Transepithelial potential differences and Na+ fluxin isolated perfused gills of the crabChasmagnathus granulatus (Grapsidae) acclimatedto hyper- and hypo-salinityC. M. Luquet1,*, U. Postel2, J. Halperin1,3, M. R. Urcola1, R. Marques4 andD. Siebers21 Department of Biological Sciences, FCEN University of Buenos Aires, Building II, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina,2 Alfred Wegener Institute for Polar and Marine Research, Columbusstrasse, D-27568 Bremerhaven, Germany,3 CONICET-Argentina and4 Department of Inorganic Chemistry, FCEN University of Buenos Aires, Argentina*e-mail: luquet@bg.fcen.uba.arAccepted 1 October 2001We studied the transepithelial potential difference (TEPD) and 22Na flux across isolated perfused gills (anteriorpair 5 and posterior pairs 68) of the crab Chasmagnathus granulatus acclimated to either hypo- or hyper-osmoticconditions.The gills of crabs acclimated to low salinity, perfused and bathed with 10 saline solutions, produced the followingTEPDs (hemolymph side with respect to bath side): 0.4±0.7, 10.2±1.6, 10.8±1.3 and 6.7±1.3 mV for gills 5, 6, 7and 8, respectively. Gills 6, 7 and 8 did not differ significantly. Reducing the saline concentration of bath andperfusate from 30 to 20 or 10 increased significantly the TEPDs of these gills. TEPDs of gill 6(representative of posterior gills) were reduced by 69±5 % and 60±5 % after perfusion with ouabain or BaCl2(5 mmol l1 each), respectively. The same gill showed a net ouabain-sensitive Na+ influx of1150±290 µequiv g1 h1.Gill 6 of crabs acclimated to high salinity produced TEPDs of 1.5±0.1 and 1.3±0.09 mV after perfusion with 30or 40 salines, respectively. Perfusion with ouabain or BaCl2 reduced TEPDs by 76±7 % and 86±4 %,respectively. A net ouabain-sensitive Na+ efflux of 2282±337 µequiv g1 h1 was recorded in gill 6 perfused with 38saline.Key words: isolated perfused gill, transepithelial potential difference, Na+K+-ATPase, ion flux, hypo-regulation,hyper-regulation, ouabain, crab, Chasmagnathus granulatus.© The Company of Biologists Ltd 2002