Study reveals mystery of diving mammals' underwater endurance

WASHINGTON, June 14 (Xinhua) -- Diving mammals, such as the sperm whale, have a special oxygen-storing protein that lets them hold their breaths for long periods underwater, according to a study released Friday in the journal Science.

Researchers at the University of Liverpool identified a distinctive molecular signature of myoglobin, the oxygen-binding protein that gives meat its red color, in the sperm whale and other diving mammals. Concentrations of myoglobin in elite diving mammals are so high that the muscle is almost black, rather than red, in color.

According to the researchers, proteins tend to stick together at high concentrations, impairing their function, so it was unclear how this molecule is adapted in champion divers.

Elite mammalian divers can hold their breath for over an hour while they hunt in the depths of the oceans, while land mammals, such as humans, can hold their breath for only a few minutes.

In a bid to solve the mystery, the researchers 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.

"We were surprised when we saw the same molecular signature in whales and seals, but also in semi-aquatic beavers, muskrats and even water shrews," Michael Berenbrink, the study's lead author, said in a statement.