A Tardigrade: The Most Durable Animal on the Planet
A tardigrade, also sometimes known as the water bear, is one the most durable creatures ever discovered, although they look like a chubby, 8-legged gummy bear. Their legs each have 4-8 claws that resemble the claws of a bear. This is why they have earned the name ‘Water Bear’ but they are also known by the name ‘Moss Piglet’ because they are also found in moss.
Although they are only around 0.5 millimeters long, they can survive extreme conditions. For example, it can survive at 151 degrees Celsius, which is way above the boiling point of water. They can survive in the vacuum of space, and can also tolerate temperatures as cold as 272 degrees Celsius, which is only marginally above absolute zero! These micro animals can survive a pressure of over 6000 atmospheres, which is nearly 6 times the pressure of water in the deepest ocean trench, Mariana’s trench, and can go decades without food or water!
In case you are not satisfied yet, even if you expose them to extreme radiations and they will come out victorious. Scientists have found out that the lethal dose of gamma rays to kill tardigrades is 5,000 Gy while the lethal dose of heavy ions is 6,200 Gy. For humans, 5-10 Gy is lethal.
These extraordinary capabilities of tardigrades come from their ability to halt all their metabolic activities completely. This is known as cryptobiosis and when a tardigrade gets into a cryptobiotic state, it is known as ‘tun.’ When a tardigrade enters cryptobiosis, it loses more than 95% of the water stored in itself, essentially, dehydrating itself. In this state, the water bear creates different proteins and sugars that help protect its cells. Once these cell protectants are synthesized, the water bear reduces, and at times suspends, its metabolism.
Scientists have immersed them in liquid helium, pure alcohol, hydrogen sulfide, and even exposed them to deadly radiation. However, when removed from these hostile environments, they simply emerge from their cryptobiotic state, rehydrate themselves, and amble away on their four pairs of stubby claw-tipped legs, completely unharmed.
Scientists are now trying to find out whether tardigrades use the tun state to survive other stresses. If we can understand how they stabilize their sensitive biological molecules, perhaps, we could use this knowledge to develop many new technologies, such as stress-tolerant crops that can cope with the Earth’s changing climate. By studying how tardigrades can survive the vacuum of space, we can learn more about the limits of life, and how to safeguard astronauts. Tardigrades can even answer a critical question: can life exist on a planet far less hospitable than our own? These are just some ideas if we do further research into this incredible species.