A review of alligator and snake skin morphology and histotechnical preparations

The anatomy, biochemistry, biomechanics, and evolution of reptile integument have been topics of intense interest in the scientific community for at least two centuries. As such, histological techniques were, and still are, employed to provide a comprehensive understanding of the relationships between tissue structure, function, and the evolution of reptile integument. However, histotechnical preparations of reptile skin present many challenges related to the unique microanatomical configuration of the integument in these animals. Reptilian epidermal scales may be thick and corneous and are often not penetrated well by either processing fluids or embedding media. The reptile dermis is a composite of several different tissue types with a range of biophysical properties creating many problems with tissue processing, sectioning, and staining. Further, lepidosaurs (snakes, lizards, and tuataras) exhibit epidermal modifications associated with the shedding cycle (i.e. ecdysis) that may also create histotechnical artifacts. Here, this study reviews the general skin morphology from crocodilians (alligators, crocodiles, and gharials) and lepidosaurs. Common difficulties encountered while preparing this organ for histological examination are explained and highlighted, and technical solutions and protocols are provided that mitigate these problems.