Fig. 7. Variation in type-II mitochondria-rich cell morphology: (A–G) a cell with a relatively small apical opening in an embryo in freshwater (at 0h of freshwater-to-seawater transfer); (H–N) a remaining cell in an embryo transferred from freshwater to seawater (at 72h of freshwater-to-seawater transfer); (O–U) a newly appearing cell in an embryo transferred from seawater to freshwater (at 24h of seawater-to-freshwater transfer); cells with (V–AB) a deep apical opening and with (AC–AI) a wide apical opening in an embryo transferred from seawater to freshwater (at 72h of seawater-to-freshwater transfer). (A,H,O,V,AC) X–Z optical sections, cut at the lines indicated in X–Y optical sections. (B–D,I–K,P–R,W–Y,AD–AF) X–Y optical sections, cut at three different lines indicated in X–Z optical sections: the focus is placed in the outer surface plane of the yolk-sac membrane (B,I,P,W,AD), in the plane through the center of the NCC immunoreactivity (C,J,Q,X,AE) and in the plane through the center of the nucleus (D,K,R,Y,AF). Channels for Na⁺/K⁺-ATPase (red) and NCC (cyan) are merged in A–D, H–K, O–R, V–Y and AC–AF. The merged X–Y images are further merged with corresponding differential-interference-contrast images (E–G,L–N,S–U,Z–AB,AG–AI). n, nucleus. Scale bar, 10 µm.