Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK.
Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.
J Exp Biol. 2018 Dec 12;221(Pt 24):jeb188391. doi: 10.1242/jeb.188391.
Claws are the most widespread attachment devices in animals, but comparatively little is known about the mechanics of claw attachment. A key morphological parameter in determining attachment ability is claw sharpness; however, there is a conflict between sharpness and fracture resistance. Sharper claws can interlock on more surfaces but are more likely to break. Body size interacts with this conflict such that larger animals should have much blunter claws and consequently poorer attachment ability than smaller animals. This expected size-induced reduction in attachment performance has not previously been investigated, and it is unclear how animals deal with this effect, and whether it indeed exists. We explored the scaling of claw sharpness with body size using four insect species (, , and ) each covering a large size range. The scaling of claw sharpness varied significantly between species, suggesting that they face different pressures regarding claw function. Attachment forces were measured for and (which had different scaling of claw sharpness) on several rough surfaces using a centrifuge setup. As expected, attachment performance was poorer in larger animals. Firstly, larger animals were more likely to slip, although this effect depended on the scaling of claw sharpness. Secondly, when they gripped, they attached with smaller forces relative to their weight. This size-induced reduction in attachment performance has significant implications for the attachment ability of larger animals on rough surfaces.
爪子是动物中最广泛的附着装置，但关于爪子附着的力学原理却知之甚少。决定附着能力的一个关键形态参数是爪子的锋利度；然而，锋利度和抗断裂性之间存在冲突。更锋利的爪子可以在更多的表面上互锁，但更容易断裂。体型与这种冲突相互作用，使得较大的动物应该具有更钝的爪子，因此附着能力比较小的动物差。以前没有研究过这种预期的体型诱导的附着性能下降，也不清楚动物如何应对这种影响，以及它是否确实存在。我们使用 4 种昆虫物种（、、和），每种物种都涵盖了很大的体型范围，探索了爪子锋利度与体型的比例关系。爪子锋利度的比例关系在物种之间存在显著差异，这表明它们面临着不同的爪子功能压力。我们使用离心装置在几种粗糙表面上测量了 和 的附着力（它们的爪子锋利度比例关系不同）。正如预期的那样，较大的动物附着性能较差。首先，较大的动物更容易滑动，尽管这种效应取决于爪子锋利度的比例关系。其次，当它们抓住物体时，相对于它们的体重，它们施加的附着力较小。这种体型诱导的附着性能下降对较大动物在粗糙表面上的附着能力有重大影响。
