Two types of AQP5 genes (aqp-xt5a and aqp-xt5b) were identified in the genome of Xenopus tropicalis by synteny comparison and molecular phylogenetic analysis. When the frogs were in water, AQP-xt5a mRNA was expressed in the skin and urinary bladder. The expression of AQP-xt5a mRNA was significantly increased in dehydrated frogs. AQP-xt5b mRNA was also detected in the skin and showed an increase in its expression in response to dehydration. Additionally, AQP-xt5b mRNA began to be slightly expressed in the lung and stomach under dehydration. For the pelvic skin, immunofluorescence staining localized AQP-xt5a and AQP-xt5b to the cytoplasm of secretory cells of the granular glands and the apical plasma membrane of secretory cells of the small granular glands, respectively, in normally hydrated frogs. Under dehydration, the locations of both AQPs in their respective glands did not change, but AQP-xt5a appeared in the cytoplasm of secretory cells of the small granular glands. For the urinary bladder, AQP-xt5a was observed in the apical plasma membrane and cytoplasm of a number of granular cells under normal hydration. In contrast, AQP-xt5a was found in the apical membrane and cytoplasm of most granular cells after dehydration. Injection of vasotocin into hydrated frogs did not induce these changes in the localization of AQP-xt5a in the small granular glands and urinary bladder, however. The results suggest that AQP-xt5a might be involved in water reabsorption from the urinary bladder under dehydration, whereas AQP-xt5b might play a role in water secretion from the small granular gland.