Fig. 4.

Locations where GFCs are found in Botryllus juveniles. a–f Confocal images of clusters composed of vasa-positive germ cells (red) and tgfβ-f-positive follicle progenitors (green) in Botryllus juveniles. a A cluster of germ cells and follicle progenitors in the primary bud niche (pn) is situated just posterior to a developing secondary bud at stage B2 (arrowhead). b A cluster of germ cells and follicle progenitors near the midline of a primary bud (pb) at stage B2. c A cluster of germ cells and follicle progenitors associated with the secondary bud (sb) at stage C1. d A cluster of germ cells and follicle progenitors in the vasculature (v; outlined by dotted lines) at stage B2. e Two clusters of germ cells and follicle progenitors near the stomach of an adult zooid (z) at stage C1. f A cluster of germ and follicle cells in a nodule embedded in the tunic of a stage A2 colony. Scale bars indicate 50 µm. Nuclei are shown by DAPI staining (blue). a′–f′ Schematic diagrams indicating the general locations of each confocal image in a–f (dashed boxes). The red asterisk in f′ marks the epithelium of the stomach’s posterior where GFCs are sometimes found. mv marginal vessel, a ampullae, s stomach