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First evidence of unicellular glands in the general epidermis of terrestrial reptiles

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Abstract

The general integument of reptiles is traditionally defined as being dry, but we report here the discovery of unicellular mucoid glands (UCMG) in the dorsal skin of lizards of the genus Phelsuma (Gekkonidae). To this end, the skin of these lizards and of some others for comparison was studied by scanning electron microscopy and transmission electron microscopy. These photographs showed that the development and function of the UCMGs are related to the skin’s sloughing cycle. The UCMGs differentiate at scattered locations from Oberhäutchen cells of the inner (new) epidermal generation, above the differentiating β-keratin layer. While the inner generation matures, the UCMG increases in size; unlike the surrounding Oberhäutchen cells, it does not develop the spinules that characterize gecko skin. When, upon sloughing, the inner generation becomes the new outer generation, and the Oberhäutchen forms the skin surface, the UCMGs, several per scale, dot the surface as mucus-inflated “blebs” projecting from the surrounding spinulate Oberhäutchen, each nesting in a shallow pit of the underlying β-keratin. On the surface, the UCMGs rupture and the mucus appears to dissipate in cords, flowing over the tips of the spinules, and incorporating minute foreign bodies. It is concluded that, due to the low wettability of the spinulate surface (derived from the spacing of the spinules), the cords brush off easily, with the mucus functioning as a cleaning agent.

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Acknowledgements

This discovery is an offshoot of YLW’s fieldwork on Hawaii, and he thanks Bill Mautz, University of Hawaii at Hilo, for his hospitality and support and Ken Smith and Nurit Werner for their participation in the field. We are deeply indebted to the following persons living in Germany for providing us with samples used in this study: Ulrike Anders (Hamburg), Michael Franken (Münster), Gerhard Hallmann, (Dortmund), Sandra Jager (Berlin), Frank Jäger (Dietzenbach), Hartmut Lipp (Braunschweig), and Gebhardt Roland (Bayreuth). Furthermore, we thank Mrs. I. Schroeder and Mrs. S. Seidel for skillful technical assistance and, last but not least, Nurit Sharet for Fig. 4.

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Hiller, U., Werner, Y.L. First evidence of unicellular glands in the general epidermis of terrestrial reptiles. Naturwissenschaften 95, 193–202 (2008). https://doi.org/10.1007/s00114-007-0311-6

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