Fig. 4. Na⁺/K⁺-ATPase (green) and cystic fibrosis transmembrane conductance regulator (CFTR; red) immunoreactivity in gills of Hawaiian goby acclimated to freshwater (A–C) and 30 seawater (D–F). Double-staining was performed on the same sections, and the images combined in C and F. Images C and F were overlaid (from A,B and D,E, respectively) to highlight the colocalization of Na⁺/K⁺-ATPase and CFTR. The width of each image is 207 µm.