Fig. 6. Representative photomicrographs of double labeling for V-H⁺-ATPase-rich (brown) and Na⁺/K⁺-ATPase-rich (blue) in longitudinal sections of gill filaments from freshwater (A), seawater-acclimated (B), and seawater (C) Atlantic stingrays (x400). Scale bars, 100 µm. Note that regardless of salinity there were separate brown and blue cells, indicating the two transporters occur in distinct cell types.