Differential induction of branchial carbonic anhydrase and NA(+)/K(+) ATPase activity in the euryhaline crab, Carcinus maenas, in response to low salinity exposure.

The time course of induction of activity of carbonic anhydrase (CA) and Na/K ATPase, two enzymes that are central to osmotic and ionic regulation in the eyryhaline green crab, Carcinus maenas, was measured in response to a transfer from 32 to 10 ppt salinity. CA activity was low in all gills in crabs acclimated to high salinity. Activity was induced in the posterior three gills (G6-G9) starting at 96 hr following transfer to low salinity, with activity peaking at seven post-transfer.