Oxygen Mystery: How Can Marine Mammals Hold Their Breath For So Long Underwater? [STUDY]

By iScienceTimes Staff on June 14, 2013 3:28 PM EDT

sea otter
New research shows how marine mammals, as well as semi-aquatic mammals like otters, are able to stay underwater for so long without coming up for air. (Photo: Fotopedia: blazouf)

It's a question that has long puzzled scientists: If human beings can only last a few minutes underwater, how can some mammals last almost an hour? Now a team of scientists say they have figured out how marine mammals are able to spend so much time underwater without surfacing for air.

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In a new study, scientists from the University of Liverpool say that the key to marine mammals holding their breath underwater is myoglobin. The protein, which gives meat its red color, acts as an oxygen reserve in the blood. It's found in humans, but is present in much higher concentrations in marine mammals like sperm whales, and even in semi-aquatic animals like sea otters.

But proteins in high concentrations tend to stick together, impairing their function, so it wasn't clear how high concentrations of myoglobin would be a helpful in allowing animals to say underwater for long periods of time.   

"We studied the electrical charge on the surface of myoglobin and found that it increased in mammals that can dive underwater for long periods of time," said Michael Berenbrink of the University of Liverpool.

It turned out that it is the electrical charge on the surface of myoglobin that keeps the proteins from sticking to one another, which would impair their function.

As Scott Mirceta, a PhD student who worked on the project, explained it, "Our study suggests that the increased electrical charge of myoglobin in mammals that have high concentrations of this protein causes electro-repulsion, like similar poles of two magnets. This should prevent the proteins from sticking together and allow much higher concentrations of the oxygen-storing myoglobin in the muscles of these divers."

The scientists say that this new research was informative not only when it comes to modern mammals, but about how the diving mechanisms in marine mammals evolved.

"By mapping this molecular signature onto the family tree of mammals, we were able to reconstruct the muscle oxygen stores in extinct ancestors of today's diving mammals," said Berenbrink. "We were even able to report the first evidence of a common amphibious ancestor of modern sea cows, hyraxes and elephants that lived in shallow African waters some 65 million years ago."

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