Figure 3

Cell proliferation in regenerating polyps. (A-D; I-L) Nuclei of proliferating cells (green) labeled with the thymidine analog EdU (Molecular Probes, Eugene, OR, USA), and all nuclei counterstained with Hoechst (blue). (E-H; M-P) Nuclei of proliferating cells labeled with EdU (green). (A, E) Cut site on the aboral fragment of bisected polyp, 1 hpa. Low numbers of proliferating cells are observed. (B, F) Cut site 18 hpa, with low numbers of proliferating cells. (C, G) 24 hpa, high numbers of proliferating cells are detectable close to the site of amputation. (D, H) 36 hpa, high numbers of proliferating cells are detectable in the region of the cut site, including in the emerging tentacle buds. (I, M) 48 hpa, high numbers of proliferating cells are detectable in the regenerating oral structures, including the tentacle buds and pharynx. (J, N) 72 hours after amputation. (K, O) 96 hpa. (L, P) 120 hpa, fewer proliferating cells are detected. (Q) Chart of levels of cell proliferation in the ectoderm during regeneration. (R) Chart of levels of cell proliferation in the endoderm during regeneration. Values are the mean of measurements for at least 4 polyps at each time point. Error bars: standard error. Scale bars = 50 μm.