Sustaita Diego, Gloumakov Yuri, Tsang Leah R, Dollar Aaron M
Department of Biological Sciences, California State University, San Marcos, San Marcos, CA, USA.
Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, USA.
PeerJ. 2019 Feb 5;7:e6243. doi: 10.7717/peerj.6243. eCollection 2019.
Ospreys are renowned for their fishing abilities, which have largely been attributed to their specialized talon morphology and semi-zygodactyly-the ability to rotate the fourth toe to accompany the first toe in opposition of toes II and III. Anecdotal observations indicate that zygodactyly in Ospreys is associated with prey capture, although to our knowledge this has not been rigorously tested. As a first pass toward understanding the functional significance of semi-zygodactyly in Ospreys, we scoured the internet for images of Osprey feet in a variety of circumstances. From these we cross-tabulated the number of times each of three toe configurations (anisodactylous, zygodactylous, and an intermediate condition between these) was associated with different grasping scenarios (e.g., grasping prey or perched), contact conditions (e.g., fish, other objects, or substrate), object sizes (relative to foot size), and grasping behaviors (e.g., using one or both feet). Our analysis confirms an association between zygodactyly and grasping behavior; the odds that an osprey exhibited zygodactyly while grasping objects in flight were 5.7 times greater than whilst perched. Furthermore, the odds of zygodactyly during single-foot grasps were 4.1 times greater when pictured grasping fish compared to other objects. These results suggest a functional association between predatory behavior and zygodactyly and has implications for the selective role of predatory performance in the evolution of zygodactyly more generally.
鹗以其捕鱼能力而闻名，这在很大程度上归因于它们特殊的爪形态和半对趾形态——即第四趾能够旋转，与第一趾相对，与第二和第三趾相对。轶事观察表明，鹗的对趾形态与猎物捕获有关，尽管据我们所知，这尚未经过严格测试。作为理解鹗半对趾形态功能意义的第一步，我们在互联网上搜索了鹗在各种情况下脚部的图像。从这些图像中，我们交叉列出了三种趾构型（不等趾型、对趾型以及介于两者之间的中间状态）与不同抓握场景（例如抓握猎物或栖息）、接触条件（例如鱼、其他物体或基质）、物体大小（相对于脚的大小）以及抓握行为（例如用一只脚或两只脚）的出现次数。我们的分析证实了对趾形态与抓握行为之间的关联；鹗在飞行中抓握物体时表现出对趾形态的几率比栖息时大5.7倍。此外，与抓握其他物体相比，当鹗抓握鱼时，单脚抓握时出现对趾形态的几率大4.1倍。这些结果表明捕食行为与对趾形态之间存在功能关联，并且更普遍地对捕食性能在对趾形态进化中的选择作用具有启示意义。
