Light micrographs of gills of white seabass,L. calcarifer. A. Control group showing gill filament (GF), secondary lamellae (SL), nucleated erythrocyte (Er) within capillary lumen delimited by pillar cells (PC), epithelial cells (EC) cover lamellar and interlamellar regions and chloride cells (CC). B. Scanning electron micrograph showing gill filament (GF), secondary lamellae (SL), epithelial cells with microridge pattern (MIR). C–D.Acute exposure at the first 24 h, C. Gills showed extensive edema of epithelial cells (), and blood congestion (arrows) in many areas of secondary lamellae with breakdown of pillar cell system (arrowheads). D. SEM examination showed swelling of secondary lamellae (arrows).