Fig. 7. Tissue pH (pH_i) in muscle tissue of different A. opercularis experimental groups. A0–A4 smaller individuals [open circles, N=8–16, shell height 50.34±4.085 mm (mean ± s.d.)], B0–B4: bigger individuals [filled circles, N=9–18; shell height 68.84±2.91 mm (mean ± s.d.)]. Groups with the same letter (smaller individuals=small letters, bigger individuals=capital letters) are significantly different from each other (P<0.001). When more than two groups have the same letter, the group marked with an asterisk is significantly different from the other two groups.