Virtually every tissue is affected during spontaneous metamorphic remodeling of the duodenum. Cross-sections of the duodenum from A–C) wild-type prometamorphic tadpoles NF57; D–F), metamorphic climax NF61; G–I), and the end of metamorphosis NF66. C,F, and I) Cross-sections of the duodenum from tadpoles transgenic for IFABP-GFP. The GFP antibody reaction is green; smooth muscle actin antibody is red. A,D, and G) hematoxylin and eosin. B,E and H) immunoreactivity against endogenous intestinal fatty acid binding protein (IFABP; blue), muscle-specific smooth muscle actin (red), enteric neuron-specific neural beta-tubulin (green); and a nuclear counter-stain (dapi; white) is shown for half of each section. t=typhlosole, c=circular muscle, l=longitudinal muscle. Scale bar in C denotes 0.2 mm length.