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How Do Whales Hold Their Breath for Such a Long Time?

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By Chris Gayomali

Marine mammals have all kinds of wonderful adaptations to lead a comfortable life underwater, such as flippers and insulating blubber. Whales even have eyes that can see in monochrome, which is especially valuable deep beneath the surface where sunlight is at a premium.

But one of the whales' more fascinating adaptations is their enviable ability to hold their breath underwater for up to an hour at a time. Scientists know it has something to do with their myoglobin, a molecule in the blood that helps the body's muscles retain oxygen. In creatures like cows and humans, myoglobin is known for giving flesh its reddish tinge; seals and whales, on the other hand, have extremely high myoglobin concentrations that make their tissue look black.

Researcher Michael Berenbrink, a zoologist at the University of Liverpool, thought that was peculiar. "At high enough concentrations, [proteins] tend to stick together," Berenbrink tells BBC News. When too many proteins clump together, they become useless—dead weight.

So just how do densely packed myoglobin molecules in aquatic mammals keep from sticking together? BBC News reports:

The team extracted pure myoglobin from the muscles of mammals—from the land-based cow, to the semi-aquatic otter, all the way up elite divers like the sperm whale.

Led by researcher Scott Mirceta, this painstaking examination traced the changes in myoglobin in deep-diving mammals through 200 million years of evolutionary history.

And it revealed that the best mammalian breath-holding divers had evolved a non-stick variety of myoglobin. [BBC News]

The trick, apparently, is that the myoglobin of marine animals is positively charged, like one end of a magnet. Instead of clumping together, the molecules repel one another away, ensuring the blood stays loose and lubricated.

The whale's ability to hold its breath is, in a way, an evolutionary one-two punch: (1) The high concentration of myoglobin allows it to spend more time underwater in between breaths, and (2) the myoglobin's positive charge ensures the proteins don't clump together and kill the animal. Researchers say that mimicking this natural chemistry could have an impact in medical science, particularly in the way we perform human blood transfusions.

Berenbrink and his team even went so far as to reconstruct the myoglobin sequences of the whale's ancestors to pinpoint when the evolutionary adaptation may have occurred. "If you give me a myoglobin sequence, I can tell you if the animal is a good diver or not," says Berenbrink. Nature explains:

Using the reconstructed sequences from different animals to infer the electric charge on their myoglobin, together with information about the animal's body mass, the team was able to determine that an early whale ancestor—the terrestrial, wolf-sized animal Pakicetus—couldn't stay under water for much more than 90 seconds. But the larger, six-ton Basilosaurus, which appeared about 15 million years later than Pakicetus, could manage about 17 minutes. Many modern whales can remain submerged for more than an hour. [Nature]

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Big Questions
What Makes a Cat's Tail Puff Up When It's Scared?
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Cats wear their emotions on their tails, not their sleeves. They tap their fluffy rear appendages during relaxing naps, thrash them while tense, and hold them stiff and aloft when they’re feeling aggressive, among other behaviors. And in some scary situations (like, say, being surprised by a cucumber), a cat’s tail will actually expand, puffing up to nearly twice its volume as its owner hisses, arches its back, and flattens its ears. What does a super-sized tail signify, and how does it occur naturally without help from hairspray?

Cats with puffed tails are “basically trying to make themselves look as big as possible, and that’s because they detect a threat in the environment," Dr. Mikel Delgado, a certified cat behavior consultant who studied animal behavior and human-pet relationships as a PhD student at the University of California, Berkeley, tells Mental Floss. The “threat” in question can be as major as an approaching dog or as minor as an unexpected noise. Even if a cat isn't technically in any real danger, it's still biologically wired to spring to the offensive at a moment’s notice, as it's "not quite at the top of the food chain,” Delgado says. And a big tail is reflexive feline body language for “I’m big and scary, and you wouldn't want to mess with me,” she adds.

A cat’s tail puffs when muscles in its skin (where the hair base is) contract in response to hormone signals from the stress/fight or flight system, or sympathetic nervous system. Occasionally, the hairs on a cat’s back will also puff up along with the tail. That said, not all cats swell up when a startling situation strikes. “I’ve seen some cats that seem unflappable, and they never get poofed up,” Delgado says. “My cats get puffed up pretty easily.”

In addition to cats, other animals also experience piloerection, as this phenomenon is technically called. For example, “some birds puff up when they're encountering an enemy or a threat,” Delgado says. “I think it is a universal response among animals to try to get themselves out of a [potentially dangerous] situation. Really, the idea is that you don't have to fight because if you fight, you might lose an ear or you might get an injury that could be fatal. For most animals, they’re trying to figure out how to scare another animal off without actually going fisticuffs.” In other words, hiss softly, but carry a big tail.

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What Happened to the Physical Copy of the 'I Have a Dream' Speech?
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AFP, Getty Images

On August 28, 1963, Martin Luther King Jr. stood on the steps of the Lincoln Memorial and gave a speech for the ages, delivering the oratorical masterpiece "I Have a Dream" to nearly 250,000 people.

When he was done, King stepped away from the podium, folded his speech, and found himself standing in front of George Raveling, a former Villanova basketball player who, along with his friend Warren Wilson, had been asked to provide extra security around Dr. King while he was speaking. "We were both tall, gangly guys," Raveling told TIME in 2003. "We didn't know what we were doing but we certainly made for a good appearance."

Moved by the speech, Raveling saw the folded papers in King’s hands and asked if he could have them. King gave the young volunteer the speech without hesitation, and that was that.

“At no time do I remember thinking, ‘Wow, we got this historic document,’” Raveling told Sports Illustrated in 2015. Not realizing he was holding what would become an important piece of history in his hands, Raveling went home and stuck the three sheets of paper into a Harry Truman biography for safekeeping. They sat there for nearly two decades while Raveling developed an impressive career coaching NCAA men’s basketball.

In 1984, he had recently taken over as the head coach at the University of Iowa and was chatting with Bob Denney of the Cedar Rapids Gazette when Denney brought up the March on Washington. That's when Raveling dropped the bomb: “You know, I’ve got a copy of that speech," he said, and dug it out of the Truman book. After writing an article about Raveling's connection, the reporter had the speech professionally framed for the coach.

Though he displayed the framed speech in his house for a few years, Raveling began to realize the value of the piece and moved it to a bank vault in Los Angeles. Though he has received offers for King’s speech—one collector wanted to purchase the speech for $3 million in 2014—Raveling has turned them all down. He has been in talks with various museums and universities and hopes to put the speech on display in the future, but for now, he cherishes having it in his possession.

“That to me is something I’ll always be able to look back and say I was there,” Raveling said in the original Cedar Rapids Gazette article. “And not only out there in that arena of people, but to be within touching distance of him. That’s like when you’re 80 or 90 years old you can look back and say ‘I was in touching distance of Abraham Lincoln when he made the Gettysburg Address.’"

“I have no idea why I even asked him for the speech,” Raveling, now CEO of Coaching for Success, has said. “But I’m sure glad that I did.”

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