Newly Discovered Tardigrade Species Is Not Cute

Not all water bears are created equal.

Kazuharu Arakawa/YouTube

The darling of the microscopic world is the tardigrade, a hardy little microbe that’s so tiny it’s invisible to the naked eye. Nicknamed the “water bear,” this minuscule metazoan can survive some of the harshest climates in our universe, like deep oceans, red-hot geothermal vents, and even the walls of space-bound rockets. But that’s not why humans like them so much. We love them because, up close, the tardigrades we’re familiar with are plump, doughy, and altogether very cute.

But tardigrades are not a species but rather an entire family of organisms, and not all of its members evolved such pleasing aesthetics. On Wednesday, in the journal PLoS One, researchers led by Daniel Stec, Ph.D., from the Jagiellonian University in Poland report the discovery of Macrobiotus shonaicus sp. nov., a newly discovered species of tardigrade.

In this video uploaded by study co-author and Keio University biologist Kazuharu Arakawa, Ph.D., one can’t help but notice this tardigrade is not as cute. If the tardigrades we’re used to seeing look like little water bears, this one looks like a mid-length water bear turd with legs or a small, impaired platypus … if you’re feeling generous.

Alas, like humans among all the great apes, not all tardigrade species can be so lovable. The tardigrade type you’ve probably cooed over is the eutardigrada, images of which are commonly used as visual shorthand for the tardigrade class as a whole. Indeed, close-up shots of eutardigrades themselves, a subclass of over 700 species, make them seem quite cute.

But there are many species of tardigrades, found all over the world and probably beyond. The new species, M. shonaicus sp. nov., is actually one of 168 known tardigrade species in Japan alone.

The researchers found this aesthetically impaired little guy in a similarly homely place: a scoop of moss from a car park in Tsuruoka-City, Japan, where Arakawa rented an apartment nearby (“specific permission was not required,” the authors note). Using phase contrast light microscopy and scanning electron microscopy, they snapped close-up shots of the new species, revealing a scary mouth, scary claws, and really scary eggs.

Here it is in its entirety, looking rather bland:

Kind of leech-like, if you ask me. 

Stec et al.

Here’s its scary mouth:

M. shonaicus's freaky mouth.

Stec et al.

Here are its freaky claws:


Stec et al.

The eggs are the pièce de résistance. Close up, they’ve got a bulbous middle that narrows into a floppy opening crowned with wild, ragged filaments. They do not look unlike a ripe pimple caught mid-pop.

See? Not cute.

Stec et al (2018)

These scary eggs, however, were key to the organism’s classification as a new species. Though the organism as a whole is most similar to M. anemone from the United States, M. naskreckii from Mozambique, and M. patagonicus from Argentina, the researchers determined that M. shonaicus’ eggs put it into a class of its own.

“[It] can be easily distinguished from these species by the presence of thin flexible filaments on terminal discs of the egg process,” they write, describing the flailing, itchy-looking things in the image above. The eggs, furthermore, have a solid, poreless surface, putting them in a subclass known as the persimilis. The new classification is as follows:

Despite itself, M. shonaicus has earned its place on the tardigrade family tree.

Stec et al.

In the biological world, it’s not easy to earn your place as a unique species with its own classification. Perhaps it’s for the best, then, that M. shonaicus has so many, uh, unique features, even though its overall appearance leaves much to be desired.

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