Fig. 1. A typical type-I cell in the yolk-sac membrane of a tilapia embryo at 0 h of the freshwater-to-seawater transfer experiment. (A,C,E,G) X-Z optical sections, cut transversely at the horizontal lines indicated in H, I and J. (B,D,F,H,I,J) X-Y optical sections, cut transversely at the line indicated in G. The immunofluorescence for Na⁺/K⁺-ATPase, Na⁺/K⁺/2Cl^- cotransporter (NKCC) and cystic fibrosis transmembrane conductance regulator (CFTR) is shown as separate channels (A-F), and the three channels are merged in G and H. The merged X-Y images are further merged with differential interference contrast images (DIC+flu, I,J). n, nucleus. Scale bar, 10 µm.