The structure of the digital setae of lizards

TLDR

The α layer of the lizard stratum corneum is readily identifiable in the lamellae. Lamellae adhere via a surface phenomenon, with spatulas creating a large contact area that generates substantial friction. Light and electron microscopy revealed that gecko setae are long, branched structures with many small spatulas, whereas anoline lizard setae are shorter, simpler, and have larger terminal spatulas; both groups evolved their setae independently from epidermal spines, and the β layer of the lamellae remains poorly defined.

Abstract

Abstract Light and electron microscope studies of the digital lamellar setae of geckos and anoline lizards demonstrate that the free ends of the setae consist of flattened spatulas of less than 1 μ in width. The anoline setae are simple structures usually less than 30 μ in length and with a single terminal spatula to each seta. In contrast the setae of geckos are complex structures of about 100 μ in length, with numerous branchings, and having many spatulas per seta. The spatulas of Gekko and Aristelliger were smaller (0.2‐0.4 μ in width) than the spatulas of Anolis (0.8 μ in width). The electron microscope studies indicate that the scales of lizards appear to be covered with small epidermal spines (1.5 μ long). The setae of anoles and geckos are considered to have evolved independently from these more primitive epidermal spines. It is further suggested that the mechanism that allows the lamellae to adhere to the substratum is a surface phenomenon. The spatulas provide a large surface that is in contact with the substratum and thus produces a large total frictional force. The α layer of the lizard stratum corneum can be readily identified in the lamellae. However, the structure of the β layer is not easily interpreted and there is evidence of a fibrous layer between the Oberhautchen and the α layer in the skin of the outer lamellar surface.