析了八只兀鹫（Gyps fulvus）的肱骨、桡骨、尺骨和腕掌骨（CMC）的微观结构特征。在翼骨骨干中评估血管管的方向。肱骨与CMC以及尺骨与CMC之间的层流指数（LI）存在显著差异。结果显示，由于抵抗扭转载荷，CMC中圆形血管管的比例低于肱骨和尺骨。与其他翼骨观察到的圆形相比，CMC的中轴横截面呈椭圆形，其最大惯性矩（I）方向表明其具有承受背腹方向弯曲负荷的能力。与其他分析的骨头相比，CMC骨干中的体积骨矿物质密度在统计学上存在差异。其较低的矿物质密度可能反映了与近端翼骨相比，CMC对不同类型和负荷应力的适应性。在这四个部位的相对皮质面积（CA/TA）中未发现显著差异，而面积极矩J（长度标准化）显示肱骨比其他骨头对扭转载荷的抵抗力更高。我们的结果似乎表明，兀鹫的翼骨结构是一种适应性结构，由两个部分组成，以两种方式对力作出反应：近端部分特别适应抵抗扭转载荷，而远端部分则适应抵抗弯曲负荷。
