Are Tardigrades Immortal?

Water Bears and the Secret of Immortality – Tardigrades

Water bears, also known as tardigrades, are the most immortal creatures on Earth (and sometimes even in space), able to withstand extreme conditions. We've been hearing his name a lot lately. Because it attracts people's attention again and again, both with the studies done on it and with its mysterious worlds. And the most important reason is that these creatures can come to life after drying out!

Water bears (tardigrads) live both on land and in water.

But they say that those living on land are more resilient. Because these creatures need water to live. Water bears living in wetlands such as seas and lakes do not face the danger of dehydration, so their self-protection mechanisms are worse in such areas.

What kind of creatures are these water bears?

These water bears are microscopic creatures. It has a head, a body and 4 pairs of legs. Of course they look better with an electron microscope. The photo in the cover image was already taken with an electron microscope. They generally ate a plant-based diet. They choose lichens, algae and mosses as food. But there are also some that eat both carnivores and herbivores. There were even some who ate their own species. They breathe through diffusion through their body surfaces.

They have cutting protrusions on the sides of their mouths and on their feet. Its body has a flexible structure, but as it grows, it needs to replace its shell with a new one.

As far as we know, there are over 1100 species. Most of them live on land. And their history is quite old. They found fossils that are 500 million years old.

Where do their names come from?

The reason why they are called water bears is that there is a thin layer of water surrounding their bodies. Most water bear species live on land, but there are aquatic species as well. But these were not as durable as the ones on land. We mentioned the other names as Tardigrades. This comes from the word "il tardigrado" meaning "the one who walks slowly". This name was given to them by the German zoologist Johann August Ephraim Goeze, who discovered these creatures in 1773.

The Secret of Their Immortality and the Tun State

Water bears can show great resilience to extreme conditions. These creatures were kept at 125 degrees for 3 minutes and survived. After being exposed to a temperature of 151 degrees, they came to life as soon as they touched the water. They survived after high amounts of radiation and could withstand high doses of radiation in their normal form. So what is the secret of this?


Water bears have a way of enduring extreme conditions that they call the "tun state." While reaching this state, they throw out 95% of the water in their bodies and pull their legs inwards. They become in a death-like state and their metabolism slows down a lot. In this way, they minimize water loss and can survive for years in this state. After 30 years in Japan, tardigrades that were taken out of -20 degree ice came back to life when they were placed in water. 2 out of 3 water bears survived. They observed that 1 in 3 people who did not survive died after being revived. The reason they died was that standing in a state of trance for so long damaged their bodies. Of course, everything has a limit.

Water bears in full form can withstand X-rays with an intensity of 570 thousand Rad, and 500 Rad is enough to kill a human. Again, they were able to withstand 600 megapascals (MPa) pressure while in tun form. For comparison, the pressure in the Mariana Trench in the Pacific Ocean, the deepest place in the world, is around 100 MPa. (You can click here for more detailed information on this subject)


The most extreme condition I have heard is that they even sent these animals into space. And when some of them came back, they were able to come out of the state and live. In 2007, they placed thousands of them on the outer surface of a satellite and sent them. Some were placed to be exposed to radiation, but most of them survived and survived. In addition, those sent to this space were able to withstand the vacuum effect. Most of the eggs of the arriving females hatched into healthy babies.

As you can see, tardigrades can even withstand extreme conditions created by humans in laboratory environments that do not exist on Earth. But despite this, they did not live in such extreme conditions. You can encounter them using a microscope in places near water and in wetlands.

5 Fascinating Features of Tardigrades

1. Incredible Survivability: Tardigrades are renowned for their extraordinary ability to survive in extreme conditions. They can endure temperatures ranging from just above absolute zero to over 150°C, withstand immense pressures, radiation levels, and even the vacuum of space.
2. Cryptobiosis: One of their key survival mechanisms is a state called cryptobiosis. When conditions are harsh, tardigrades can dry out completely, reducing their water content to 1% or less. This state, known as a 'tun', allows them to survive for years, even decades, without water.
3. Tiny Size: Tardigrades are micro-animals, typically measuring between 0.3 to 0.5 mm when fully grown. Despite their small size, they're visible to the naked eye as tiny, slow-moving specks.
4. Diverse Habitats: They are found in diverse environments ranging from the deep sea to the high Himalayas, from polar regions to equatorial jungles. Tardigrades can live in moss, lichens, leaf litter, soil, and marine or freshwater sediments.
5. Longevity and Reproduction: Tardigrades have a lifespan of about 2-2.5 years. They reproduce through a variety of methods, depending on the species, including sexual and asexual reproduction. Their ability to withstand harsh environmental conditions also extends to their eggs, which can remain viable after being exposed to extreme environments.