Fig. 2

Histology and gene expression in the developing odontodes of Scyliorhinus canicula and Raja clavata. Lower jaw longitudinal sections (anterior, left; dorsal, up) of a 20 cm long S.c. juvenile (a), a 9 cm long S.c. embryo (b-f), and a 9 cm long R.c embryos (m-r), revealing the presence of tooth series at the maturation stage as well as less developed secretory stage tooth bud harboring columnar ameloblasts (black arrowhead). Thoracic transverse sections are shown for of 6 cm (g-l) and 7 cm (g’-l’) long S.c. embryos, focusing on developing primary dorsal dermal denticles at late morphogenesis and late maturation stage, respectively (dorsal to the top). Sections were stained with HES (a, g, g’, m) or in situ hybridized against SPARC (b, h, h’, n), SPARC-L (c, i, i’, o), Col1a1 (d, j, j’, p), Col1a2 (e, k, k’, q) and Col2a1-L (f, l, l’, r). The asterisks locate the mineralized matrix in teeth and denticles at the late mineralization stage, separating the ameloblasts (Am, located by the dashed lines) from the odontoblasts (Od, delineated by the orange line). MC: Meckel. The scale bar in (a) represents 100 μm in (a-f, m-r), and the scale bar in (g) represents 50 μm in (g-l’)