Fig. 5.

Cell proliferation in intact cydippids. A Schematic of the EdU pulse-chase experiment and PH3 immunostaining in intact cydippids. B–D’ Confocal stack projections of whole intact cydippids oriented in a lateral view. White dotted rectangles in B delimit the tentacle bulb (tb) (C–C”) and apical organ (ao) (D–D”) structures showed in higher magnification at the bottom. Nuclei of S-phase cells are labeled with EdU (magenta), M-phase cells are immunostained with anti-phospho-histone 3 (PH3) (green), and all nuclei are counterstained with DAPI (blue). Note that both markers of cell proliferation (EdU and PH3) show the same pattern of distribution along the cydippid’s body. The inset in C’ shows an aboral view of the tentacle bulb after EdU staining. White asterisks in C’ point to the symmetrical populations of intense cell proliferation referred to as aboral/external cell masses (aec). E–G’ Confocal stack projections of whole intact cydippids oriented in a lateral view. The time of the chase is listed at the top of the columns, and the labeling corresponding to each panel is listed to the left of the rows. Nuclei of S-phase cells are labeled with EdU (magenta) and all nuclei are counterstained with DAPI (blue). Note that EdU+ cells migrate from the tentacle bulb to the most distal end of the tentacle (yellow arrows). See Additional file 2 for further detail of EdU pulse-chase experiment in the tentacle bulb. Scale bars = 100 μm. Abbreviations: ao apical organ, tb tentacle bulb, aec aboral/external cell masses, lr lateral ridge, mr medial ridge, cr comb row