Stage II of tail regeneration. Stage II of tail regeneration. Eublepharis macularius. (A,B) Gross morphology of autotomy surface in caudal (A) and dorsal view (B). Non-skeletal tissue has retracted from the autotomy surface further exposing the fractured vertebra. Serial sections stained with Masson's trichrome (C,D,F) or immunostained with PCNA (E,G) (dorsal towards top of page, autotomy surface to right). (C) Sagittal section of tail. The spinal cord (stained pink) is centrally positioned. Ventral and parallel to the spinal cord is the notochord (in this view stained red with green mottles). The centrally positioned skeleton is surrounded by bands of adipose tissue (unstained) and skeletal muscle (stained red). Note the recesses for projecting muscle processes from the autotomized tail (black asterisks). (D,E) Closer views of the region identified in panel (C) taken from different sections. Note the wound epithelium developing deep to the clot. Most of wound epithelium cells are positive for PCNA (immunostained brown) indicating they are proliferating (E). (F) Closer view of a multinucleated chondroclast and associated Howship's lacuna carved into cartilage (stained green). (G) Longitudinal sections immunostained for PCNA (brown) and counterstained with hematoxylin (blue) identifies proliferating cells in the early blastema and some of the surrounding tissues (G). at, adipose tissue; bl, blastema; cl, clot; cv, caudal vein; de, dermis; nc, notochordal cartilage; no, notochord; ns, neural spine; sc, spinal cord; sp, arterial sphincter; we, wound epithelium. Scale bars: c = 500 μm; d-f = 20 μm; g = 50 μm.