AN OXYGEN reservoir within seals' muscles could explain how they can dive underwater for up to 80 minutes at a time without taking a breath.
Seal muscle contains 20 times as much myoglobin--a protein that stores and transfers oxygen within their cells--as humans. Seals also stop breathing for 20 minutes at a time while asleep on land, which probably helps them conserve energy.
Thomas Jue of the University of California, Davis, and his team measured the levels of deoxygenated myoglobin in two elephant seals as they fell asleep. They found that as the animals fell into a slumber and stopped breathing, their blood flow slowed. "The metabolism drops," says Jue.
Oxygen levels in the seals' myoglobin fell by 20 per cent within the first minute of sleep, as the cells used up their oxygen stores. This freed myoglobin to pull more oxygen from the blood, stabilising the cells' oxygen level until the seals started breathing again (Journal of Experimental Biology, DOI: 10.1242/jeb.025130).
Jue admits that the animals might use oxygen differently while diving but says this method is better than forcibly immersing seals in water, whereby "the animal exhibits the physiology of panic".
Source Citation:"Seals have scuba tank built in.(Brief article)." New Scientist 200.2677 (Oct 11, 2008): 16(1). InfoTrac Information Science & Library Issues eCollection. Gale. BROWARD COUNTY LIBRARY. 16 May 2009
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