Stage V of tail regeneration. Eublepharis macularius. (A,B) Gross morphology of the regenerating tail in caudal (A) and dorsal view (B). The regenerating tail is an elevated dome with a length: diameter between 0.5 and 1.0. Serial sections (dorsal towards the top) stained with hematoxylin and eosin (C), Masson's trichrome (D,G,F), Alcian blue (E,H) or immunostained with Sox9 (I). (C-F) Early stage V. (C) Sagittal section of tail with the developing blastema (right side of image) shaped like an elevated dome. (D) Closer view of the region identified in panel (C) taken from a different section. Note the wound epithelium and underlying blastema. (E) Closer view of the region identified in panel (C) taken from a different section. In this image the precartilaginous mesenchymal condensation is visualized by weakly positive staining for Alcian blue. (F) Transverse section through the regenerate tail depicting early muscle formation (stained red) and precartilaginous mesenchymal condensation surrounding the ependymal tube. (G-I) Late stage V. (G) Closer view of epidermal ingrowths, the first evidence of scalation. (H) Parasagittal section through developing cartilaginous cone visualized by strong, positive staining for Alcian blue. (I) Closer view of cartilage cone immunostained for Sox9 (brown), to identity differentiating chondrocytes, and counterstained with hematoxylin (blue). bl, blastema; bv, blood vessel; cc, cartilage cone; co, mesenchymal condensation; em, epaxial muscle; et, ependymal tube; hm, hypaxial muscle; no, notochord; rm, regenerated muscle; sc, spinal cord; we, wound epithelium. Scale bars: c = 20 μm; d = 500 μm; e-g = 100 μm.