Scaling of claw sharpness: mechanical constraints reduce attachment performance in larger insects.
J Exp Biol
The Company of Biologists
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Pattrick, J. G., Labonte, D., & Federle, W. (2018). Scaling of claw sharpness: mechanical constraints reduce attachment performance in larger insects.. J Exp Biol, 221 (Pt 24) https://doi.org/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 (Nauphoeta cinerea, Gromphadorhina portentosa, Atta cephalotes and Carausius morosus) 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 A. cephalotes and G. portentosa (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.
Extremities, Animals, Cockroaches, Ants, Body Size, Biomechanical Phenomena, Insecta
JGP was funded by a Biotechnology and Biological Sciences Research Council PhD Studentship under grant BB/J014540/1.
Biotechnology and Biological Sciences Research Council (BB/I008667/1)
Biotechnology and Biological Sciences Research Council (BB/E004156/1)
External DOI: https://doi.org/10.1242/jeb.188391
This record's URL: https://www.repository.cam.ac.uk/handle/1810/286391