May modulate the activity of a sodium/potassium-transporting ATPase. Detected in adult gill and in larval skin at 2 days post-fertilization (at protein level). In adult gill, strong expression is found in the basal regions of the secondary lamellae. Expressed from 1 day post-fertilization. Induced in larvae and adult gills by low salinity and repressed by high salinity. Morpholino knockdown of the protein results in an increased number of sodium/potassium-transporting ATPase-expressing cells in larval skin. Belongs to the FXYD family.