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South American Earthworms Build Enormous Mounds of Poop

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Just when you think nature has maxed out on weird phenomena, here come the poop-piling worms of South America. Researchers say enormous earthworms are likely responsible for the huge mounds covering tens of thousands of square miles in the wetlands of Columbia and Venezuela. The scientists published their report in the journal PLOS One.

Those mounds are called surales. These broad green lumps on the landscape can reach more than 16 feet across. There are scores of them, patterning the wetlands like huge green polka dots. There are several types of patterned landscapes, the authors note in their paper, but surales “… must be seen to be believed.” Yet somehow these mysterious mounds have lain largely overlooked and uninvestigated.

Aerial view of surales landscape. Image credit: Delphine Renard

There are two primary theories about the mounds’ formation. One is that they were built by the movements of small animals, insects, or worms; and the other is that they’re the natural product of erosion around circles of plant roots. “Why the plants are regularly spaced has not been addressed in these cases,” write the authors of the current paper. “In addition, we found no authoritative source that demonstrates this phenomenon or even offers an explanation of how it could work.” In other words, they weren't buying it.

Residents of the Orinoco plains are pretty sure worms were responsible, and their names for the mounds (tatuco, zuro, zural, and sural) all refer to piles of worm poop. This is less outrageous than it might sound. Earthworms are plentiful on the plains, and some of them are gargantuan. The researchers decided to figure out if earthworms were making the mounds, and, if so, which earthworms.

The scientists went at the question from all angles, taking samples of plants, soil, stone, and worms, and scanning the landscape using images from aerial drones and Google Earth.

The combination of micro- and macro-level analysis revealed some answers—and some surprises. "We were really impressed not only by the regularity in the size and spacing of mounds in surales landscapes, but also by their spatial extent,” co-author Anne Zangerlé of Technische Universität Braunschweig said in a press statement. “We showed that they occur throughout much of the Orinoco Llanos, in both Colombia and Venezuela, but they have hardly been noticed by ecologists. We were surprised to find that the main driver of these earth-mound landscapes appears to be a single very large earthworm species."

When Zangerlé says “very large,” she’s not kidding. Juvenile Andiorrhinus sp. earthworms can reach more than 3 feet long. There are also a lot of them: This single species makes up for 92.9 percent of local earthworm biomass. They’re kind of in charge. 

To make the mounds, these big, juicy worms (or “soil engineers,” as the researchers call them) suck in muddy wetlands water, process the soil, and then poop it out in dry, hardened towers called castings. Those towers are not just for show; the worms climb up them to get out of the water and breathe. The castings pile up, and they combine to form the once-mysterious mounds.

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Animals
25 Shelter Dogs Who Made It Big
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If you’ve been thinking of adding a four-legged friend to your brood and are deciding whether a shelter dog is right for you, consider this: Some of history’s most amazing pooches—from four-legged movie stars to heroic rescue dogs—were found in animal shelters. In honor of Adopt-a-Shelter-Dog Month, here are 25 shelter dogs who made it big.

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This High-Tech Material Can Change Shape Like an Octopus
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Octopuses can do some pretty amazing things with their skin, like “see” light, resist the pull of their own sticky suction cups, and blend in seamlessly with their surroundings. That last part now has the U.S. Army interested, as Co.Design reports. The military branch’s research office has funded the development a new type of morphing material that works like an octopus’s dynamic skin.

The skin of an octopus is covered in small, muscular bumps called papillae that allow them to change textures in a fraction of a second. Using this mechanism, octopuses can mimic coral, rocks, and even other animals. The new government-funded research—conducted by scientists at Cornell University—produced a device that works using a similar principle.

“Technologies that use stretchable materials are increasingly important, yet we are unable to control how they stretch with much more sophistication than inflating balloons,” the scientists write in their study, recently published in the journal Science. “Nature, however, demonstrates remarkable control of stretchable surfaces.”

The membrane of the stretchy, silicone material lays flat most of the time, but when it’s inflated with air, it can morph to form almost any 3D shape. So far, the technology has been used to imitate rocks and plants.

You can see the synthetic skin transform from a two-dimensional pad to 3D models of objects in the video below:

It’s easy to see how this feature could be used in military gear. A soldier’s suit made from material like this could theoretically provide custom camouflage for any environment in an instant. Like a lot of military technology, it could also be useful in civilian life down the road. Co.Design writer Jesus Diaz brings up examples like buttons that appear on a car's dashboard only when you need them, or a mixing bowl that rises from the surface of the kitchen counter while you're cooking.

Even if we can mimic the camouflage capabilities of cephalopods, though, other impressive superpowers, like controlling thousands of powerful suction cups or squeezing through spaces the size of a cherry tomato, are still the sole domain of the octopus. For now.

[h/t Co.Design]

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