Reptilian Skin and Its Special Histological Structures

Abstract

Reptilian skin is covered with scales forming armor that makes it watertight and enables reptiles to live on land in contrast to amphibians. An important part of the skin is the horny epidermis, with thick stratum corneum in which waxes are arranged in membrane-like layers. In lizards and snakes, the whole skin is covered in overlapping epidermal scales and in turtles and crocodiles in dermal scutes. The cornified part of the epidermis is strengthened by β-keratin and sometimes α-keratin. In crocodiles and many turtles, the outer scale surface consists of β-keratin and the hinge region containing α-keratin. In lizards and snakes, both keratins form continuous layers with the α-keratin below the β-keratin. Some reptiles have developed a sensitive mechanosensory system in the skin. The colors of reptile skin are produced by melanocytes and three types of chromatophores: melanophores, xanthophores, and iridophores. The color patterns may be fixed or the chromatophores may provide rapid color change. Skin from different species of reptiles, turtles (red-eared slider (Trachemys scripta elegans)), snakes (Emerald tree boa (Corallus caninus) and Burmese python (Python bivittatus)), Cuvier's dwarf caiman (Paleosuchus palpebrosus), lizards (Leopard Gecko (Eublepharis macularius)), and Green iguana (Iguana iguana), were examined with histology techniques and compared.

Morphological study of the integument and corporal skeletal muscles of two psammophilous members of Scincidae (Scincus scincus and Eumeces schneideri)

“…The melanocytes are located just under the stratum germinativum on the upper side of the dermis ( stratum laxum ). The dermis of both species presents the common characteristics of the dermis of squamates (Bellairs, 1969; Rutland, Cigler, & Kubale, 2019), being mainly composed of fibrous collagen. The deep dermis is separated from the underlying body wall muscles by a thin hypodermis, consisting of adipocytes.…”

The integument of pelagic crocodylomorphs (Thalattosuchia: Metriorhynchidae)

“…The overlapping, epidermally-defined scales of Lepidosauria (squamate lizards and snakes [including mosasaurs], as well as the tuatara and its fossil kin, see Maderson, 1968) differ fundamentally from the non-overlapping scales of crocodiles, turtles, and bird limbs. Scales in these latter taxa are covered with rigid β-keratin and interlinked by α-keratin hinges (Alibardi et al, 2009;Rutland et al, 2019) and are inferred to represent the more ancient condition. Whereas lepidosaurs perform singular ecdysis, these other reptiles shed their epidermis in fragmented flakes (Spearman and Riley, 1969).…”

The sensory peripheral nervous system in the tail of a cephalochordate studied by serial blockface scanning electron microscopy

“…In reptiles (Rutland, Cigler, & Kubale, 2019) and mammals (Kanitakis, 2001), the distinction between the superficial (papillary) dermis and the deeper (reticular) dermis is less conspicuous than in other vertebrates, and neither zone includes a dense orthogonally organized collagenous layer. In both the papillary and reticular dermis, the collagen fibrils tend to be bundled together into stouter fibers loosely organized into a mesh, and the peripheral nerves ramify through the rather spacious interstices in this mesh (Krause, 1921;Reinisch & Tschachler, 2012).…”