Meeting Abstract

P1.77  Jan. 4  Salinity-stimulated induction of carbonic anhydrase in the gills of the green crab, Carcinus maenas CAMMACK, L*; JILLETTE, N; HENRY, RP; Auburn University; Mount Desert Island Biological Laboratory; Auburn University

The enzyme carbonic anhydrase (CA) is an important molecular component of low salinity adaptation in the gills of C. maenas. CA activity is induced 10 fold during transfer from 32 to 10 ppt salinity. Most studies of transport enzyme induction involve salinity transfers over large ranges across which the animal goes from being an osmoconformer (the ion transport processes are turned “off”) to an osmoregulator (transport processes are “on” and presumably operating at their maximum). This study examines CA induction for salinity transfers of 32 to 25 ppt (“off” to “on”) and 25 to 15 ppt, in order to determine if there are differences in the pattern of CA induction if the mechanism has already been turned on. Crabs were transferred to the test salinity for 1 wk, hemolymph was sampled, and gills (G4 and G8) were dissected for analysis of CA activity. For both transfers, hemolymph osmolalilty stabilized to new, acclimated values by 24 hr post-transfer. Initial induction of CA activity in G8 took place at 3-4 days after transfer from 32 to 25 ppt, and activity doubled by 7 days post-transfer. There was a similar time course of CA induction in crabs transferred from 25 to 15 ppt, with the initial increase in activity occurring at 3-4 days post-transfer. The absolute value of the induction was higher for transfer to the lower salinity. There were no changes in CA activity in G3 for either transfer. It appears that pre-activation of the CA induction mechanism does not alter the time course for subsequent salinity-stimulated induction. Changes in CA mRNA are currently under analysis. Supported by NSF 02-3005 to RPH.