ISTOCK
ISTOCK

Water Bear Genome Reveals Even More Weirdness

ISTOCK
ISTOCK

We see a lot of weird animals here, but the tardigrade continually takes the cake. The tardigrade, commonly known as a water bear or a moss piglet, has captivated researchers for two centuries with its freakish near-invincibility. Scientists recently sequenced the genome of one tardigrade species, hoping to find some answers. Instead, they found more strangeness: It turns out that tardigrades can borrow genes from bacteria, fungi, and even plants. The researchers' findings were recently published in the Proceedings of the National Academy of Sciences

There are more than 1000 tardigrade species, all of which are pudgy, microscopic, and unbelievably hardy. Experiments have shown that tardigrades can survive temperatures below -458°F and above 300°F. You can zap them with radiation, take away their food and water, even leave them in the vacuum of space—and they’ll be just fine. When the going gets tough, tardigrades simply go into a state of suspended animation called cryptobiosis. Their metabolisms slow to almost nothing, and they dry up into little barrel-shaped husks called tuns. They won’t come out until the coast is clear. 

Lots of animals hibernate, and plenty of others enter cryptobiosis. But no other animals can do what the tardigrades do.

For all their toughness, tardigrades are pretty hard to keep alive in the lab. The Goldstein lab at UNC Chapel Hill is one of the few places in the world that has figured it out. Some tardigrade species are more cooperative than others, so when researcher Thomas Boothby decided to sequence a tardigrade genome, he picked the easygoing species Hypsibius dujardini.

True to tardigrade form, the results were super, super weird. Boothby and his colleagues found that the moss piglet’s DNA contained scraps of genes copied and pasted from other organisms. The genes weren’t taken from other animals, either—they came from plants, and fungi, and bacteria. 

This liberal use of other organisms' genes is made possible through a rare (and even disputed) phenomenon known as horizontal gene transfer (HGT). As Ed Yong notes in the Atlantic, ticks, wasps, aphids, and fruit flies have all been caught swiping genes from fungi, bacteria, and viruses.

But these species only take one or two genes, which can make up about 1 percent of their DNA. Not so with H. dujardini. Boothby and his team found that stray genes from foreign species make up 17.5 percent, or a whopping one-sixth, of the tardigrade’s genome. About 90 percent come from diverse bacteria. “The number of them is pretty staggering,” he told Yong. 

Not everybody buys into the HGT phenomenon, and some previous examples have since been debunked as contaminated specimens. (If any trace of another species gets into a sample, the DNA of both species will show up in tests.)

The UNC researchers wanted to be extra sure before they published their results, so they double-checked the genome using a system called PacBio, which analyzes single unbroken strands of DNA, as Yong describes. The PacBio analysis confirmed it: Those genes all belonged to the tardigrade. The foreign strands of DNA were so interwoven with the tardigrade’s that some of the nonanimal genes had taken on animal traits.

This is highly unusual, to put it mildly. Boothby believes the secret lies in the tardigrade’s curl-up-and-fake-death response to difficult conditions. “So we think tardigrades are drying out, and their DNA is fragmenting along with the DNA of bacteria and organisms in the environment,” Boothby said in the Atlantic. “That gets into their cells when they rehydrate. And when they stitch their own genomes together, they may accidentally put in a bacterial gene.” 

Those genes may be the key to the water bear’s invincibility. Boothby and his colleagues have already found that tardigrades switch on some of these genes in response to stress. If a tardigrade accidentally picks up genes that happen to make it tougher or more adaptable, it’s probably going to keep them. 

The research team plans to peer next into the genes of other animals. What’s true for the tardigrade may be true for other species—some of it, anyway. One thing's for sure: The deeper we go into tardigrade biology, the more bizarre it gets.

nextArticle.image_alt|e
iStock
arrow
Animals
How Bats Protect Rare Books at This Portuguese Library
iStock
iStock

Visit the Joanina Library at the University of Coimbra in Portugal at night and you might think the building has a bat problem. It's true that common pipistrelle bats live there, occupying the space behind the bookshelves by day and swooping beneath the arched ceilings and in and out of windows once the sun goes down, but they're not a problem. As Smithsonian reports, the bats play a vital role in preserving the institution's manuscripts, so librarians are in no hurry to get rid of them.

The bats that live in the library don't damage the books and, because they're nocturnal, they usually don't bother the human guests. The much bigger danger to the collection is the insect population. Many bug species are known to gnaw on paper, which could be disastrous for the library's rare items that date from before the 19th century. The bats act as a natural form of pest control: At night, they feast on the insects that would otherwise feast on library books.

The Joanina Library is famous for being one of the most architecturally stunning libraries on earth. It was constructed before 1725, but when exactly the bats arrived is unknown. Librarians can say for sure they've been flapping around the halls since at least the 1800s.

Though bats have no reason to go after the materials, there is one threat they pose to the interior: falling feces. Librarians protect against this by covering their 18th-century tables with fabric made from animal skin at night and cleaning the floors of guano every morning.

[h/t Smithsonian]

nextArticle.image_alt|e
iStock
arrow
Animals
Honey Bees Can Understand the Concept of Zero
iStock
iStock

The concept of zero—less than one, nothing, nada—is deceptively complex. The first placeholder zero dates back to around 300 BCE, and the notion didn’t make its way to Western Europe until the 12th century. It takes children until preschool to wrap their brains around the concept. But scientists in Australia recently discovered a new animal capable of understanding zero: the honey bee. According to Vox, a new study finds that the insects can be taught the concept of nothing.

A few other animals can understand zero, according to current research. Dolphins, parrots, and monkeys can all understand the difference between something and nothing, but honey bees are the first insects proven to be able to do it.

The new study, published in the journal Science, finds that honey bees can rank quantities based on “greater than” and “less than,” and can understand that nothing is less than one.

Left: A photo of a bee choosing between images with black dots on them. Right: an illustration of a bee choosing the image with fewer dots
© Scarlett Howard & Aurore Avarguès-Weber

The researchers trained bees to identify images in the lab that showed the fewest number of elements (in this case, dots). If they chose the image with the fewest circles from a set, they received sweetened water, whereas if they chose another image, they received bitter quinine.

Once the insects got that concept down, the researchers introduced another challenge: The bees had to choose between a blank image and one with dots on it. More than 60 percent of the time, the insects were successfully able to extrapolate that if they needed to choose the fewest dots between an image with a few dots and an image with no dots at all, no dots was the correct answer. They could grasp the concept that nothing can still be a numerical quantity.

It’s not entirely surprising that bees are capable of such feats of intelligence. We already know that they can count, teach each other skills, communicate via the “waggle dance,” and think abstractly. This is just more evidence that bees are strikingly intelligent creatures, despite the fact that their insect brains look nothing like our own.

Considering how far apart bees and primates are on the evolutionary tree, and how different their brains are from ours—they have fewer than 1 million neurons, while we have about 86 billion—this finding raises a lot of new questions about the neural basis of understanding numbers, and will no doubt lead to further research on how the brain processes concepts like zero.

[h/t Vox]

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios