Fig. 1.

Schematic view of the main structural components of the notochord in the Atlantic salmon. The notochord comprises a core of epitheloid cells that is enclosed by an acellular fibrous sheath, which consists of a thin external elastic membrane (light blue), covering a thicker collagenous layer (blue). The cellular core is composed of an inner tube of chordocytes (light green), each with a large, fluid-filled vacuole. The chordocytes are surrounded by a monolayer of chordoblasts (green). The chordoblasts rest on a basal lamina (grey), are germinal and produce the notochordal sheath. For comparison, the notochord of the zebrafish has a similar general structure, except for the chordoblast layer, which consists of thin squamous cells.