Fig. 8

Epithelial apoptosis takes place prior to the appearance of clusters (islets) of proliferating adult intestinal stem cells during natural metamorphosis. Tadpoles at premetamorphic stage 54 (A), climax (B stage 60, C stage 62), and end of metamorphosis (D stage 66) were injected with EdU 1 h before being sacrificed. Cross-sections of the intestine from the resulting tadpoles were double-stained for apoptosis by TUNEL and for EdU. Higher magnifications of boxed areas in (A–D) are shown in (a′–d′). The dotted lines depict the epithelium-mesenchyme boundary (see Fig. 1)