Multicellular complex of chloride cells in the gills of freshwater teleosts

Morphology of branchial chloride cells in the freshwater teleosts Plecoglossus altivelis, Cyprinus carpio, and Oreochromis mossambicus was studied by light and transmission electron microscopy. The chloride cell has an apical membrane directly in contact with the outer medium. Generally, two or more neighboring chloride cells share an apical pit, forming a multicellular complex. The chloride cells form a multicellular complex in which cells differ in cytoplasmic electron density, development of tubular system, and in cell size. Chloride cells are linked by junctions which are shallower than the tight junctions that occur between neighboring pavement cells or between pavement and chloride cells. Multicellular complexes of chloride cells create additional paracellular pathways marked apically by the shallower junctions. Since junctional structure affects transepithelial permeability, development of multicellular complexes of chloride cells in freshwater fishes may be related to the transport of some substances as in the gills of marine fishes.