Fig. 3. Location of various transporters on the gills of tilapia (A, left) coho salmon (A, right) and rainbow trout (B). CFTR, cystic fibrosis transmembrane regulator-like anion channel; NKA, Na⁺/K⁺ ATPase; AE, anion exchanger; V-ATPase, a proton pump: NHE, a Na⁺/H⁺-like exchange carrier; NKCC, an Na⁺/K⁺/2Cl^– cotransporter; PVC, pavement cell; fwCC, freshwater chloride cell; CC, chloride cell; MR cell, mitochondria-rich cell; AC, accessory cell. (Modified from Wilson and Laurent, 2002.)