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We’ve all heard about tardigrades at least once in our lives and recently, maybe a little too much. We have also seen the cute frumpy pictures on the internet, but what are they? They are micro-organisms that have been hypothesized to not only survive space-like conditions but maybe actually be from outer space!

What are Tardigrades?

Tardigrades are small microscopic organisms that are usually half a millimeter in size with eight clawed legs. They have been in the news for their many indestructible qualities such as being able to survive space and recently, proof that they can even survive UV radiation. Surprisingly, contrary to popular belief that they are just one species, the term ‘tardigrades’ refers to an entire PHYLUM! There are over 1000 species of tardigrades, each with its own unique qualities. There have been many questions as to where they originate from and what their ancestry looks like, so we will be discussing that in this article.

How common are they in our environment?

They’re a little too common to be honest, which is surprising since most of us are completely unaware of this micro-organism. Their habitat mostly lies in wet environments such as mossy, lakes, or even at the bottom of the ocean, giving them the name ‘moss piglets’ They have the ability to practically survive any environment so it won’t be surprising to find them anywhere else! They have been known to survive temperatures ranging from -200o C right up to 300o C. That range on its own is impeccable, making them one of the toughest creatures out there. Finding them at the bottom of the ocean was also not very astonishing because they have been known to survive conditions in space where the pressure levels are 200 times that of what is found on Earth!

Tardigrade Water Bear
Tardigrades (Source: https://scitechdaily.com/researchers-discover-how-water-bears-survive-extreme-conditions/)

What is their ancestry like?

Because of the way they look, it has been hypothesized that tardigrades have evolved from arthropods (insect phyla) but molecular and genetic analysis has indicated that they could be a mixture of Arthropoda and even organisms from Onychophora (a group of worms also known as pan-arthropods for their similarities with arthropods). So, no. They do not come from outer space and are from our very own beloved planet. But they have managed to survive for over 500 million years without any threat to their survival and it is assumed that they will survive long after we’re gone. From modeling analysis that has been done, it has been discovered that these creatures could have survived over 5 extinction-level events! (Yes, the dinosaurs as well)

Mechanism of survival: Cryptobiosis

These creatures have been found to be able to survive daunting conditions due to their ability to go into a state known as cryptobiosis. This means that they can go into a dormant state where they literally lose 99% of their water, pull their legs in, and form a thick covering around themselves. When they’re in this state, they’re known as TUNS and their metabolism is as low as 0.01% of their normal metabolism. This is due to the presence of trehalose (a type of non-reducing sugar) that is present in their outer layer and keeps them protected! This fascinating ability of theirs makes them resistant to almost any life-threatening situation. We wish we could do that! They also show many other modes of survival such as osmobiosis (extreme salinity), chemobiosis (toxic chemicals), anoxybiosis (absence of oxygen), etc. They have also been known to survive due to the presence of damage protection proteins known as DSup.

The Internal System That Lets a Tiny Tardigrade Micro-Animal Survive Severe  Dehydration for Years at a Time
The difference between both survival states (Source: https://laughingsquid.com/tardigrade-can-survive-dehydration-for-years/)

Mind-blowing facts!

  • They can survive extremely hot and cold temperatures
  • Have the ability to absorb UV radiation and shine bright blue!
  • Can repair their own DNA when irradiated
  • The longest surviving tardigrade was found to be 120 years old due to cryptobiosis (although this was never replicated)
  • They have already been planted on the moon as part of a lunar library where human DNA and tardigrades were sent as part of a backup mission in case anything untoward happened on Earth
  • They can stretch out their metabolic rate in the absence of optimal levels of oxygen

Implications of Tardigrades in science

Tardigrades have a huge impact on science because understanding their mechanisms of survival could open up a whole new avenue of possibilities for us. For example, understanding how they survive radiation and repair their own DNA can help us formulate new cancer treatments. They have been used to create DRY VACCINES where the water content of the vaccine is replaced with trehalose which increases their storage longevity and removes the requirement of storing them in refrigerators. They could also be used to prove the panspermia process which I have already discussed previously.

All in all, these tiny curlings are not only cute to look at with the numerous pictures that we have of them but are also the toughest creatures out there. They’ve survived the longest amongst most species and will continue to do so.

References

Devasurmutt, Y., & Arpitha, B. (2016). An Introduction to phylum Tardigrada-Review. International Journal of Latest Technology in Engineering Management, 5, 48-52.

Fox-Skelly, J. (2015, March 15). Tardigrades return from the dead. Retrieved from http://www.bbc.com/earth/story/20150313-the-toughest-animals-on-earth

Marples, M. (2020, October 19). When this creature faces deadly radiation, glowing is the only option. Retrieved from https://edition.cnn.com/2020/10/19/world/glowing-fluorescent-tardigrades-discovery-scn/index.html

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