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Courtesy of Oliver Lucanus

The Fierce Rapids of the Congo River Create New Fish Species

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Courtesy of Oliver Lucanus

Scientists say the turbulent waters of the lower Congo River divided one fish family so thoroughly that it split into several different species. The researchers published their findings in the journal Molecular Ecology.

One 200-mile stretch of the river has a peculiar claim to fame—it’s become a sort of evolutionary playground, boasting more than 300 different species of fish alone. “In this very short section of the Congo, we find a tremendous diversity of fishes,” co-author Melanie Stiassny of the American Museum of Natural History said in a statement.

At a mere 3 to 5 million years old, Stiassny said, this segment of the river is still relatively young. “So what is it about this system that makes it such a pump for species?”

New species are formed when an existing species is split into two populations, often by some sort of insurmountable physical barrier. Over thousands of years, the different environments and pressures faced by the two populations will be so different that they’ll evolve into two separate species.

But there are currently no major dams in this section of the Congo, nor does the river branch or trickle off into lakes. The fish are all essentially swimming in the same body of water.

Stiassny and her colleagues had a theory: The behavior of the water itself had broken fish families apart. To test their hypothesis, they collected 53 fish, all members of the genus Teleogramma, from different sections of the strange 200-mile stretch. The researchers sequenced the fishes’ DNA and compared their bodies, looking for similarities and differences.

There were plenty of differences. Within those 53 fish the researchers had representatives of all five Teleogramma species [PDF]. But some of those species were practically living on top of one another—sometimes less than a mile apart. But there was always something between them: roiling river rapids.

Alter et al. 2017. Molecular Genetics.

Lead author Elizabeth Alter, of CUNY York College and AMNH, said the rapids are working the same way a wall or a mountain might, keeping the fish populations separate. “What's particularly unique about the lower Congo is that this diversification is happening over extremely small spatial scales,” she said in the statement. “There is no other river like it.”

The fish may be facing even greater barriers in the near future, as the region has been proposed as the site of a new dam—a situation that Stiassny says would "majorly disrupt" this extraordinary ecosystem.

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Animals
25 Shelter Dogs Who Made It Big
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Focus Features

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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iStock

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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