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article imageHow marine mammals hold their breath for long time underwater

By Eko Armunanto     Jun 22, 2013 in Science
Marine mammals like seals, dolphins and whales can stay underwater for long periods of time, even more than an hour, while humans can only do so for a few minutes at most.
A new study found special properties of an oxygen-binding protein in the muscles of marine mammals like seals, whales and dolphins, are the reason they can hold their breath underwater for long periods of time. Most of these divers can hold their breath underwater for over an hour, while land-based mammals like humans can only do so for a few minutes at most.
University of Liverpool’s scientists were able to identify a unique molecular characteristic of myoglobin, an iron and oxygen-binding protein found in sperm whales and other diving mammals. Very little was known, until this finding, about how the molecule is adapted in the diving marine mammals. Collaborating with the University of Manitoba and University of Alaska, the researchers found a high concentration of myoglobin, the substance that makes meat look red, in the muscles of the mammalian divers. The amount was so high in fact in the muscle that it almost looked black in color, therefore the scientists is now able to trace the evolution of how the muscles of more than 100 species of mammals, including fossil remains of their ancient predecessors, were able to store oxygen.
Published in Science Magazine, the scientists say high muscle myoglobin concentrations in particular are mechanistically linked with an extended dive capacity phenotype, yet little is known regarding the molecular and biochemical underpinnings of this key specialization. “We modeled the evolutionary history of this respiratory pigment over 200 million years of mammalian evolution to elucidate the development of maximal diving capacity during the major mammalian land-to-water transitions,” they say.
Marine mammals like common seals, for instance, are able to spend 80% of their time underwater. They can dive for about 30 minutes and even sleep underwater. Their nervous system has an automatic shut-off mechanism that prevents them from breathing at inappropriate times. Sperm whale is one of nature's best divers; these whales routinely dive for 45 minutes and to depths of more than one kilometer – enables them to hunt the giant squid they eat.
Researchers at the US-based Woods Hole Oceanographic Institution tracked Cuvier's beaked whales diving to nearly 2 kilometer and staying down for 85 minutes. This is one of 21 species in the beaked whale group. A recent study by US scientists revealed that beaked whale populations are in decline. Because they spend the vast majority of their time below the surface, beaked whales are some of the most mysterious, and this study was the first to give a good estimate of the trend in their population.
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