Fig. 4. CA activity (µmol CO₂ mg protein^-1 min^-1) in anterior (G3, white bars) and posterior (G7, dark bars) gills of Callinectes sapidus acclimated to 35 p.p.t. (t=0) and at various times after being transferred to 15 p.p.t. Values are means ± s.e.m., N=6–18. Letters above bars indicate statistical comparisons within G7 across the time course: two columns not sharing at least one same letter are statistically different (P<0.05, two-way ANOVA, Tukey's post-hoc test). There were no significant differences among G3.