Skin structure of the slow worm lizard Anguis fragilis (Anguidae, Sauria, Reptilia) with emphasis on the epidermal micro-ornamentation in relation to the animal movements

Abstract

Skin structure of the slow worm lizard Anguis fragilis (Anguidae, Sauria, Reptilia) with emphasis on the epidermal micro-ornamentation in relation to the animal movements (Acta Zoologica, Stockholm). The structure of the skin and superficial micro-ornamentation in the slow worm Anguis fragilis, a limbless lizard with a fossorial activity, was examined using histology, immunofluorescence, scanning and transmission electron microscopy. The scales, with a triangular to trapezoidal shape, are very overlapped and interlocked to form a smooth surface and are reinforced by osteoderms. The epidermis shows a thin Oberhautchen layer merged with a thicker beta-layer that contains corneous beta-proteins. The SEM survey detects a smooth surface made of tile-like patterned Oberhautchen cells with irregular perimeters that form an interlocking surface. Disk-like sensory organs of 15–20 μm diameter are observed only on the head scales, the first to sense the environment and contact the ground. Numerous Oberhautchen denticles, namely corneous thorns of about 0.2–0.3 μm, adorn the caudally directed perimeter of Oberhautchen cells in the ventral scales of the trunk and tail. This microstructure may determine gripping and increased friction with the substrate during the lateral undulating and forward movements of the slow worm. TEM observations reveal sparse short serrated protrusions of Oberhautchen cells that are largely merged with the underlying beta-cells. Altogether, the scale surface of the slow worm efficiently suites this limbless lizard to its environment and lifestyle.