Partial Functional Characterization of an Aquaporin 3 Ortholog From the European Eel, Anguilla anguilla

Maintenance of body fluid composition and osmoregulation are essential for metazoan animals to survive. Aquatic animals face the particular problem of directly interacting with an aqueous environment that differs markedly in osmolality from their internal physiology. Freshwater (FW) fish experience driving forces for osmotic water uptake across the exposed epithelial surfaces of the gill and the gut. They compensate by drinking little and producing large volumes of dilute urine. Conversely, marine fish experience osmotic water loss to the sea and compensate by drinking seawater (SW) and excreting the excess salts ingested via the gills and the kidney. A number of species are euryhaline, exhibiting remarkable physiological adaptation as they move at some stage of their life cycle between FW and SW environments. One such example is the European eel Anguilla anguilla , a euryhaline teleost. In order for species such as the eel to acclimate to environments of different salinity, water and ion transport pathways in epithelia which interface with the environment must be under tight regulation.