Organization of the regenerating RNC during the late regenerate phase (21+ days after injury). (A, B) Regenerating radial organ complex as viewed form the coelomic side of the body wall on day 28 and day 42 post-injury. Arrowheads indicate the regenerated radial organ complex bridging the wound gap. The shape of the regenerated structure in (A) suggests that the growing regenerates were not aligned along the same axis, but, nevertheless, were able to meet and fuse. (C – H) Longitudinal sections through the regenerated RNC. (C) General morphology of the regenerated radial organs on day 21 post-injury; hematoxylin and eosin staining. (D) Double immunolabeling of the RNC on day 21 post-injury with the ERG1 (magenta) and anti-RS AFRU (green) antibodies. Note that the radial glial cells of the newly regenerated segment of the RNC fully restored their palisade-like morphology and fully resumed their ability to produce and secrete the RS-like material. (E – F’) Double labeling with the glial marker ERG1 (magenta) and the neuronal marker anti-GFSKLYFamide antiserum (green) of the newly regenerated segment of the RNC (E, E’) and the region not affected by the injury (F, F’) on day 21 post-injury. (E’) and (F’) show the labeling with the anti-GFSKLYFamide antiserum in a separate channel. Note that the neuropil on day 21 has not yet completely restored its normal organization (compare with Figure 7). (G, H) Double labeling of the newly regenerated segment of the RNC with the glial marker ERG1 (magenta) and the anti-GABA (G) or the anti-Nurr1 antisera (H) (green) on day 21 post injury. bw, body wall connective tissue; c, coelom; ce, coelomic epithelium; ec, epineural canal; en, ectoneural neuroepithelium; hc, hyponeural canal; hn, hyponeural neuroepithelium; re, roof epithelium; roc, radial organ complex; wvc, water-vascular canal.