Active NaCl absorption across split lamellae of posterior gills of Chinese crabs (Eriocheir sinensis) adapted to different salinities

Abstract Split lamellae of posterior gills of Eriocheir sinensis adapted to fresh water, brackish waters (9 or 18‰) or seawater (36‰) were mounted in Ussing chambers, and transepithelial short-circuit currents and conductances were measured with salines, containing approximately in vivo-like NaCl concentrations. Active sodium and chloride absorption ( I Na and I Cl ), the transcellular conductances and the leak conductance were identified with external amiloride and/or DIDS. Split gill lamellae of crabs adapted to fresh water displayed similar magnitudes of I Na and I Cl with 10 mmol l −1 NaCl in the external medium (internally haemolymph-like NaCl saline). Augmenting external NaCl (50 mmol l −1 ) resulted in an increase of I Cl , whereas I Na decreased. Split gill lamellae of crabs adapted to brackish waters (external NaCl of 125 and 225 mmol l −1 , respectively) showed lower currents than preparations of freshwater crabs (50 mmol l −1 external NaCl). With split gill lamellae of seawater crabs no currents were detected (450 mmol l −1 NaCl on both sides). The transcellular conductances showed similar changes as the currents. The leak conductance of split gill lamellae of crabs adapted to fresh or brackish waters was low (0.3–0.8 mS cm −2 ), whereas it was much higher (7 mS cm −2 ) with preparations of seawater crabs.