Fig. 5. Carbonic anhydrase activity (µmol CO₂ mg protein^–1 min^–1) in anterior (G4, black bars) and posterior (G8, gray bars) gills of green crabs acclimated to 32 p.p.t. and transferred to 10 p.p.t. for 7 days. 32, 32 p.p.t. acclimated controls; 10 intact, intact crabs transferred to 10 p.p.t. for 7 days; 10 ESA, eyestalk ablated crabs transferred to 10 p.p.t. and assayed after 7 days; 10 ESAinj, eyestalk ablated crabs transferred to 10 p.p.t. and given daily injections of eyestalk extract taken from `donor' crabs acclimated to 32 p.p.t. Values are means ± s.e.m. (N=6–9). T=12°C. Different letters indicate statistical differences at P<0.05 in G8 across treatments.