Novel Insights Into the Ultrastructural and Immunofluorescence Characteristics of Limb Skin in the Red-Eared Slider Turtle (Trachemys scripta elegans).

Abstract

The red-eared slider turtle, a species facing environmental challenges and habitat loss, exhibits a complex skin architecture that is crucial for its adaptation and survival. Our study aims to provide a comprehensive characterization of the turtle's skin structure and to elucidate the distribution and localization of its various cellular components, with a focus on understanding the skin's role in adaptation and ecological interactions. To achieve these goals, we employed light microscopy, transmission electron microscopy (TEM), and comprehensive immunofluorescence using 10 specific antibodies. The forelimb skin displays large- and moderate-sized scales with variations in color, including dark, yellow, and gray hues, likely contributing to camouflage and protection. The skin consists of corneous material, the epidermis, the dermis, and the hypodermis. The stratum basalis, stratum spinosum, and peri-corneous layer constitute the three distinct layers of the epidermis. There are four distinct types of chromatophores, including melanocytes located in the epidermis, while melanophores, xanthophores, and iridophores are found within the dermal layer. The skin also exhibits well-developed peripheral nerves, blood vessels, and subcutaneous muscles. Immunofluorescence staining further elucidates the distribution and localization of various skin cells. E-cadherin and CK14 are strongly expressed in the epidermal layers, excluding the corneous material. E-cadherin surrounds keratinocyte cells in the epidermis, facilitating cell-cell adhesion, while CK14 is present inside the keratinocyte cells, contributing to their internal structural integrity. Sox10 and CD117 identify the four chromatophore types, with Melan-A specifically detecting only melanocytes and melanophores and not labeling xanthophores and iridophores. Tom20 is used to detect mitochondrial distribution and intensity in the skin, revealing a high density of mitochondria in all epidermal layers, especially in melanocytes and melanophores, compared to xanthophores and iridophores. Numerous telocytes, spindle-shaped with extensions called telopods, are detected in the dermis using CD34, PDGFRα, and vimentin. The skin of the red-eared slider also shows abundant myofibroblasts and well-developed vascularization, with numerous blood vessels detected using α-SMA. This novel study offers an in-depth examination of the limb skin of the red-eared slider through the use of 10 distinct antibodies, uncovering the intricate interactions among its cellular components and providing valuable insights into its anatomical structure and physiological adaptations. Our findings contribute to a better understanding of the turtle's skin, which may aid in its conservation and management.