Cellular diversity in the epidermis of Raja clavata (Chondrichthyes)

Abstract

The epidermal layer of the skin of the cartilaginous ®sh Raja clavata taken from a suitable place on the ventral side of the head was examined by light and electron microscopy. Cells of the basal layer divide and differentiate as epithelial cells of the mid-epidermis, characterized by numerous electron-dense, membranebound vesicles; their content is assumed to be mucus. Cells at the super®cial layer of the epidermis lose these vesicles but have a palisade of mucous vesicles below the apical membrane. A modi®ed glycocalyx coats the outer lea¯et of the apical membrane.In addition to epithelial cells, there are epidermal cells differentiated as two kinds of mucous goblet cells, sacciform cells similar to those found in teleost ®sh epidermis, holocrine cells with some resemblance to the club cells of teleosts but differing in their cytology, and chemosensory cells similar to those found in the oral epithelium of Raja. Merkel cells were not found. Cells that might be interpreted as ionocytes were seen but their nature was not con®rmed. The epidermis is penetrated by numerous nerve ®bres; swellings contain mitochondria and glycogen granules. The nerve ®bres also contain 50±70 nm vesicles with an indistinct core. Cells intrusive to the epidermis include melanocytes, lymphocytes, macrophages, and several types of granular leucocyte. The cytology of the various epidermal elements is generally similar to that known in teleost ®shes.

Histochemistry and functional organization of the dorsal skin of Ancistrus dolichopterus (Siluriformes: Loricariidae)

“…This structural similarity between the denticles and the elasmobranch placoid scales shows that a morphogenetic/histogenetic potential has been present in vertebrate skin even since the early times of Agnathan evolution and that such structures were expressed convergently in various groups during fish evolution. The resemblance of the cell types in the epidermis of elasmobranches as Raja to those known from teleost fishes, also support this idea (Whitear & Moate, 1998).…”

A conserved morphogenetic mechanism for epidermal ensheathment of nociceptive sensory neurites

“…Sensory axon terminals in the epidermis of zebrafish larvae and adults are ensheathed by the apical membranes of epidermal keratinocytes (Figure 2A) (O'Brien et al, 2012), and ensheathment channels have also been seen in adult fish (Whitear and Moate, 1998; Rasmussen et al, 2018). These axonal ensheathment channels are remarkably similar at the ultrastructural level to the sheaths wrapping somatosensory dendrites in Drosophila larvae.…”

“…Drosophila and zebrafish epidermal cells wrap sensory neurites by extending membranes around the entire circumference of the sensory neurite. The wrapping epidermal membranes are tightly apposed to one another and the ensheathed neurites, embedding them inside a mesaxon-like structure (Whitear and Moate, 1998; Han et al, 2012; Kim et al, 2012; O'Brien et al, 2012). A similar structure has been documented for ensheathed somatosensory neurites in Caenorhabditis elegans and humans (Cauna, 1973; Chalfie and Sulston, 1981), suggesting that ensheathment by epidermal cells is a conserved feature of sensory endings.…”

Diversity of Lips and Associated Structures in Fishes by SEM

“…Insofar as these structures appeared as micro-ridges under SEM and microvilli under TEM. The term "microridges" is used in this study following Whitear & Mittal (1986), Whitear (1990), Suzuki (1992) and Whitear & Moate (1998) and seems appropriate.…”