Morphological, histological and gene expression changes associated with X. laevis intestinal remodeling during natural metamorphosis. Representative metamorphic stages and the corresponding intestine evaluated with H&E (arrowheads indicate the islets of proliferating cells), TUNEL assay (arrows indicate the apoptotic cells), and BrdU immunohistochemistry (arrows indicate proliferating cells). Scale bar = 100 μm. AE:adult epithelial; Ct: connective tissue; Ep: epithelium; m: muscle; Ty: typhlosole. The schematic representation at the bottom summarizes the major changes associated with the stage-dependent transition.