F-actin musculature (green, first and third column) and serotonergic nervous system (red, second and fourth column) in posterior regenerates; anterior is up. (A, B) 1 hour post-amputation: constricted ring musculature, wound not yet closed. A few autofluorescent gland cells are marked with white asterisks. (C, D) 6 hours: fine network of muscle fibres covers wound (white arrowhead); main nerve cords start reorganizing (hollow arrowheads). (E, F) 12 hours; advanced wound closure (white arrowhead), serotonergic fibres are comparable to 6-hour-old regenerates. (G, H) 24 hours: wound closure by muscle fibres is complete (inset in G), former wound is still visible as small serotonergic ring (arrowheads in (H) and inset). (I, J) 36 hours: first pharyngeal actin filaments (note fine muscle fibres beneath two white arrowheads); blastema area can be estimated by weaker staining of fine muscle network at posterior site (dashed line); new nerve cell bodies (hollow arrowheads) appear in blastema, and nerve cords are connected (white arrowhead in J). (K, L) A spherical immature pharynx connected to the epidermis by strong muscle fibres appears, and lumen forms (white double arrow); blastema increases (dashed line). Fine serotonergic nerve fibres can be spotted in the most posterior part (white arrowhead, inset in L). (M, N) Tail and pharynx formation has significantly advanced in the last 24 hours. (M) White arrowhead indicates fissures of transverse muscles beneath outer pharynx epithelium. (N) Serotonergic staining shows nerve fibres within tail plate (white arrowhead) and of mouth (white arrow, detail in inset). (O, P) Regeneration of pharynx and tail are complete. Adhesive systems cover most of tail (see white arrowheads). Mouth nerve fibres are clearly visible (white arrow). Copulatory structures are still missing. Scale bar in (A-P) 50 μm; scale bar in (A) and (E) insets 50 μm; scale bar in (G), (H), (L) and (N) insets 25 μm.