Tardigrade Lifespan: How Long Do These Tiny Animals Live?

How long tardigrades live can vary considerably. Although their lifespans can be very short, they also have a special way to survive for decades.

Some types of tardigrades, which are microscopic invertebrates, live from three to four months. Other species of tardigrades can live up to two years.  

But these tiny creatures can utilize an amazing process that allows them to survive for much longer.

How Tardigrades Manage to Stay Alive for Decades

The tardigrade superpower is its ability to go into a dormant state and withstand conditions that most animals can’t.

During that time, these tiny creatures shut down their metabolism and enter a form of suspended animation. Shrinking into a “tun” state, tardigrades lose up to 97 percent of their body fluid. In that form, they look like a speck of dust.

The conditions tardigrades can survive as tuns include extremely low temperatures, drying out, solar radiation, and even the vacuum of space. They can exist in that state for several decades. When rehydrated, they continue on as active tardigrades — even reproducing!

Could a Tardigrade Live Forever?

When in its tun condition, a tardigrade is not exactly alive, but it’s not dead either. Once rehydrated, tardigrades again resemble living creatures. The longest time these animals have been in such a half-dead state and revived is currently 30 years. Previously, the record was only nine years. There’s a claim that scientists have regenerated tardigrades from dried moss found in a museum that was over a century old. So, conceivably, a tardigrade could be suspended in a tun condition for an indeterminate amount of time before coming back to life!

Once in this state, tardigrades are almost indestructible. To call them extremely hardy, in fact, would be an understatement.

They have been rehydrated back to active life after being exposed to temperatures up to 302 degrees Fahrenheit and down to minus 4. They have survived being blasted into space and kept in a freezer for 30 years. Tardigrades do not seek out or thrive in these extreme conditions, but they are able to survive them.

Where Do Tardigrades Live?

Tardigrades have turned up everywhere on Earth, from the deep sea to the desert. They live in places as diverse as hot springs and solid ice, on beaches, and in soil.

Although they exist on all continents, they are still called aquatic, as they need water surrounding their bodies to be fully alive. But since their body size is microscopic, they can exist in an active state with only a mere drop of water. They range in size from 0.3 to 0.5 mm long (that’s up to 0.020 inches). Finding a tardigrade isn’t difficult, but seeing it with the naked eye is. Any type of moss or lichen will contain untold numbers of these creatures.

How Old Is the Oldest Tardigrade Fossil?

Tardigrades are older than dinosaurs, having been on Earth for around 500 million years. Despite how long tardigrades have been on the planet, only two fossils have ever been identified. And that’s even though there are around a thousand classified species of tardigrades. Recently, however, researchers from Harvard and the New Jersey Institute of Technology discovered fossil number three. They found the fossil in a 16-million-year-old piece of amber from the Dominican Republic. The scientists used a special high-powered microscope that allowed them to analyze the entire animal in amazing detail. This led to the naming of a brand-new tardigrade genus: Paradoryphoribius.

The other two tardigrade fossils were older, dated 72 and 90 million years old, which would place them in the Mesozoic era.

Researchers have called tardigrade fossils a “ghost across time.”

What Does a Tardigrade Look Like?

Tardigrades are known as “water bears” or “moss piglets” — no doubt because of their resemblance to tiny pigs. Tardigrades have stocky bodies and four pairs of thick, short legs. At the end of their stubby legs are four to eight claws. But the thing that makes them so unusual among creatures this tiny — and of particular interest to scientists — is the way they move. They stroll on their four pairs of legs, plodding along as if they were animals 500,000 times their size.

Also, when they’re fully alive, these diminutive creatures can navigate anywhere. They move with equal ease over land and water. They cross sediments on the bottom of rivers and on the floor of the ocean as if marching in a parade. Unlike arthropods, the classification that includes insects, tardigrades don’t change their basic step patterns. Whether they’re ambling or in a hurry, they go at the same pace.

What Body Parts Do Tardigrades Have?

Tardigrades’ body parts include a brain, eyes, a digestive system, muscles, and a tubular mouth. They use their mouths to penetrate plant cells or other tiny invertebrates to absorb fluids. Although they have no bones, what they do have is a type of “skeleton” that keeps their bodies filled with a nutrient-rich liquid called “hemolymph.”

These micro-animals are unique in the world of science. They are true survivors, navigating all parts of our ever-evolving planet over many millions of years. And they still inhabit Earth today!