Tardigrades- The Near Immortals
“To our surprise, we found that although nearby supernovas or large asteroid impacts would be catastrophic for people, tardigrades could be unaffected,” David Sloan, a researcher at Oxford.
We all love sci-fi films right!? Harbinger Dawn is one of my favourites. In the movie, the characters dealt with deadly mutated creatures named Tardigrades. For all those who have absolutely no clue about where this is going, and who have no idea about who these creatures with a very weird name are, you are about to learn about one of the most fascinating animals on this planet, who not only look like a bunch of cute alien-like creatures but they can also be the key to human evolution.
What’s a Tardigrade?
Tardigrades (Tardigrada) also known as water bears or moss piglets are a phylum of eight-legged segmented micro-animals. They are close relatives of arthropods and are mostly about 1 mm or less in size (according to the World Tardigrada Database).
A tardigrade’s body typically consists of only 1,000 cells. They have a well-developed head region, barrel-shaped bodies and four pairs of stubby legs. The legs are without joints while their feet have 4–8 claws each. Tardigrades have no known specialized organs of circulation or respiration.
Now, they may look like cute, adorable miniature bears, but these eight-legged microscopic animals have been to outer space and some say that they are immortals and might even survive the apocalypse. So, let’s delve deeper into the world of Tardigrades and try to question their “immortality”.
Where did they even come from?
Tardigrades have been on earth for about 600 million years, preceding the dinosaurs by about 400 million years. They were discovered in 1773 by the German zoologist Johann August Ephraim Goeze, who dubbed them Kleiner Wasserbär (little water bear). In 1777, Italian biologist Lazzaro Spallanzani named them Tardigrada which means “slow steppers”. According to the Integrated Taxonomic Information System (ITIS), there are currently about 1300 known tardigrade species.
Where do they live?
Tardigrades live in a variety of habitats worldwide ranging from damp mosses to the sands to fresh waters. The wide range of external conditions is the reason why a large number of species have evolved.
What do these mystical creatures even eat? Immortality crystals? Infinity Stones?
Well obviously, no; most tardigrades suck fluids from cells in plants, algae and fungus, puncturing cell walls with needle like stylets in their mouths and hoovering up the liquid inside.
However, some species can consume entire living organisms, such as rotifers, nematodes and even other tardigrades. Do not worry, you won’t find yourself getting eaten by a tardigrade someday!
Now that we have gist of these tiny bears, let’s have a look at their remarkable abilities and try to understand what’s so special about them.
Tardigrades- The Superheroes
The most fascinating feature of the tardigrades is their ability to withstand extremely low temperatures and desiccation (extreme drying). Many scientists have reported tardigrades in hot springs, on top of the Himalaya, from the polar regions to the equator, under layers of solid ice, and in ocean sediments. They survived all 5 mass extinction events on the earth and they are even known to survive after exposure to outer space.
Sounds like something completely out of this world, but there is an explanation to this. In unfavourable conditions, these organisms go into a state of suspended animation (called the ‘tun’ state) in which their body dries out and they look like a lifeless ball. Their metabolism declines to as little as 0.01% of its normal rate. With more than 95% of water expelled from their bodies, they enter a near death state called cryptobiosis. How do they survive? Well, during cryptobiosis, its cells are protected by water-soluble proteins also known as Tardigrade Disordered Proteins (TDPs). These TDP molecules form a tough, glasslike cocoon around cells and protects it from any external damage keeping all the cellular material safe. Their DNA is protected from radiation by a protein called ‘Damage Suppressor’ (dsup). When conditions are more hospitable, they can be revived and brought back to life even after decades. In 2015, the BBC reported that a researcher in Italy purportedly revived a tun from a dried-out piece of moss that was over 120 years old.
All of this might have raised tons of questions, and you might as well think Tardigrades are actually immortals. I hate to burst your bubble, but tardigrades aren’t any sort of aliens and are not immortal. Not counting their time in dormant states, the lifespan of tardigrades ranges from three to four months for some species, up to two years for others. Tardigrades can survive in extreme conditions but this does not mean that they are indestructible. Even in their ‘tun’ state, one hour of exposure to water at 82.7 °C (180.9 °F) can kill a tardigrade. Scientists found that these creatures couldn’t survive speeds above 2,000 mph when shot out of a gun. This also suggests that the water bears that crashed on the moon in 2019 didn’t survive as well.
As disappointing as all of this may sound, Tardigrades not being immortal does not mean that they are not of any use to humans. In fact, there’s a plethora of stuff we can learn from a tardigrade’s genome and we can utilize its genes in ways that can someday make us ‘superhumans’.
Tardigrade’s Genome and its Uses
Tardigrade genomes vary in size, from about 75 to 800 megabase pairs of DNA.
- The genome of Ramazzottius varieornatus, one of the most stress-tolerant species of tardigrades, was sequenced by a team of researchers from the University of Tokyo in 2015. While previous research claimed that one-sixth of its genome was acquired from other organisms, it is now known that less than 1.2% of its genes were the result of horizontal gene transfer.
- This study had also found a high expression of TDPs and Damage Suppressors. Now, as we know that damage suppressors protect a tardigrade’s DNA from radiation (especially X-ray radiation), we can apply this Dsup protein to human cultured cells.
- In August 2020, a team experimented with these proteins and applied them to human cells. They found out that Dsup proteins were able to suppress X-ray damage to human cells by around 40 percent!
- They also suggested that strong electrostatic attractions along with high protein flexibility helps the Dsup to form a molecular aggregate, which shields the human DNA and helps suppress X-ray damage.
- By genetically modifying humans with a tardigrade’s DNA which would shield our cells from radiation, we would be able to withstand the deadly effects of spaceflight
Time for a Medical Revolution
A new species of tardigrades was found to endure UV radiation. This can create a revolution in Medical Science as well. They can be used to get rid of hard-to-kill bacteria and virus. This discovery was actually made by chance. Researchers at the Indian Institute of Science (IISC) exposed the water bears to extreme conditions. They happened to have a germicidal UV lamp in the lab, so they hit their specimens with it. The dose of 1 kilojoule per square meter, which killed bacteria and roundworms after just 5 minutes, was lethal to tardigrades as well; most died after 24 hours. But when they hit a strange, reddish-brown species with the same dose, all miraculously survived. In fact, when the researchers upped the dose four times, about 60% of the reddish-brown bears lived for more than 30 days.
Conclusion
I’m glad that you made through this article. Now, there might be one final question in your head, “How would all of this information serve the human race?”
To sum up, the peculiar characteristics and unique abilities of tardigrades can be further explored and researched upon and one day these cute resilient bears might as well create a path for us humans to achieve what tardigrades couldn’t, i.e., ‘Immortality’
