Fig. 2. Intracellular P_O2 (kPa) in slow pectoral muscle fibres of notothenioids from the sub-Antarctic region. The integrated response of differences in fibre radius and intracellular compartments is predicted to maintain a similar level of tissue oxygenation at cell temperatures experienced during winter (A–D) and summer (E–H) (4 and 10°C, respectively). The icefish Champsocephalus esox shows a potential hypoxaemia that is particularly evident at the higher temperature (H).