Myoglobin oxygenation and autoxidation in three reptilian species.

Differences between species in the oxygen (O2) affinity (P50) of myoglobin (Mb) may serve to fine tune O2 supply to cardiac and skeletal muscle in ectotherms. In support of this view, it has been shown that fish Mb O2 affinities differ between species when measured at the same temperature, but are in fact similar when adjusted for in vivo muscle temperatures, most likely to maintain intracellular O2 delivery in species adapted to different environments. It is unknown whether similar adaptations exist in the O2 affinity of Mb from reptiles, despite this group of ectothermic vertebrates displaying great variation in the tolerance to both temperature and hypoxia.