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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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These Deep-Sea Worms Could Live More Than a Thousand Years

Plunge below the sparkling surface of the Gulf of Mexico, head down into the depths, and there you'll find the ancient ones, growing in clusters of drab tubes like piles of construction equipment. Scientists writing in the journal The Science of Nature report that some of these worms could be more than 1000 years old.

When it comes to marine organisms, the deeper you go, the slower and older life gets. Biologists have found an octopus that guarded her eggs for four and a half years. They've seen clams born during the Ming dynasty and sharks older than the United States. They've seen communities of coral that have been around for millennia.

Previous studies have shown that some species of tube worm can live to be 250 years old. To find out if the same was true for other species—in this case, the Gulf of Mexico's Escarpia laminata—researchers spent years watching them grow. They used a long-lasting dye called Acid Blue to mark six clusters of worms, then let them to go about their wormy business. A year later, they collected all 356 blue-stained tubes and brought them back to the lab to measure their growth.

By calculating the speed of the worms' growth and comparing it to the size of the largest individuals, the scientists could devise a pretty good estimate of the oldest worms' age.

And boy, are they old. The researchers' worm-growth simulation suggested that the most ancient individuals could be more than 9000 years old. This seems incredible, even for tough old tube worms, so the scientists calculated a more conservative maximum age: a mere 1000 years.

A millennium-long lifespan is an extreme and not the average, the paper authors note. "There may indeed be large E. laminata over 1000 years old in nature, but given our research, we are more confident reporting a life span of at least 250 to 300 years," lead author Alanna Durkin of Temple University told New Scientist.

Still, Durkin says, "E. laminata is pushing the bounds of what we thought was possible for longevity."

She's excited by the prospect of finding older creatures yet.

"It's possible that new record-breaking life spans will be discovered in the deep sea,” she says, “since we are finding new species and new habitats almost every time we send down a submersible.”

 

[h/t New Scientist]

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Animals
Watch as Hummingbirds Fly, Drink, and Flap Their Tiny Wings in Slow Motion
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Hummingbirds have more feathers per inch than nearly any other bird, but it’s hard to fully appreciate their luminescent colors when they beat their wings between 70 to 200 times per second.

For the enjoyment of birders everywhere, National Geographic photographer Anand Varma teamed up with bird biologists and used a high-speed, high-resolution camera to capture the tiny creatures in slow motion as they flew through wind tunnels, drank artificial nectar from a glass vessel, and shook water from their magnificent plumage.

[h/t The Kid Should See This]

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