Carbonic anhydrase activity in the gills ofEtroplus maculatus (Teleostei) as a function of salinity acclimation

1. Carbonic anhydrase in the gills of the freshwater teleost,Etroplus maculatus, was demonstrated to be influenced by transfer of the animal to saline media. 2. Sudden and direct exposure of the fish to saline media resulted in a decrease of the enzyme activity. 3. The enzyme activity was reduced gradually with progressive increase of the salinity after two months acclimation of the fish in the medium. 4. It was concluded that reduced carbonic anhydrase activity of the gill on acclimation to higher salinities, is associated with Cl− uptake but not Cl− excretio