Fig. 1

Developmental stages of zebrafish calvaria.

(A) At 6 mm SL, ossification of the supraoccipital bone becomes visible as indicated by the black arrow; frontal bones are not detected yet. The cartilaginous epiphyseal bar is indicated by red arrow. (B) The frontal bones at 7.5 mm SL are outlined by the black dashed line. The supraoccipital bone is indicated by a black arrow in sections A-D. (C) At 8 mm SL, the frontal bones grow along the epiphyseal bar (red arrow) toward the midline, the parietal bones become visible as small radial patches symmetrically located on both sides of the cranium (outlined by the yellow dashed line). (D) At the 11 mm SL stage, the anterior part of interfrontal suture is developed (green arrow); frontal and parietal bones meet at the lateral side (black arrow head), initiating coronal suture formation, which progresses bilaterally toward the midline (purple arrow). The presumptive lambdoid suture develops between the parietal and supraoccipital bones (green arrowhead). (E) At 13 mm SL, all sutures are formed: the interfrontal (green arrow), coronal (black arrowhead), and sagittal suture (red arrowhead) and lambdoid (green arrowhead); the area specified by the black dotted line exemplify the measured area for morphometric study of the interfrontal suture. (F) Adult zebrafish cranium at age eight months, 26 mm SL. The black and yellow dashed lines indicate frontal and parietal bones respectively; the coronal and sagittal sutures are indicated by black and purple arrowheads respectively. (A, B) lateral view of the head; (C-F) Dorsal view of dissected calvaria stained with Alizarin red and Alcian blue. F–frontal bone, P–parietal bone, SOP–supraoccipital bone.