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Why Don't Octopuses Get Stuck to Themselves?

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Life can't be easy for octopuses. Sure, they're universally loved for changing color, opening jars from the inside, and predicting the winners of World Cup games. But they have eight very flexible arms to keep track of, which aren't even under their full control. Each arm is fairly autonomous, and a lot of the motor control happens in the neural circuitry of the arms themselves instead of the brain.

Forget about the left hand not knowing what the right hand is doing. At any given moment, not a single octopus tentacle knows what the other seven are up to—and neither does the octopus.

Not only are these eight arms writhing around unhindered by elbows, wrists, or a central control system, but each one is also covered in hundreds of suckers that that will reflexively stick to just about anything. You would think that this would lead to octopuses getting tangled up in themselves pretty regularly, but it doesn't.

A new paper shows why: The one thing that the suckers don't stick to is the octopus' own skin.

For about an hour after amputation, an octopus arm pretty much acts as if it were still attached. It moves similarly, while the suckers grasp and stick to things they touch. In what must have looked like a darkly surreal experiment to anyone who stumbled upon it, a team of Israeli and American scientists observed what these flailing arms would and wouldn't grab.

In more than 30 trials, the researchers found that the suckers wouldn't attach to another octopus arm, whether it came from the same animal or a different one. Nor would they latch on to a petri dish that was covered in octopus skin.

They would grab another arm if it had been skinned, though. And if a petri dish was only partially covered, the suckers held the exposed plastic but avoided the skin.

It was starting to look like the skin made all the difference, so the researchers coated petri dishes in a gel that was soaked in dissolved chemicals extracted from the octopus skin. When they offered these to the amputated arms, the suckers grabbed them, but with 10 to 20 times less force than they did the regular, uncoated ones.

This confirmed that some chemical in the skin hinders the attachment reflex, thereby preventing the suckers from sticking. For the octopus, this means that each arm keeps the others from grabbing hold of it without the octopus having to worry about the details.

Interestingly, live octopuses have the ability to override the sucker-stopping signal when they want to. In another experiment, live animals showed they could grab amputated arms, but were less likely to do so if the arm had been one of their own. This suggests that they can tell their own limbs from another's. Furthermore, it's possible that their skin-recognition trick might involve the brain, and isn't limited to skin-sucker interactions.

Still, it's unclear which specific chemical prevents sucker attachment. Researchers think the mystery chemical probably acts on the chemical receptors in the individual suckers.

However it works, the self-avoidance system, the researchers say, is a "striking addition to the list of surprises" in the octopus' body. It not only keeps octopuses from tying themselves in knots, but also frees them up to do all the cool things we love them for.

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New Plankton Species Named After Sir David Attenborough Series Blue Planet
John Phillips, Getty Images for Tourism Australia
John Phillips, Getty Images for Tourism Australia

At least 19 creatures, both living and extinct, have been named after iconic British naturalist Sir David Attenborough. Now, for the first time, one of his documentary series will receive the same honor. As the BBC reports, a newly discovered phytoplankton shares its name with the award-winning BBC series Blue Planet.

The second half of the species' name, Syracosphaera azureaplaneta, is Latin for "blue planet," likely making it the first creature to derive its name from a television program. The single-cell organisms are just thousandths of a millimeter wide, thinner than a human hair, but their massive blooms on the ocean's surface can be seen from space. Called coccolithophores, the plankton serve as a food source for various marine life and are a vital marker scientists use to gauge the effects of climate change on the sea. The plankton's discovery, by researchers at University College London (UCL) and institutions in Spain and Japan, is detailed in a paper [PDF] published in the Journal of Nannoplankton Research.

"They are an essential element in the whole cycle of oxygen production and carbon dioxide and all the rest of it, and you mess about with this sort of thing, and the echoes and the reverberations and the consequences extend throughout the atmosphere," Attenborough said while accepting the honor at UCL.

The Blue Planet premiered in 2001 with eight episodes, each dedicated to a different part of the world's oceans. The series' success inspired a sequel series, Blue Planet II, that debuted on the BBC last year.

[h/t BBC]

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'Angry Badger' Terrorizes Scottish Castle, Forcing Closures 
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Portions of the 16th-century Craignethan Castle in Scotland were shut down last week after a less-than-friendly badger holed up there and refused to leave. Historic Environment Scotland, which manages the site in South Lanarkshire, sent out a tweet last Friday notifying visitors that the property's cellar tunnel would remain closed over the weekend “due to the presence of a very angry badger.” Staff tried to coax it out with cat food and honey, but the badger did what it wanted, and they were unable to move the mammal.

A spokesman for HES told the BBC, "The castle is surrounded by woodland and we believe the badger may have become lost. Staff first spotted some dug-out earth on Wednesday evening, and later spotted the badger on closer inspection."

On Saturday, staff used a GoPro camera to check out the tunnel from a safe distance and learned that the badger had left voluntarily, but not before making a mess. The critter dug through both soil and stonework, according to The Scotsman. The castle, an artillery fortification erected around 1530, is already partly in ruins.

Craignethan Castle in Scotland
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Badgers are not typically dangerous, but they can become aggressive if they feel cornered or threatened. They can be seen year-round in Scotland, especially during spring and summer. Earthworms, bird eggs, small mammals, fruit, and roots are among their favorite meals, and they can even be “tempted into your garden by leaving peanuts out—a tasty snack for our striped friends,” the Scottish Wildlife Trust says.

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