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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
Australian Charity Releases Album of Cat-Themed Ballads to Promote Feline Welfare
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An Australian animal charity is helping save the nation’s kitties one torch song at a time, releasing a feline-focused musical album that educates pet owners about how to properly care for their cats.

Around 35,000 cats end up in pounds, shelters, and rescue programs every year in the Australian state of New South Wales, according to the Royal Society for the Prevention of Cruelty to Animals (RSPCA). Microchipping and fixing cats, along with keeping closer tabs on them, could help reduce this number. To get this message out, the RSPCA’s New South Wales chapter created Cat Ballads: Music To Improve The Lives Of Cats.

The five-track recording is campy and fur-filled, with titles like "Desex Me Before I Do Something Crazy" and "Meow Meow." But songs like “I Need You” might tug the heartstrings of ailurophiles with lyrics like “I guess that’s goodbye then/but you’ve done this before/the window's wide open/and so’s the back door/you might think I’m independent/but you’d be wrong.” There's also a special version of the song that's specifically designed for cats’ ears, featuring purring, bird tweets, and other feline-friendly noises.

Together, the tunes remind us how vulnerable our kitties really are, and provide a timely reminder for cat owners to be responsible parents to their furry friends.

“The Cat Ballads campaign coincides with kitten season, which is when our shelters receive a significantly higher number of unwanted kittens as the seasons change,” Dr. Jade Norris, a veterinary scientist with the RSPCA, tells Mental Floss. “Desexing cats is a critical strategy to reduce unwanted kittens.”

Listen to a song from Cat Ballads below, and visit the project’s website for the full rundown.

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Animals
Scientists Discover 'Octlantis,' a Bustling Octopus City
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Sylke Rohrlach, Wikimedia Commons // CC BY-SA 4.0

Octopuses are insanely talented: They’ve been observed building forts, playing games, and even walking on dry land. But one area where the cephalopods come up short is in the social department. At least that’s what marine biologists used to believe. Now a newly discovered underwater community, dubbed Octlantis, is prompting scientists to call their characterization of octopuses as loners into question.

As Quartz reports, the so-called octopus city is located in Jervis Bay off Australia’s east coast. The patch of seafloor is populated by as many as 15 gloomy octopuses, a.k.a. common Sydney octopuses (octopus tetricus). Previous observations of the creatures led scientists to think they were strictly solitary, not counting their yearly mating rituals. But in Octlantis, octopuses communicate by changing colors, evict each other from dens, and live side by side. In addition to interacting with their neighbors, the gloomy octopuses have helped build the infrastructure of the city itself. On top of the rock formation they call home, they’ve stored mounds of clam and scallop shells and shaped them into shelters.

There is one other known gloomy octopus community similar to this one, and it may help scientists understand how and why they form. The original site, called Octopolis, was discovered in the same bay in 2009. Unlike Octlantis, Octopolis was centered around a manmade object that had sunk to the seabed and provided dens for up to 16 octopuses at a time. The researchers studying it had assumed it was a freak occurrence. But this new city, built around a natural habitat, shows that gloomy octopuses in the area may be evolving to be more social.

If that's the case, it's unclear why such octo-cities are so uncommon. "Relative to the more typical solitary life, the costs and benefits of living in aggregations and investing in interactions remain to be documented," the researchers who discovered the group wrote in a paper published in Marine and Freshwater Behavior and Physiology [PDF].

It’s also possible that for the first time in history humans have the resources to see octopus villages that perhaps have always been bustling beneath the sea surface.

[h/t Quartz]

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