C. sap&, acclimating to dilute media. However, because hemolymph osmotic pressure rapidly decreased and then came to a new steady state only 12-48 h after transfer to 50% SW in the present study, it is clear that rapid in viva modulation of ion transport by existing
enzyme in gills also occurs. It may be that these short-term changes occur, as in cultured mammalian cells, by stimulation of Na, K-ATPase activity by changes in intracellular Na+ concentration (23) and/or by addition of K+ “leak” channels in the basolateral cell membranes (29). Robinson (26) has recently demonstrated modulation of unidirectional **Na fluxes across the gills of C. sapidus subjected to rapid changes in external salinity.