On the epidermal structure of Boleophthalmus and Scartelaos mudskippers with reference to their adaptation to terrestrial life

The skin structures of 4 species of oxudercine gobies (3 species of Boleoph thalmus and 1 species of Scartelaos) were investigated in relation to the t errestrial exposure of these fishes. These species have similarities in bot h lifestyle and skin structure. The specializations for terrestrial life ma inly include the presence of dermal bulges, a thick middle cell layer, and a vascularized epidermis. Moreover, mucous cells are distributed only on th e epidermis where the capillaries are undeveloped. In all species, the derm al bulges are large on the head and dorsal body, which are most often expos ed to the air, and push up a thin epidermis, forming so-called papillae. Ca pillaries are densely distributed on the apical area of each papilla. In Bo leophthalmus, the middle cell layer is thicker. the bulges are larger and d istributed over a greater part of the body, and the area of the skin surfac e having the papillae is larger than it is in Scartelaos. These differences suggest that the contribution of the skin to respiration is comparatively large in Boleophthalmus species. reflecting their more frequent activities on mudflats relative to the activities of the Scartelaos species, which pre fer to stay in the water. Mucous cells are abundantly distributed on the ep idermis surface between the papillae in all species. The separation of the capillaries and the mucous cells may be due to an impeding of gas exchange by the mucus.