When it comes to the phrase “top 10 reasons,” tardigrades (aka water bears or moss piglets) absolutely earn the spotlight. These minuscule critters pack more personality and scientific intrigue into a body that barely reaches a millimeter. Their adorable nicknames are just the tip of the iceberg—behind those squishy, eight‑legged silhouettes lies a world of astonishing abilities.
Why These Top 10 Reasons Matter
10 What the Heck Are They?
There are more than 1,100 known species of these pint‑sized invertebrates, and scientists are still debating exactly where they fit on the tree of life. Although they share several traits with arthropods—think crustaceans, spiders, and insects—their unique anatomy keeps them in a classification limbo. Some early researchers even mistook them for bacteria because of contaminated samples, but later genetic work proved they belong to the eukaryotic domain.
In plain language, tardigrades are multicellular organisms whose DNA lives inside a defined nucleus, setting them apart from single‑celled bacteria. Modern microscopes and molecular tools have finally let us peer into their microscopic world, confirming that they’re far more complex than the early misconceptions suggested.
9 Little Body, Killer Teeth
Photo credit: Wikimedia Commons
Tardigrades belong to a special group called extremophiles, meaning they can thrive where most life would quit. Their bodies are translucent and encased in a four‑segment exoskeleton, topped with eight stubby legs—each ending in four microscopic claws for gripping surfaces. They typically measure between 0.5 and 1.2 mm, rarely exceeding a millimeter, and sport a distinct fifth segment that houses their head, even though it looks a bit squashed.
Their mouths are round and can extend outward like a tiny spear, armed with razor‑sharp stylets that pierce cells and draw out nourishing fluids. While this sounds vampiric, they’re not after blood the way mosquitoes are; they simply sip the liquid inside their prey, and fortunately, humans aren’t on the menu—at least not yet.
8 Been Around for Millenia
Photo credit: Wikimedia Commons
Although they’ve only recently become a hot research topic, tardigrades were first spotted in 1773 by German pastor J.A.E. Goeze. Three years later, Italian biologist Lazzaro Spallanzani christened them “Tardigrada,” meaning “slow stepper.” Fossil evidence now shows they’ve been roaming Earth for at least half a billion years, making them one of the planet’s oldest terrestrial residents.
That staggering timespan dwarfs humanity’s brief existence, reminding us that life can persist through cataclysms that would wipe out most other organisms. So next time you glance at a mossy rock, remember you’re looking at a living relic that has survived more epochs than any dinosaur.
7 Desiccated and Frozen…but Alive
These little guys are most often found in water, especially fresh water. But they also live in every habitat on Earth where water is present, from Antarctica to the oceans to tropical rainforests to mountaintops and even in sand and soil. The easiest place to find and study them is in the water film found on mosses and lichens. So yes, you can likely find them in your own backyard, especially if you live near a body of freshwater!
They are considered aquatic since they need water to live. The water around their bodies is necessary to allow gas exchange and prevent them from desiccation, basically being a sun‑dried tomato or dehydrated fruit. But, if they are removed from the water, they don’t actually die. They can be reanimated once they are returned to that life‑giving H2O. And that isn’t all! They can be frozen at extremely low temperatures for very long periods of time and still be reanimated once they thaw. How awesome is that? They’re getting cooler with every new thing we learn about them.
6 A Fungi Diet
So what do they eat? Mainly they feast on mosses, flowering plants, bacterias, and lichens, or as they are more commonly known, fungi. They are also known to slurp on animal cells, and some of them are actually cannibals, eating other tardigrades. They suction out the fluids that are nutrient‑rich after using that kind of disturbing mouth to puncture the cell walls and membranes of their targets. It’s a really good thing they don’t have a taste for us, or they wouldn’t be quite so cute anymore.
5 Extreme Survival
Let’s learn a little more about that remarkable ability to come back to life that has made the scientific world so keen to study them further. Through a process known as cryptobiosis, they are able to slow their metabolic rate to as low as 0.01 percent, essentially making it possible for them to survive without eating. Their organs are protected by a sugary gel that continues to produce a large amount of antioxidants.
On the occasions that they are exposed to extremely low temperatures or dehydrated, they form something called a tun. They curl into a tiny ball by tucking in their head and hind legs. And in freezing conditions, they can also somehow prevent the growth of ice crystals. There’s no way science is finished studying that ability.
And if the water they live in has lower than normal oxygen levels, the tardigrades can stretch out, slow their metabolic rates, and absorb oxygen through their muscles. As if all of this isn’t incredible enough, they can produce a protein that protects their DNA from radiation damage. They can also survive some noxious chemicals, low‑pressure vacuums, boiling alcohol, high pressure such as deep ocean depths, and changes in water salinity. It’s becoming less of a wonder how they have survived so many mass extinctions over time!
4 Brace for Impact
Water bears aren’t entirely indestructible or immortal despite their many shocking survival capabilities. It may seem that way, but they do have some weaknesses and will eventually die. One thing they definitely cannot survive is human stomach acid, which is a good thing because you’ve almost certainly drunk some in your lifetime without knowing. And their natural life span, without being frozen or desiccated, is about two and a half years. And they can’t survive an impact in excess of 3,218 kph (2,000 mph). Yeah, people shot them out of guns to test the limits of their survival skills. Humans are so weird.
Recently it has been discovered that their life spans are greatly shortened in water temperatures of 38 °C (100 °F) or more. Climate change may be just as much of a detriment to them as it is to all other forms of life. We truly need to get better control of our habits that are speeding up that process for all of our sakes. Let’s save the bacteria‑destroying water angel moss piglet! New campaign?
3 Walk This Way
Watch them walk! The videos are out there now, and it is precious. When they are not swimming, tardigrades lumber along on those eight little legs in search of moss and mushrooms to suck dry. And they have the gait of insects 500,000 times larger than them and even crustaceans. It looks surprisingly similar to galloping. They just do it very, very slowly. Ever feel like a tardigrade without your morning coffee?
They are aquatic. Hence, water angels (hoping that catches on)! So, of course, they also swim. They do this with those miniature legs too. And they can swim a bit more quickly than they walk. They also float, but it is usually on bits of debris instead of free‑floating. So their float seems a bit more like surfing. They’d probably kill the competition at the Pipeline in Oahu, Hawaii.
2 Males Need Not Be Present
The Moss Piglets have some interesting reproduction practices too. Some species even reproduce asexually. The female lays the eggs, and they develop on their own with no need for external fertilization. Clean and efficient (but maybe not as fun). It also eliminates the need for any males in the species (um…wait a minute there). If you’re a fan of science fiction or horror films, watch No Men Beyond This Point, and you’ll see what might happen if people went the way of the self‑reproducing tardigrade!
In some species that have been observed mating, the lady lays anywhere from one to thirty eggs. But the eggs are implanted in the molting cuticle of her skin. Once the guy comes along, he wraps around her, and they work toward stimulation together, sometimes for an hour or more. The male then releases the sperm under her skin. In other species, the female sheds the cuticle completely and lays the eggs in it. The male comes along later to fertilize the eggs. The eggs take around 40 days to develop and sometimes 90 days if they have been desiccated. So it’s not the most romantic process.
1 Tiny Alien?
Because of their multitude of strange and death‑defying attributes, there’s a belief spreading that the tardigrades are aliens that arrived here on a meteor. This is probably more science fiction than fact. But that didn’t stop people from turning them into aliens. We sent them to the moon after all, if only by accident. Poor little water angels.
An Israeli spacecraft was carrying thousands of tardigrades in an effort to study their survival capabilities in the vacuum of space and the various forms of radiation. But it crashed and landed on the moon. The water bears were in a “hibernation” state and encased in artificial amber. And it is firmly believed by the program’s director that the moss piglets very likely survived and are still in their suspended animation state. Now the tardigrades are astronauts too. Truly fascinating.