[Remodeling of small intestine with metamorphosis in tadpoles (Rhacophorus owstoni)].

The alimentary canal of typical anurans is remodeled during metamorphosis. We examined the tissue structure of small intestine in tadpoles of the treefrog, Rhacophorus owstoni. The cytoskeletal components of the smooth muscle cells were identified by immunohistochemically with alpha-smooth muscle actin antibody. Before metamorphosis, the smooth muscle fibers are arranged in two layers that are circular and longitudinal in orientation, and are stained markedly brown. During metamorphosis, there was concomitant increase in the number of muscle fibers per unit length of tract in both layers. By the end of the metamorphosis, the alimentary tract are transformed morphologically from the larval to adult form, and the smooth muscle cells are rapidly increasing in number. This study suggests that the structural change of musculature are formed in rearrangements of smooth muscle cells, but no proliferation of these cells with the metamorphosis.