In the Meckel’s cartilage (MC) element, immobilisation had the most pronounced effects on rudiment depth.

(A) Brightfield ventral view of a 7 dpf zebrafish head expressing Tg(Col2a1aBAC:mCherry) cartilage marker showing the location of the jaw joint (yellow box). (B) 3D views of the jaw in the ventral and lateral planes illustrating the anterior Meckel’s cartilage (MC) element. (C) Shape outlines of average MC shape at 4, 4.5 and 5 dpf for free-to-move (a, b) and immobilised (c, d) larvae. (D–F) MC length (D), depth (E) and width (F) measurements taken on individual larvae from the free-to-move (n = 4 per group) and immobilised larvae (n = 3 per group) at 4, 4.5 and 5 dpf. Bars indicate significant differences (p<0.05) between the free-to-move and immobilised groups at 5dpf; no statistically significant differences were found between the ages with each group, or between free-to-move and immobilised groups at 4 or 4.5 dpf. An: Anterior, CH: Ceratohyal, Dr: Dorsal, L: Lateral, M: Medial, MC: Meckel’s cartilage, P: Posterior, PQ: Palatoquadrate, V: Ventral.