These tiny creatures can withstand more hardship than any other animal on the planet, and you can probably find some in your backyard. They are truly nature’s greatest survivors.
Tardigrades (Known as water bears or moss piglets) are some of the most interesting animals in the world, simply because they can survive so well in the most extreme conditions.
Tardigrades are nature’s ultimate survivors. As five-time mass extinction champions, they are the terrestrial organism most likely to survive in space, even beating the hated cockroach in the Animal Planet most extreme survivor award. These slow-moving moss piglets (their phylum Tardigrada, literally means slow steppers) had already been around 270 million years before the first tyrannosaurus rex made an appearance, and, if history is any indication, will far outlive any animal currently on the planet today. Known most commonly as “water bears,” these microscopic invertebrates are smaller than a single grain of sand. Recently they have made headlines as our first, albeit accidental, earthling to colonize the moon.
But why do scientists care about them so much anyway?
Water bears, nicknamed for their resemblance to a sort of eight-legged panda, are one of the most distinct members of the animal kingdom. Despite their small size, they have a full brain and nervous system, as well as a shell-like cuticle that they must shed in order to grow. Like everything else in their life, their cells divide very slowly, leading some early scientists to believe that tardigrades were eutelic, meaning that tardigrades would have the same number of cells in their bodies no matter the stage development. While research showed this wasn’t the case, tardigrades remained an organism of significant interest for another reason: their ability to survive some of the most extreme environments on earth… and in space.
From the hottest desserts to the coldest, driest regions of Antarctica, tardigrades have proven themselves to be nearly indestructible in all environments. After noticing that UV-C radiation, a powerful form of radiation blocked from earth due to our atmosphere, had little effect on tardigrade health, scientists had a great idea: these organisms may be able to survive space. And survive they did. The scientists launched a culture of tardigrades into space and left them attached to the outside of a satellite for 10 days to confirm that space wouldn’t shake the bears at all. The tardigrades survived.
Now, with space travel technology allowing longer crewed voyages into space, scientists are looking to water bears for ideas to help astronauts survive the perils of space travel. Tardigrades can engage in cryptobiosis, a state of stalled metabolism during which water bears operate using 0.01% of their usually expended energy. This is similar to an extreme version of hibernation during which the tardigrades dehydrate, forming a small, shriveled ball called a tun. In this form, they can survive the harshest conditions imaginable, including a pure vacuum, temperatures over 300 °F and under -400 °F, X-ray and ultraviolet radiation, extreme pressures equivalent to 6,000 atmospheres, and more. Researchers around the world have one not-so-simple question… how?
There are several ongoing theories regarding tardigrade survival. One concerns trehalose, a synthesized sugar that can occupy up to 25% of the tardigrade’s biomass. Researchers think this sugar is used to displace water surrounding proteins and membranes during the tardigrades cryptobiotic state. This is an important adaptation as water forms crystals when freezing, piercing membranes and leading to cellular damage. Other researchers think the secret to their survival lies elsewhere, such as with intrinsically disordered proteins. While most proteins have a highly regulated folding pattern and shape that correlates with function, intrinsically disordered proteins are more random, taking on different shapes according to surrounding environments. Researchers at UNC credit the high number of these randomized proteins with tardigrade desiccation survival, since these proteins, like trehalose, expel water and prevent damaging crystallization. Other research has proposed a more coordinated metabolic effort in which genes controlling replication and metabolism are downregulated during cryptobiosis while those serving a more protective purpose are upregulated, followed by an increase of DNA repair proteins following revival.
Regardless of the method, these tiny animals’ ability to survive the most extreme environmental conditions our universe has to offer will surely be of interest to researchers for decades to come.
(images credit: Eye Of Science/SPL/Solent, waterbears)
Careful! It’s got claws! –
(images credit: Willow Gabriel, Goldstein Lab)
These small, segmented animals were discovered by Johann August Ephraim Goeze, an aquatic zoologist, in 1773. Over 900 species of water bears have been found everywhere around the world – from the Himalayan mountains (at elevations of over 6000 meters) to deep ocean areas (4000 meters below sea level). They are most often discovered on mosses, lichens, and various types of sediments. An easy way to observe them is to soak a piece of moss in spring water.
Tardigrade in the moss water:
(image credit: Jasper Nance)
Freeze them, boil them, dry them, expose them to open space & radiation – and after 200 years they’ll still be alive!
The amazing thing about these tiny, 1mm creatures is just how resilient they are to about everything. You can put them in space, in hot sea vents, and freeze them – no matter what you do, they’ll survive.
You see, Tardigrades can survive in:
Extreme cold (at -272 degrees Celsius for a couple of minutes, or at -200 degrees Celsius for days on end)
Extreme heat (being heated to 181 degrees Celsius for a couple of minutes)
Extreme radiation (easily surviving 5,700 grays of radiation. A gray is about as much radiation as 5,000 chest x-rays. 10-20 grays can easily kill a human and most animals.)
Extreme dehydration (A tardigrade can survive for a decade with no water)
In a vacuum – Yes, a water bear can survive in space!
These tiny organisms can be found everywhere – in fact, there are probably hundreds of these creatures just a few meters from where you are standing. They aren’t as publicized as they should be, but these creatures are truly fascinating. It’s amazing that these miniscule beings can survive for so long in the circumstances when others will certainly die out.
So here’s to Tardigrades, nature’s greatest survivors!
They are also kinda cute…(on the left is the early Eutardigrade illustration by Andrew Pritchard):
…and they look great in art: