Figure 2

Cell proliferation in intact polyps. (A-C) Nuclei of proliferating cells (green) labeled with the thymidine analog EdU (Molecular Probes, Eugene, OR, USA), and all nuclei counterstained with Hoechst (blue). (D-F) Nuclei of proliferating cells labeled with EdU (green). (A, D) Polyp two days after feeding (2 dpf) with Artemia nauplii. Widespread proliferation is visible throughout the polyp, including in the tentacles and the physa. Proliferating cells are absent only from the distal tips of the tentacles (B, E) One week after the last feeding (1 wpf), proliferating cells are still detected throughout the polyp. The numbers of proliferating cells are particularly high in the pharynx and in the oral disc where tentacle buds are emerging. (C, F) Three weeks after the last feeding (3 wpf). Proliferating cells are detected in the tentacles, but are nearly absent from the remainder of the oral disc, pharynx and body column. Weak signal in the directive mesenteries (arrow) is attributable to autofluorescence, detected due to increased gain used during laser scanning confocal microscopy of the sample. (G) Chart of tissue specific levels of cell proliferation in intact polyps 2 dpf, 1 wpf, and 3 wpf. Values are the mean of measurements for 3 polyps at each time point. Error bars: standard error. One asterisk: p value < 0.05; Student’s t-test for 2 dpf versus 1 wpf. Two asterisks: p value < 0.05; Student’s t-test for 1 wpf versus 3 wpf. Scale bars = 200 μm.