Anuran‐like Aquaporins in the Skin and Urinary Bladder of a Urodele, Evidence for Early Gene Duplication in the Lissamphibia

Abstract

Amphibians are unique among vertebrates in that they obtain water primarily by absorption across their skin. In anurans this is mediated by specific aquaporins (AQPa2 homologs) that become inserted into the apical membrane of the outer most living cell layer in response to dehydration or treatment with arginine vasotocin (AVT). The urinary bladder epithelium also expresses an AQPa2 homolog to regulate the reabsorption of dilute urine when the animals are away from water. Recently, an ortholog of human AQP5 (AQP5a) has been identified in the bladder of the aquatic anurans Xenopus laevis and X. tropicalis that were exposed to dehydration. Here we report the identification of an AQP-a2-like aquaporin (AQP-nv3) in the skin and an AQP5a-like aquaporin in the urinary bladder of the urodele, Notopthalmus viridescens. These results suggest the gene duplication and co-optation of aquaporins to the skin and urinary bladder occurred early in the phylogeny of the lissamphia, prior to the breakup of the Pangea supercontinent. Supported by Grants-in Aid for Scientific Research (26440165) from the Ministry of Education, Culture, Sports, Science and Technology of Japan