Kevin Struhl

Blood sampling catheters or oxygen electrodes were inserted into the aorta or vena cava of penguins under anaethesia. After recovery, the birds were allowed to dive through the isolated dive hole, which ensured that the birds returned to this hole. After one or two days of diving, the equipment was removed, data recorded and the birds allowed to recover. On analysis of the data from these dives, the researchers found that the penguins were capable of reaching extremely low levels of blood oxygen at the time of their return to the surface of the dive hole. The lowest of the air sac values was significant in relation to the results from other birds. The lowest values in emperor penguins are less than that in air breathed in by birds flying at altitudes of more than ,500 metres and lower than that found in birds flying at these high altitudes, such as the barheaded goose. The researchers found that the remarkably low levels of intervascular and air sac levels of oxygen in emperor penguins is achieved at least in part from the optimum management of oxygen reserves and extreme hypoxemic tolerance. In particular, the birds’ haemoglobin with high oxygen affinity enhanced blood oxygen content during hypoxemia and allowed the depletion of respiratory reserves. The oxygen levels were also extremely low by human comparison, even with patients undergoing treatment for hypoxemia and from climbers at the top of Mount Everest. As well as revealing a highly specialised mechanism by which emperor penguins can catch their food, the authors believe the novel physiological properties may also help to develop models for improved understanding and treatment of human hypoxemic and ischemic pathologies. Extreme: An emperor penguin begins a dive in which oxygen levels may reach extraordinarily low levels. (Photo: K. Ponganis.) Q & A