Dorso-ventral skin of flowered racer snake (coluber flourulentus, perreti schatti, 1988): Histological, Keratin immunohistochemical, and ultrastructural characterization

Our study, using SEM and histology, aims to characterize the dorsal and ventral skin of Coluber flourulentus, providing new insights into their Keratin immunohistochemical features. The SEM findings revealed overlapping smooth scales on both surfaces, with minor scale morphology variations; the dorsal scales were finger-shaped with a pointed apex, while the ventral scales were flattened with tooth-like edges. Scales on both surfaces reveal two large, spherical-shaped lenticular sensory organs at their apex, dome-shaped receptors/sensilla on the outer surface, and dome-shaped sensilla with dendrites, a transverse cleft, and various pits and pores. Histologically, the micro-ornamentations on the inner-scale surfaces of both surfaces had similar structures with smooth, spiny scales and two layers. The epidermis layer had several layers, including the basal stratum germinativum, α-keratin, the Mesos layer, the β-layer, and the covered Oberhautchen layer. Skin pigmentation varied between both surfaces: the dorsal dermal layer contains melanophores and iridophores, and the ventral dermal layer contains only dark black melanophores under the epidermal layer. Histochemical collagen fiber observations revealed blue-colored fibers in the dermis of dorsal and ventral surfaces, sparse underneath the basement membrane, and visible around pigment cells and muscle bundles. A dark brown reaction was observed in the epidermal cells of both dorsal and ventral surfaces, with high cytokeratin immunolabeling on the ventral surface and moderate cytokeratin immunoreaction on the dorsal surface. In conclusion, scales were crucial for controlling movements and responding to vibrational stimuli from object movements, including those of potential prey or predators.