Fig. 5. Confocal laser scanning microscopy: dual immuno-localisation of AQP-3 (false colour: red) and Na⁺, K⁺-ATPase (ß233 subunit) (false colour: green) in thin sections. Gill primary and secondary filaments of 3-week seawater (SW)-acclimated (A,B) and freshwater (FW; C,D) silver eels. Intestinal sections of SW-acclimated (E) and FW (F) silver eels. Rectal epithelium of a SW-acclimated silver eel (G). PF, primary filaments; SL, secondary lamellae; E, gut epithelium; L, gut lumen; CC, chloride cell; GC, goblet cell; M, macrophage-like body; RBC, red blood cell; AP, apical pit. Bars, 50 µm (A,E,F,G); 25 µm (B,C); 10 µm (D).