Microscopic studies on the structure of microornamentation and adhesive setae in normal and regenerating tail scales of some geckos.

The present review summarizes recent information on the formation and fine structure of epidermal microornamentation and adhesive setae in scale pads of the tail in some arboreal geckos. The study utilizes transmission and scanning electron microscopy, in conjunction with immunolabeling, to detect the main proteins of the microornamentation, known as Corneous Beta Proteins. These are special small proteins with a central region containing beta-sheets that form most of the corneous material of scales and pads. These proteins are packed into long cords that form short spinulae or longer setae. In tail scales, the spinulae feature different shapes but possess a limited size, 0.5-2.0 µm. In sparse areas located toward the distal part of the tail, some scales form adhesive pads, and their microornamentation grows longer, forming setae of 10-30 µm in length in the species studied herein. This process gives rise to stiff but flexible bristles that arboreal geckos use for adhesion on vertical or inverted substrates or tree branches. During tail regeneration, some scales also regenerate the adhesive setae and give rise to new adhesive pads. Caudal setae are formed by a process similar to that observed during the formation of digital setae. This derives from the interaction of a specific epidermal layer (clear) with another layer (Oberhäutchen), which are formed in the scale pads. Setae vary in length, diameter, or terminal arborization, and they resemble those of the digits, albeit shorter. The presence of caudal adhesive pads reinforces the prehensibility and maneuverability of these arboreal lizards in their environment.