Fig. 2. SEM showing the surface of gill filaments of tilapia adapted to 35–55 g l^–1 salinity for 14 days. (A) Middle of gill filament from 35 g l^–1-exposed fish; the rectangle marks the area examined on the trailing edge. L, secondary lamellae; LE, leading edge; TE, trailing edge. (B) Filamental epithelial surface from 35 g l^–1-exposed fish; arrows indicate the chloride cell apical pits. MC, mucus cells; PC, pavement cell. (C) Filamental epithelial surface in 45 g l^–1-exposed fish. (D) Filamental epithelial surface in 55 g l^–1-exposed fish. Scale bars: 100 µm (A), 10 µm (B–D).