Why do tree frogs and geckos not fall off walls?
Keywords:
Adhesion, Anura, Scan electron microscopy, Squamae, ToesAbstract
Some lizards, tree frogs and insects have the ability to move across vertical surfaces. A comparative study showed that the system of biological adhesion converges in two main models: hairy and smooth. These mechanisms include superficial interactions, such as the secretion of fluids and molecular interactions. With the aim of linking this ability to a biological explanation, toe specimens from lizards [Hemidactylus mabouia (Moreau de Jonnès, 1818) Reptilia, Gekkonidae] and tree frogs [Dendropsophus minutus (Peters, 1872) Anura, Hylidae] were analyzed and
photographed using scan electron microscopy. The lizard’s toe is composed of a coating of scales, claws and structures that look like a “pad”. These “pads” are
composed of filamentous and branch-like structures at the extremities. The filaments allow an enlargement of the contact area between the toe and the substrate, providing greater adhesion and balance. The scales that surround the “pads” are different, displaying a central orifice that we assume to be glandular openings. The tree frog’s toe is composed of hexagonal, columnar cells, with a clearly defined space between each one. Its digits have glands which secrete a viscous substance used for adhesion. Despite the morphological differences, the toes of lizards and tree frogs display similar functions, namely adhesion and protection, since they allow these animals to move in places with difficult access, even for their predators.
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