Pamfilie Alexandra M, Garner Austin M, Russell Anthony P, Dhinojwala Ali, Niewiarowski Peter H
Department of Biology, The University of Akron, Akron OH 44325-3908, USA.
Integrated Bioscience Program, The University of Akron, Akron OH 44325-3908, USA; Department of Biology, The University of Akron, Akron OH 44325-3908, USA.
Zoology (Jena). 2023 Apr;157:126078. doi: 10.1016/j.zool.2023.126078. Epub 2023 Feb 20.
Claws are a common anatomical feature among limbed amniotes and contribute to a variety of functions including prey capture, locomotion, and attachment. Previous studies of both avian and non-avian reptiles have found correlations between habitat use and claw morphology, suggesting that variation in claw shape permits effective functioning in different microhabitats. How, or if, claw morphology influences attachment performance, particularly in isolation from the rest of the digit, has received little attention. To examine the effects of claw shape on frictional interactions, we isolated the claws of preserved specimens of Cuban knight anoles (Anolis equestris), quantified variation in claw morphology via geometric morphometrics, and measured friction on four different substrates that varied in surface roughness. We found that multiple aspects of claw shape influence frictional interactions, but only on substrates for which asperities are large enough to permit mechanical interlocking with the claw. On such substrates, the diameter of the claw's tip is the most important predictor of friction, with narrower claw tips inducing greater frictional interactions than wider ones. We also found that claw curvature, length, and depth influence friction, but that these relationships depend on the substrate's surface roughness. Our findings suggest that although claw shape plays a critical role in the effective clinging ability of lizards, its relative importance is dependent upon the substrate. Description of mechanical function, as well as ecological function, is critical for a holistic understanding of claw shape variation.
爪子是有肢羊膜动物共有的解剖特征，有助于实现多种功能，包括捕食、运动和附着。先前对鸟类和非鸟类爬行动物的研究发现，栖息地利用与爪子形态之间存在关联，这表明爪子形状的差异有助于在不同的微生境中有效发挥功能。爪子形态如何影响附着性能，尤其是在与手指其他部分分离的情况下，目前鲜受关注。为了研究爪子形状对摩擦相互作用的影响，我们分离了古巴骑士安乐蜥（Anolis equestris）保存标本的爪子，通过几何形态测量法量化爪子形态的变化，并在四种表面粗糙度不同的底物上测量摩擦力。我们发现，爪子形状的多个方面会影响摩擦相互作用，但仅在粗糙程度大到足以与爪子产生机械互锁的底物上如此。在这类底物上，爪子尖端的直径是摩擦力最重要的预测指标，较窄的爪子尖端比较宽的爪子尖端产生的摩擦相互作用更大。我们还发现，爪子的曲率、长度和深度会影响摩擦力，但这些关系取决于底物的表面粗糙度。我们的研究结果表明，尽管爪子形状在蜥蜴的有效抓握能力中起着关键作用，但其相对重要性取决于底物。对机械功能以及生态功能的描述，对于全面理解爪子形状的变化至关重要。
