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Tardigrades- Animals Full of Surprises

By Maya Komar-Fletcher

Tardigrades, also known as water bears, are an elite category of animals known as extremophiles. They are aquatic animals, with intriguing properties that make them practically indestructible. Thought to have the ability to survive global mass extinctions, they can endure considerable, rapid changes in pressure, freezing temperatures, starvation, oxygen deprivation as well as extreme radiation. [1]

To be active and reproduce, the Tardigrade needs to be exposed to a wet environment such as places covered in lichens or mosses. [2] They can be found in the most unexpected parts of the world- from thousands of meters under water to mountain peaks. They can inhabit many different ecosystems with their incredible ability to withstand a multitude of climates. Perhaps one of the most intriguing factors of their body is that if they are deprived of this moist environment or find themselves in extreme conditions,they retreat into a so called ‘tun state’ or a state of cryptobiosis. They expel up to 90% of water and contract their head and limbs. Their metabolism is suspended due to the absence of water and can remain in this state for decades. When environmental conditions improve, the water bear activates its metabolism once again, aided by hydration from water intake.[3] When activated, the Tardigrade wakes up in the same state it was in when entering the cryptobiosis- it does not biologically age when in the tun state. Effectively, this process has been called the “Sleeping beauty hypothesis” [4] or “death and resurrection”. [5]

Another fascinating property of tardigrades is their ability to produce a distinctive protein known as Dsup (“damage suppressor”), which protects their DNA from any form of radiation. Questions began to arise about the use of this protein within humans. After all, humans would greatly benefit from protection from solar radiation, x-rays or radiation therapies. According to a 2016 Article published in Nature, a team of Japanese scientists lead to the multiplication of this protein in human cells - bred in vitro. This protein increased their immunity to radiation by 40%.  

So, theoretically, we are able to apply the protection that tardigrades have to our own cells… 

James Kadonaga, an American biologist, along with a group of researchers, has recently discovered how Dsup causes this immunity. Their research mentioned that “Dsup binds to a structure called chromatin, a package that holds a cell's long strands of DNA in a dense package. When cells are bathed in X-rays, water molecules split and form highly reactive particles  of oxygen and hydrogen called hydroxyl radicals; these radicals can damage DNA inside cells.” The scientists then proceeded to find that Dsup can protect DNA from these hydroxyl radicals- “ High-energy Dsup has a cloud-like structure; the cloud surrounds the DNA's chromatin envelope, blocking hydroxyl radicals and preventing them from disrupting cellular DNA.” [6]

These unique properties of the tardigrade have grasped the attention of the space exploration field with questions arising about the possibility of tardigrades surviving in space. During the FOTON-M3 mission in September 2007, an experiment was conducted in an experimental platform provided by the European Space Agency. Tardigrades were exposed to a space vacuum and various sources of UV- radiation spectral ranges. All species of the tardigrade tested survived the exposure to a space vacuum well and were unaffected, whilst the exposure to both the vacuum and galactic radiation simultaneously, resulted in the survival of certain individuals. So far in the development of science, only lichens and bacteria have been reported to endure the combination of these two conditions. [7] The tardigrade is the first animal to survive this ultimate extreme and could potentially be left on the surface of a different planet and thrive.
 

Could you imagine astronauts falling into a cryptobiosis state for 5 years, until they safely reach their newly discovered planet, and then waking up as if no time has passed? Could you imagine humans completely immune to radiation, free of many types of cancer, able to be exposed to the sun or even space without any risk? These are only some of the questions researchers are asking, theorising on a special set of properties which could be introduced to the human race. A lot remains to be discovered about the exact mechanics behind the qualities of tardigrades, yet we never know what the future could allow us to implement into our bodies…  

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