Fig. 1. Temperature dependence of the respiration rates in (A) North Sea and (B) White Sea Littorina saxatilis acclimated to 13°C and 4°C. High critical temperatures (T_c II^c and T_c II^w in cold- and warm-acclimated animals, respectively) are indicated by arrows. These are the temperatures where an onset of anaerobiosis occurred as determined by significant succinate accumulation compared with the respective control level (see Fig. 3). N=6-16 for each data point.