title: Metamorphic changes in the stomach of the frog Rana temporaria tadpoles.
abstract: The histological transformation of amphibian stomach during metamorphosis was studied in the frog Rana temporaria. The earliest metamorphic changes occur shortly before regression of the cloacal piece of tail and appearance of forelegs. Autolysis of primary, larval epithelial cells and activity of phagocytes lead to regression of the apical mucosa, which is shed into the gastric lumen. Histogenesis takes place from the very beginning of metamorphosis in the basal region of the mucosa; undifferentiated, regenerative cells, arranged in small compact cords and surrounded by a thick basement membrane, give rise to secondary lining epithelium and glands. Lining epithelial cells differentiate into a typical mucosecretory epithelium. Oxyntic cells present in larval glands are substituted by both ion- and protein-secreting oxyntic-peptic cells. During metamorphosis, connective and muscular tissues markedly increase, a submucosa, not present in larval tadpoles, gradually develops. A muscularis mucosae is also formed and the muscular propria becomes thicker. At late metamorphosis, folded structures involving both mucosa and submucosa develop, increasing the luminal surface as in adults. Removal of the larval gastric mucosa and its replacement by a new, adult-type definitive one, together with development of peripheral connective and muscular tissues, account for metamorphosis of tadpole stomach.
authors.affiliation: Department of Histology and Pathology, University of Navarra, Pamplona, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Rovira
authors.forename: A C
authors.initials: AC
authors.lastname: Villaro
authors.forename: M E
authors.initials: ME
authors.lastname: Bodegas
authors.forename: E
authors.initials: E
authors.lastname: Valverde
authors.forename: P
authors.initials: P
authors.lastname: Sesma
mesh_terms: D000818:Animals; D005753:Gastric Mucosa / Q000254:growth & development; D007814:Larva / Q000254:growth & development; D008675:Metamorphosis, Biological; D008854:Microscopy, Electron; D016613:Plastic Embedding; D011896:Rana temporaria / Q000254:growth & development*; D013270:Stomach / Q000254:growth & development*