Extremophiles refer to animals that are adapted to living in the most extreme environments. From beetles that use anti-freeze proteins to stop their blood from freezing to fish living at 8000 meters below sea level, life has found a way to change to survive in nearly every environment. However, the toughest creatures on earth are microscopic creatures called tardigrades.
What’s a Tardigrade?
Tardigrades are invertebrates, usually inhabiting moss or lichens or pools of water leading to their nicknames of ‘water bear’ and ‘moss pig’. They’ve been found seemingly everywhere, from the Himalayas to the deep sea and from the tropics to the poles. What-ever the conditions, tardigrades have managed to adapt to fill hundreds of micro-niches.
Reportedly, species of tardigrade can survive temperatures ranging from 1K (close to absolute zero) to 420K, 5,000 or 6,000 grays of ionising radiation and pressures 6 times that of the bottom of the Mariana trench. Tardigrades can go almost 30 years without food or water, drying out to 3% water mass only to re-hydrate and go on to forage and reproduce perfectly fine. This is a process called cryptobiosis where the animals suspend their own metabolism in order to survive extreme lack of water or oxygen.
In 2007 tardigrades sent into space survived for 12 days on the outside of the capsule, exposed to the unforgiving vacuum of space. To put that in perspective, if a human being were to walk around in space without a space-suit they would die in less than a minute, lack of oxygen causing them to pass out in around 15 seconds.
Fossil records have shown tardigrades have existed on earth for 530 hundred million years, since the Cambrian period. These creatures have managed to survive several extinction events since then, including the one that wiped out the dinosaurs and are still thriving today.
Why are Tardigrades important?
The tardigrades ability to go into cryptobiosis presents incredible possibility. In most animals the complete loss of metabolism leads to death, however the tardigrades ability to stay in this state for decades and still revive themselves is now being used by scientists on larger organisms.
Japanese scientists used a tardigrade sugar called trehelose to preserve a rat heart. They kept the heart in a fridge (4 degrees centigrade) for 10 days and then managed to revive it. This process could be used to keep organs for human transplants viable for longer which could save thousands of lives a year.
Furthermore, the ability to live in suspended animation may mean advances in space travel with an ability to travel across many light years.
Tardigrades: The end?
Tardigrades were here before us and they will most likely outlive us. An asteroid big enough to wipe out tardigrades would need to have a diameter of over 300 miles and enough energy behind it to evaporate the oceans. In comparison, the asteroid that killed the dinosaurs was a mere 17 miles in diameter. The likelihood of this occurring however is so small it is likely the sun will die first. In conclusion, the tardigrades are here to stay, probably permanently.