Fig. 3. Staining for bone in vivo with calcein is more sensitive than traditional Alizarin Red histology. Note how the frontal bones (arrows), left parietal bone (p), dorsal fin rays (df), and much of the axial skeleton stain clearly with calcein, but remain unstained by traditional Alizarin Red. (A) Bone (Alizarin Red) and cartilage (Alcian Blue); (B) fluorescent calcein stain for bone. Both larvae are late pre-metamorphic (14 d.p.f.). Bars, 0.5 mm.