The mechanoreceptors in hatchling and adult Elasmobranch skin.

The skin is the most extensive organ in vertebrates, composed of two layers: the epidermis and the dermis. Sensory axons originating from the dorsal root ganglia innervate the skin mechanoreceptors in the dermis. Elasmobranchs, which appeared 380 million years ago, are characterized by rough skin composed of dermal denticles. While we know about the epidermis and dermis of elasmobranchs, we do not know much about the presence or abundance of mechanoreceptors in their skin. Using the classic histological hematoxylin and eosin method, we examined the skins of hatchling embryos and adults Batoidea (skates and rays) and Selachimorpha (modern sharks). Our histology findings provide substantial evidence to identify structures with similar morphology to traditional mammalian and reptilian mechanoreceptors like Pacinian and Meissner corpuscles. An interesting observation was the presence of Pacinian in the skin of Batoidea but not in the skin of a Selachimorpha Squalus shark.