Figure 1

Localization and embryonic development of caudal primary scales and oral teeth in the dogfish. A: ventro-lateral view (anterior is to the left) of a 6 cm long embryo stained with alcian blue (cartilage) and alizarin red (prismatic calcified cartilage and dentine); insets: left panel is a ventral view (anterior is to the top) of the lower jaw showing the first mineralized tooth (white arrowhead), right panel is a close-up lateral view (anterior is to the left) of the very tip of the tail showing the bilateral dorsal and ventral rows of caudal primary scales. B-D: caudal primary scale organisation, anterior is to the left and dorsal to the top in all pictures. B: left lateral view of the tail of a 3 cm long embryo after alizarin red staining showing seven buds in the dorsal row and six on the ventral one. Rostral buds are less developed than caudal ones; only the caudal-most buds show alizarin red staining (close up in C, arrowhead). D: left lateral view of the tail of a 7 cm long embryo showing alizarin red stained caudal primary scales. All primary scales are fully developed. Primary scales of the right side are out of focus. E-F: dorsal views of lower jaws after alizarin red staining, anterior is to the top; E: 7 cm long embryo, the four first teeth of the first row are stained (arrowheads) and the following are beginning to mineralize (arrow); F: 7.5 cm long, teeth of the second row (arrows) intercalate between teeth of the first row. Scale bars: A: 0.4 cm; insets 400 μm; B: 200 μm; C: 100 μm; D-F: 400 μm; dcs: dorsal caudal scale, vcs: ventral caudal scales, s: symphysis.