Federle W, Barnes W J P, Baumgartner W, Drechsler P, Smith J M
Division of Environmental and Evolutionary Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
J R Soc Interface. 2006 Oct 22;3(10):689-97. doi: 10.1098/rsif.2006.0135.
Tree frogs are remarkable for their capacity to cling to smooth surfaces using large toe pads. The adhesive skin of tree frog toe pads is characterized by peg-studded hexagonal cells separated by deep channels into which mucus glands open. The pads are completely wetted with watery mucus, which led previous authors to suggest that attachment is solely due to capillary and viscous forces generated by the fluid-filled joint between the pad and the substrate. Here, we present evidence from single-toe force measurements, laser tweezer microrheometry of pad mucus and interference reflection microscopy of the contact zone in Litoria caerulea, that tree frog attachment forces are significantly enhanced by close contacts and boundary friction between the pad epidermis and the substrate, facilitated by the highly regular pad microstructure.
树蛙能够利用大脚趾垫附着在光滑表面上，这一点颇为引人注目。树蛙脚趾垫具有黏性的皮肤，其特征是布满钉状突起的六边形细胞，这些细胞由深沟隔开，黏液腺开口于这些深沟中。脚趾垫完全被水性黏液浸湿，这使得之前的研究者认为，附着仅仅是由于垫与基质之间充满液体的间隙所产生的毛细作用力和黏性力。在此，我们通过对蓝树蛙（Litoria caerulea）进行单趾力测量、对垫黏液进行激光镊子微流变学测量以及对接触区域进行干涉反射显微镜观察，得出证据表明，高度规则的垫微观结构促进了垫表皮与基质之间的紧密接触和边界摩擦，从而显著增强了树蛙的附着力。
