Morphology of the Skin Glands of the Crab-eating Frog : Rana cancrivora
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The skin glands of Rana cancrivora, the euryhaline crab-eating frog, were examined using histochemistry and immunohistochemistry. The skin contained three different glands : a mucous gland, a mixed gland and a vacuolated gland. The acinar cells of the mucous gland stained strongly with alcian blue at pH 2.5 (AB) and weakly with periodic acid-Schiff stain (PAS). In the acinus of the mixed glands, several kinds of cells could be identified : (1) cells with abundant cytoplasm which stained with PAS in the transition region between acinus and duct ; (2) cuboidal or squamous cells in the apical portion of the acinus ; (3) cells filled with carminophilic granules ; (4) cells containing many large vacuoles which stained by PAS and AB. In the acinus of the vacuolated glands, the nuclei of the epithelical cells were located peripherally and the large lumen was filled with vacuoles. In all gland types, no specific immunoreactivity was detected by immunohistochemistry for thyrotropin releasing hormone, cholecystokinin 10, neuropeptide Y, neurotensin, somatostatin and 5-hydroxytryptamine. These results indicate that the skin glands of Rana cancrivora have a different structure and properties from those of other amphibians studied so far.