Comparative Investigations of the Sandfish’s β-Keratin (Reptilia: Scincidae: <i>Scincus scincus</i>). Part 1: Surface and Molecular Examinations

Abstract

The Sandfish (Scincidae: Scincus Scincus) Is a Lizard Capable of Moving through Desert Sand in a Swimming-Like Fashion. the Epidermis of this Lizard Shows a High Resistance against Abrasion Together with a Low Friction to Sand as an Adaption to a Subterranean Life below the Desert’s Surface, Outperforming even Steel. the Low Friction Is Mainly Caused by Chemical Composition of the Scales, which Consist of Glycosylated β-Keratins. in this Study, the Friction, the Micro-Structure, the Glycosylation of the β-Keratin Proteins and β-Keratin Coding DNA of the Sandfish in Comparison to other Reptilian Species Was Investigated, Mainly with the Closely Related Berber Skink (Scincidae: Eumeces Schneideri) and another Sand Swimming Species, the Not Closer Related Shovel-Snouted Lizard (Lacertidae: Meroles Anchietae). Glycosylated β-Keratins of the Sandfish, Visualized with Different Lectins Resulted in O-Linked Glycans through PNA Employed as Carbohydrate Marker. Furthermore, the Glycosylation of β-Keratins in Various Squamatean Species Was Investigated and All Species Tested Were Found Positive; however, it Seems Like both Sand Swimming Species Examined Have a much Stronger Glycosylation of their β-Keratins. in Order to Prove this Finding through a Genetic Foundation, DNA of a β-Keratin Coding Gene of the Sandfish Was Sequenced and Compared with a Homologue Gene of Eumeces Schneideri. by Comparison of the Protein Sequence, a Higher Abundance of O-Glycosylation Sites Was Found in the Sandfish (enabled through the Amino Acids Serine and Threonine), Giving Molecular Support for a Higher Glycosylation of the β-Keratins in this Species.

Review: mapping epidermal beta-protein distribution in the lizard Anolis carolinensis shows a specific localization for the formation of scales, pads, and claws

“…Therefore, a direct comparison between the avian sequences and the reptilian sequences was not possible. When the gene structure and primary sequences of reptilian betakeratins became known for the first time in lizards and snakes (Dalla Valle et al 2005, and later in the remaining nonavian sauropsids (Dalla Valle et al , 2009aValle et al , b, 2010Hallahan et al 2008;Ye et al 2010;Staudt et al 2012), and the colocalization with alpha-keratins was shown (Alibardi 2012(Alibardi , 2013a(Alibardi -e, 2015, the new interpretation outlined above on the process of cornification in sauropsids was strengthened. This interpretation indicates that the so-called beta-keratins represent the more abundant class of nonkeratin proteins of sauropsids that associate to keratins as "keratin-associated beta-proteins" (KABPs) or as "corneous beta-proteins" (CBPs).…”

“…1S A and C). Other studies on the sandfish lizard have evidenced that some betaproteins can also be glycosylated, a process that has been put in relation to the formation of a beta-layer adapted to lower the friction with the ground where this species is adapted to dig, borrow, and move (Staudt et al 2012). …”

Immunocytochemistry indicates that glycine‐rich beta‐proteins are present in the beta‐layer, while cysteine‐rich beta‐proteins are present in beta‐ and alpha‐layers of snake epidermis

“…A recent study on beta‐proteins of the sandfish lizard, a species that is adapted to dig and move in the sand, has suggested that beta‐keratin can be glycosylated, further extending possible roles for these small structural proteins (Staudt et al . ,b). The latter study indicates that glycosylation of beta‐keratins occurs prevalently in the sandfish lizard although, in other species not adapted to the sand environment, beta‐keratins also appear to contain a lower amount of glycosylation.…”

“…; Staudt et al . ). These studies have indicated that sauropsid beta‐keratins are the analogous proteins indicated in mammals as KAPs, and they are now indicated as ‘keratin‐associated beta‐proteins’ (KAbetaPs) or simply beta‐proteins.…”

Bio-inspired 3D funnel structures made by grayscale electron-beam patterning and selective topography equilibration

“…Possible inspiration comes from snake-skins having surface features enabling low friction in a preferred moving direction [2]. For example sand-swimming reptiles, like the sandfish, have micro-structures on there skin that allow them, in combination with the biochemical composition of the structures, to move in sand with very low friction [3]. Shark denticles are also developed by nature to reduce the fluid-drag in water [4].…”