Localization of aquaporin 1 and 3 in the gills of the rainbow wrasse Coris julis

Ultrastructural and immunohistochemical studies were conducted on the gill epithelium of the Mediterranean rainbow wrasse (Coris julis). We analysed the immunolocalisation of aquaporin 3 (AQP3) and aquaporin 1 (AQP1) in the gills using confocal microscopy. The ultrastructural features of the gill were investigated using transmission and scanning electron microscopy. The C. julis gill apparatus showed structural characteristics typical for Teleostei. Immunolocalization revealed differential localization of AQP1 and AQP3 in the gill epithelium. Double immunolabelling for Na+/K+ ATPase with AQP1or AQP3 revealed that AQP1 is localised in chloride cells, whereas AQP3 is localized in both the chloride cells and the accessory cells. This result suggests an active role of these cells in water/glycerol transport in saltwater fish.