Light and electron microscopic studies of the skin of the Palembang puffer,Tetraodon steindachneri (Teleostei,Tetraodontidae)

Summary The skin ofTetraodon steindachneri is morphologically and cytologically adapted to the habits and locomotion of the fish, as well as to its ability to expand its body into a nearly spherical shape. Negative buoyancy, which facilitates precise maneuvers near the bottom, is achieved primarily by a very thick dermis. Various special features of the skin enable it to withstand the mechanical stresses of extreme expansion and deep folding: (1) the absence of a covering such as a cuticle on the outer surface of the epidermis, (2) the lack of scales, (3) the pronounced interdigitation of the epidermal cells, (4) the cytoskeleton of the filament-containing cells, and (5) the stratum compactum of the dermis. The spines, which inT. steindachneri can be extended and retracted, are derived, like the spines of diodontidae, from the scales of other teleosts. Each spine comprises cellular and acellular components, which together produce a complicated bilaterally symmetrical structure. Movement of the spines is mainly a passive mechanical concomitant of distension of the body, though active processes cannot be ruled out. The biological significance of the spine apparatus ofT. steindachneri is discussed.Abbreviations af annular fold - amc apical mucous cell - bv blood vessel - bm basal membrane - cf collagen fibers - cfb collagen fiber band - cv central vacuole - d desmosome - de dermis - ed epidermis - f tonofilaments - fcc filament-containing cell - gc granular cell - id interdigitation - md modified dermis - mr microridges - n nucleus - nf nerve fibers - s spine - sc stratum compactum - sk skeleton of spine - sl stratum laxum - smc sacciform mucous cell - sub subcutis - vc vacuole cell