Ultrastructure of Intestinal Epithelium in Cartilaginous Fish

Resumo

By means of electronic microscopy, the structural distinctions of epithelial cells are revealed in three species of cartilaginous fish differing in their foraging: spiny dogfish Squalus acanthias (a typical fish predator), common stingray Dasyatis pastinaca, and thornback ray Raja clavata (benthos eaters-facultative fish predators). In the spiny dogfish, the length of microvillu in the brush border of enterocytes in the medial region of the spiral intestine is smaller than in Dasyatis pastinaca and Raja clavata (0.66 ± 0.05 vs. 1.16 ± 0.07 and 1.04 ± 0.10 μm) and their diameter, on the contrary, is greater (0.10 vs. 0.08 and 0.07 μm). In Dasyatis pastinaca, there is a well-developed glycocalix and the distal decrease of microvilli length. The role of the brush border enetocytes in the increase of digestive and transport surface of the intestine, as well as the role of particular organelles in digestions and transport of nutrients in the investigated fish, is discussed.