Fig. 3. Carbonic anhydrase activity (A; µmol CO₂ mg protein^–1 min^–1) and mRNA expression (B; relative amounts) in anterior (G4, black bars) and posterior (G8, gray bars) gills of green crabs acclimated to 32 p.p.t. (32) and transferred to 10 p.p.t. for 7 days (10-7days). Values are means ± s.e.m. (N=6). T=12°C. Asterisks indicate statistical differences in G8 from the 32 p.p.t. controls at P<0.05.