What is the toughest animal on earth?
But the award for the most resilient animal has to go to the moss piglet – a microscopic critter who can survive even in the vacuum of space.
Moss piglets, or tardigrades, are not new to the scientific community. However, their tenacity has fascinated biologists for centuries. A recent study in September published in Nature Communications have shown that we may even be able to use their DNA to help our cells withstand harmful radiation. Understanding what makes these little guys so tough may one day help our survival in space as well.
A moss piglet (Credit: Eye of Science/SPL)
So what exactly is a tardigrade?
Tardigrades are tiny creatures not much larger than a millimeter in length. Also known as ‘water bears’, these animals lumber lazily around in their aqueous natural habitat like bears out of hibernation. At first glance, their plump round bodies, four pairs of stumpy legs, and slow gait make them unlikely contestants in a race of hardiness. However, their ability to thrive in the harshest of environments is astonishing.
Movement of tardigrades (Credit: Craig Smith from YouTube)
Tardigrades commonly live on moist mosses and lichens feeding on plant cells and bacteria. But scientists have collected them from the deepest seas of Mexico to the highest mountains of the Himalayas.
The tardigrade’s unique ability to survive in extreme environments has prompted scientists to test them to their limits.
In 1998, Japanese researchers put tardigrades to the test by crushing them under 600 megapascals (MPa) of pressure. This pressure is six times greater than the water pressure in the deepest part of the ocean in the Mariana Trench, and the tiny water bears were still able to subsist. To put things in perspective, the strongest human free divers have only been known to survive 3 MPa of pressure.
In 2007, tardigrades became unwilling astronauts as they were shot into space. Far from their native environment, the water bears were left naked in outer space without oxygen, exposing them to hard vacuum and deadly solar radiation. After 10 days, a few tardigrades still managed to survive.
What is their secret to survival?
When taken out of water and dried out, tardigrades enter a state of suspended animation and curl up into a tight ball called a “tun”. In this state, the tardigrade reduces its metabolism by 99.99 percent and produces a mixture of molecules that prevent it from freezing and also encases it in a matrix of biological glass.
A tardigrade in its tun state (Credit: Eye of Science/SPL)
This combination of survival mechanisms is the key to the tardigrade’s resilience. In this dormant state, they have been show to survive for up to 10 years without water. Not even temperatures near absolute zero can crack their shell.
So the next time you are asked to name the toughest animal on Earth, forget the elephant and remember the tardigrade!
Justin Tao
