Although there have been a few studies investigating the location of teleost fish aquaporins. To date little is still known concerning this topic. In the eel, eleven aquaporin genes have been cloned and sequenced from osmoregulatory tissues such as gill, gut and kidney and custom antibodies raised against specific aquaporin peptide antigens. Results show that eel aquaporin 1 (aquaporin 1) is expressed in the apical membranes of a subset of renal tubules and in endothelial cells lining blood vessels as shown previously. A duplicate copy of aquaporin1, AQP1dup (AQP1b using zebrafish nomenclature) was also expressed in a subset of renal tubules but was located in vesicles in the apical pole of the tubule cells rather than in the apical membrane. Aquaporin 8 (AQP8ab in zebrafish) was also expressed in a subset of renal tubules but was located in the basal pole of cells and also stained red blood cells, whereas AQP8b (AQP8aa in zebrafish) expression was located in and adjacent to, cells expressing chromogenic pigment granules. Aquaporin 4b, a novel eel aquaporin was expressed in lines or rings of cells, in unknown structures not associated with either renal tubules or blood vessels. For aquaglyceroporins, AQP3 stained only red blood cells whereas AQPe (AQP10b in zebrafish), stained connective tissue with weak staining in the basal pole of some renal tubules.C.P. Cutler is funded by the National Science Foundation NSF IOS 0844818.