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Table 1 Summary of key gross morphological and histological criteria used to define the stages of tail regeneration in Eublepharis macularius

From: A novel amniote model of epimorphic regeneration: the leopard gecko, Eublepharis macularius

Stage Criteria
  → autotomized vertebra exposed but no adjacent muscle or connective tissue retraction
I → spinal cord retracts within neural canal and is capped distally by a small blood clot
  → integument begins to collapse around the wound site
  → autotomized vertebra exposed and adjacent muscles and connective tissues retracted
  → large clot caps entire wound surface
II → integument collapsed around wound site
  → wound epithelium proliferates and begins to spread across autotomy surface deep to clot
  → blastema appears between retracted spinal cord and overlying clot
  → first appearance of multinucleated osteoclasts and chondroclasts adjacent to autotomized vertebra
  → clot is lost and the complete wound epithelium is exposed
  → wound epithelium continues to proliferate and thicken
III → apical epithelial cap forms
  → blastema spreads beyond neural canal to cap distal end of the tail deep to wound epithelium
  → angiogenesis begins within the blastema
  → ependymal tube and axons from the dorsal root ganglia of the original tail begin to grow into blastema
IV → regenerating tail is dome-shaped and wider than long (length: diameter is less than 0.5)
  → regenerating tail is an elevated dome and wider than long (length: diameter is greater than 0.5 but less than 1.0)
V early → earliest appearance of presumptive cartilaginous skeleton around the ependymal tube
  → muscle tissue begins to differentiate
  → regenerating tail is an elevated dome and wider than long (length: diameter is greater than 0.5 but less than 1.0)
V late → keratinization and the formation of scales begins within the epidemis
  → first expression of Sox9 in cartilage cells of regenerating cartilage cone and original tail cartilage
  → regenerating tail is a tapering cone approaching a length: width of 1.0
VI → first appearance of the differentiated dermis
  → differentiation of cartilage, muscle and adipose tissue nearing completion
  → regenerating tail is a tapering cone longer than wide (length: diameter is greater than 1.0)
VI → proximal portion of the regenerate tail is equal in diameter to the distal portion of original tail
  → pigmentation begins