Figure 1: Mechanisms of axial elongation in fishes.

(a) Addition of segments, (b) elongation of segments and (c) expansion of intercalaries in lateral view. (d) Relationship between the neural and haemal arches and the notochord in anterior view. Blue represents the neural and haemal arches, red represents the intercalaries, black lines illustrate the epaxial and hypaxial myosepta. HA, haemal arch; NA, neural arch; and VA, ventral arch.