Fig. 1From: Skeletal regeneration in the brittle star Amphiura filiformis Early stages of arm regeneration in the brittle star Amphiura filiformis. A) Schematic diagram of early arm regeneration stages and average timing to those stages, based on morphological landmarks. Stage 1-wound healing and re-epithelialization. Stage 2-regenerative bud formation. Stage 3-appearance of the radial water canal, coelomic cavities (aboral coelomic canal, ectoneural and hyponeural sinuses) and radial nerve in the regenerative bud. Stage 4-appearance of first metameric units (arm segments). Stage 5-advanced extension of arm, formation of several metameric units at proximal end. B–E) Oral view of fixed arms at stages 2 (B), 3 (C), 4 (D) and 5 (E) shown using differential interference contrast (DIC) microscopy. C’) Detail of C focusing on dermal layer. D’) Detail of D. E’) Detail of E. Arrows - the dermal layer, asterisk - cuticle, D - distal, L - left, OV - oral view, P - proximal, R - right, RWC - radial water canal, S - spiculeBack to article page