Fig. 4. In situ hybridisation localises sbAQP expression in the kidney, gills and gastrointestinal tract. sbAQP was highly expressed in some of the kidney tubules (A) and (C). In the gill, expression was detected along the length of the lamellae with the most intense signal present in the apical cellular region of lamellae (D,F) where the chloride cells (arrows) were localised (F). An intense expression was found in the hind-gut in cells localised in the lamina propria (G) and in cells (arrows) at the interface between the two muscle layers of the gut (I). No sbAQP expression was observed in the liver (J) or in tubules (arrowheads) in control sections of the kidney (B), gills (E) or gut (H). Scale bars, 1 µm. Asterisks indicate haem deposits in the kidney.