Histological Studies on the Skin of a Freshwater Goby Rhinogobius brunneus (Gobiidae) Related to Cutaneous Respiration

Abstract: The Korean freshwater goby, Rhinogobius brunneus, prefers shallow water bodies with pebble bottoms, which are easily exposed to air due to the lack of water in droughts or the decline of water level after rainfall. Histological studies using microscopic researches revealed its skin consisting of two large parts, the epidermis and dermis with modified vascularization and intraepithelial blood capillaries, considering such environmental habitat conditions. The epidermis (38.4–156.8 µm in thickness) is classified into three parts; the outermost surface layer contained: stratified squamous and polygonal cells, mucous cells, and taste buds. The middle layer includes stratified polygonal cells and finally, the stratum germinativum consisting of a single layer of stratified polygonal cells and intraepithelial blood capillaries. In particular, there are very interesting findings that a small number of blood capillaries are situated at the stratum germinativum of the epidermis and dermal vascularization develops at the stratum laxum of the dermis. Consequently, the presence of the intraepithelial and intradermal blood capillaries, abundant mucous cells, well-developed dermal vascularization, a thick epidermis, as well as the reduced diffusion distance in some skin regions may be considered useful histological evidence to support cutaneous respiration during hypoxic conditions in stagnant water or during the periodic dry season.