Fig. 1.

Schematic illustrations of the layers within the vertebral body of the Atlantic salmon. The layers are displayed both in medial section and within the whole vertebra. The main direction of the collagen fibres within the matrix of each layer is indicated by lines. (A) Layer 1 (chordacentrum), which forms through mineralization of the notochordal sheath, is shown in red. (B) Layer 2 is a continuous, thin layer that encases the entire notochord. The vertebral part of the layer is shown in green, and the part that participates in forming the intervertebral ligament is in light green. (C) Layer 3 is shown in blue, and makes up the bulk of the laminar bone within the amphicoel. (D) Layer 4 is shown in yellow, and consists of cancellous bone, mainly with an interconnected mesh of longitudinal and transverse trabeculae.