Micro-ornamentation patterns in different areas of the epidermis in the gecko Tarentola mauritanica reflect variations in the accumulation of corneous material in Oberhautchen cells.

Abstract

Micro-ornamentations characterize the surface of scales in lepidosaurians and are summarized in four main patterns, i.e., spinulated, lamellated, lamellate-dentate, and honeycomb, although variations of these patterns are present in different species. Although geckos are known to possess a spinulated pattern derived from the Oberhautchen layer, also other pattern variations of the spinulated micro-ornamentation are present such as those indicated as dendritic ramification, corneous belts, and small bare patches. The present study mainly describes the variation of micro-ornamentations present in scales of different skin regions in the Mediterranean gecko Tarentula mauritanica using scannig and transmission electron microscopy. The study reports that the accumulation of corneous material in Oberhautchen cells is not homogenous in different areas of body scales and, when mature, this process gives rise to different sculpturing on the epidermal surface generating not only spinulae but also transitional zones leading to the other main patterns. It is hypothesized that spinulae formation derives from the vertical and lateral symmetric growth of tubercolate, non-overlapped scales of geckos. Sparse areas also result smooth or with serpentine-ridges likely revealing the beta-layer located underneath and merged with the Oberhautchen. The eco-functional role of this variable micro-ornamentation in the skin of lizards however remains largely speculative.