Washington, Dec 9 : A new study has suggested that Emperor penguins, the largest of all penguin species, manage to dive underwater for more than 20 minutes on a single breath because of a supercharged form of a blood protein in their body.
A new study has suggested that Emperor penguins, the largest of all penguin species, manage to dive underwater for more than 20 minutes on a single breath because of a supercharged form of a blood protein in their body.
The study revealed that penguins in Antarctica return from long fishing excursions under the sea ice with the lowest blood oxygen levels ever recorded in wild animals.
According to experts, with such depleted reserves, other creatures would collapse and suffer tissue damage.
The new finding has suggested that emperor penguins might have a hyped-up version of haemoglobin, the blood protein that carries oxygen from the lungs to the body.
Other species are unable to use all the oxygen in their lungs, even when starved for air, because their haemoglobin cannot efficiently bind with and carry oxygen in low concentrations. However, penguin haemoglobin appears to be extra-sensitive, scooping up the last remaining oxygen in the birds' air sacs and delivering it to vital organs.
"We hypothesize that the emperor can store more oxygen in its blood due to different binding properties of its haemoglobin. This would allow it to use its lung oxygen completely and would also provide a greater oxygen content at low oxygen pressures so that there is no tissue damage," National Geographic quoted the lead author Paul Ponganis of the Scripps Institution of Oceanography in San Diego, California, as saying.
Emperor penguins can manage to dive down to 1,850 feet (565 meters) while searching for fish, squid, and krill in the open ocean.
Such penguins have a variety of adaptations that help them enhance their ability to store oxygen and control its consumption rate.
For example, higher concentrations of haemoglobin and the blood protein myoglobin allow emperor penguins to store about 2.5 times more oxygen per unit of body mass than humans.
The birds also conserve oxygen by slowing their heart rate to as low as five beats a minute on long dives, even while chasing after fish.
"If we can understand why a diving animal does not incur tissue damage when exposed to low oxygen levels and low blood flow, [we may gain] a better understanding of how such damage occurs in humans and how it might be prevented," Ponganis said.
For the study, Ponganis and his colleagues monitored oxygen levels inside the blood vessels of wild birds living temporarily at the 'Penguin Ranch' research facility on McMurdo Sound in southern Antarctica.
The thick layer of sea ice on the ranch is broken only by diving holes drilled by scientists. Since the birds are too far away from other openings, they must return to the same location after fishing trips.
The study penguins were equipped with tiny sensors inside their air sacs. These sensors transmitted data to special recorders strapped to the birds' backs.
Most of the recorded dives were under six minutes long, but some were substantially longer, including a 23-minute descent that stands as the longest known emperor penguin dive.
David R. Jones, not involved in the penguin research, has studied the physiology of diving ducks at the University of British Columbia in Vancouver.
"I think it's just amazing that these animals are able to push themselves to such a degree that they use up virtually all of their oxygen stores in their respiratory system and blood. And the ability of Ponganis and colleagues to collect blood-oxygen data in the bitter cold of Antarctica is "amazing. This is a really important contribution to the field of diving physiology," Jones said.
The findings appear in the current issue of the Journal of Experimental Biology. (ANI)
© 2007 ANI
