The mighty water bear is not a handsome dude. (AMNH)

When we talk about 'extreme' animals, the tardigrade easily takes the cake: Also known as the water bear, the tardigrade is a microscopic critter (just 1.5 mm across, at most!) that can withstand just about anything. So it's no surprise that the water bear is the clear star of the American Natural History Museum's latest exhibit, "Life at the Limits."

[The platypus is so weird that scientists thought the first specimen was a hoax]

The exhibit, open from April 4 until Jan. 3, features a whole host of other plants, animals, bacteria, and fungi that dive the deepest, live the longest, and in the weirdest conditions. When I visited a few days before the opening, I got to sniff a flower that mimics rotting flesh to attract insects (conclusion: smell it once for science, then never again), learn about everything from deep-diving manatees to weight-lifting beetles, and meet a living mantis shrimp, the species famous for seeing in a level of technicolor we can't even comprehend with our puny human brains. Here are some highlights from the day, which I shared with our Snapchat followers:



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So yes, there are a ton of thrillingly weird and wild creatures to gawk at in the new exhibit. But when you enter the space, the mood is set by a gang of blown-up tardigrades hanging from the ceiling. The message is clear: These tiny little nightmare monsters are the most extreme of the extreme.

[The ‘termites of the sea’ have super weird digestive systems, and they might help us make biofuels]

Also, this is in the gift shop:


Here's the deal: Tardigrades were first spotted as "animalcules" (which is one of my favorite defunct science words) by Antonie van Leeuwenhoek (a.k.a the father of microbiology) when he added water to dust from the gutter in 1702. About 70 years later, they were classified as a new species after being spotted in the same way -- seemingly rising from the dead, emerging from lifeless dust to scurry around under the microscope.

Since then, scientists have revealed more and more of the superpowers these water-dwelling animals  possess: They can actually survive all dried out for years before getting rehydrated (which is especially intriguing when you consider that their lifespans while active are only a few months), and one scientist even claimed to rehydrate 120-year-old specimens. From the BBC:

Shedding almost all the water in its body, the tardigrade curls up into a dry husk. Baumann called this a "Tönnchenform", but it is now commonly known as a "tun". Its metabolism slows to 0.01% of the normal rate. It can stay in this state for decades, only reanimating when it comes into contact with water.

That's not all the water bear has up its itty bitty sleeves.

It turns out that this adaptation to survive drought also allows it to survive naked in space. A 2007 study found that most tardigrades could survive the vacuum of space if they were shielded from the sun's incredible radiation levels -- and most of them went on to lay healthy eggs after being revived. Fewer water bears survived when left totally exposed to space radiation, but a handful of them managed it. So far, they're the only animal to do so.

From Popular Mechanics:

According to Peter Guida, the head of NASA's space radiation laboratory, one of the biggest radiation concerns for astronauts (and space-bound tardigrades) is a set of molecules called reactive oxygen species. Ionizing radiation enters the body and bores into wayward molecules that contain oxygen. In simple terms, those newly irradiated molecules then troll through the body causing all sorts of harm.

Tardigrades during their desiccated state produce an abnormal amount of anti-oxidants (yes, these actually exist outside the health-food world), which effectively neutralize those roaming, evil reactive oxygen species. Partly because of this talent, tardigrades have been found to withstand higher radiation doses with far greater success than researchers would otherwise believe they should.


(AMNH)

Tardigrades aren't just weird and cool. They're also really important in our hunt for extraterrestrial life. Animals like the tardigrade turn our notion of "life as we know it" right on its head then spin it around 180 degrees for good measure. It's becoming increasingly clear that "life" may not always be the way we "know" it to be. When we find it on another planet, we might realize we haven't even been looking for the right things. These extreme creatures stretch the limits of what we know is possible, allowing us to stretch our imaginations even further.

You can find out more about water bears and other incredibly extreme earthlings at AMNH. And you can do it surrounded by giant, floating water bears, which is how it should be.

Correction: A previous version of this post referred to water bears as members of the phylum rotifer, but water bears are actually a separate phylum (tardigrade). 

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