Tardigrades (Tardigrada) are probably the most paradoxical animals of the planet. On the one hand, these microscopic organisms are incredibly cute (right?), Looking like tiny airships that move harmlessly on their stubby little legs. Precisely because of their appearance and way of moving they are often called ‘water bears’, but we prefer to call them appropriately: tardigrades. Aside from their funny looks, they present themselves to the world as the toughest and most indestructible creatures on Earth. For example, it is the only living being that would survive an astronomical cataclysm.
At just 1 millimeter long (or even less), their tiny bodies contain biological superpowers that help them endure conditions that could spell certain death for other organisms. Surely you are already wondering. Considering their stamina, how long can these creatures live?
It depends on where they are. Tardigrades live almost everywhere on the planet , but they are best found in humid habitats, such as moss that adorns river stones, lichens, or ferns. When tardigrades have enough food and water to maintain their bodily functions, they live for about 2.5 years, according to Animal Diversity Web , a database managed by the University of Michigan.
And yet tardigrades can survive much longer if they enter a state called cryptobiosis , which kicks in when environmental conditions become unbearable. It is an extraordinary ability to cope with extreme environments.
Cryptobiosis puts tardigrades into a state where their metabolism slows down, reducing their need for oxygen and releasing their cells of water almost completely. In this limited state, tardigrades mimic death so closely that they can survive in places without water, at temperatures as low as -200 ° C and as high as 151 ° C. When these tardigrades are exposed to water again, they simply revive and return to normal life within hours. That easy.
In 2016, an article published in the journal Cryobiology showed that a handful of tardigrades, frozen had survived in this frozen state for 30 years until they reestablished in 2014. The tardigrade’s talent for self-preservation is believed to be reduced, in part, to its production of unique proteins that can lock fragile cellular components in place. According to a 2017 study in the journal Molecular Cell , membranes, proteins, and DNA are destroyed, punctured, and broken when cells dry out.
A special biochemistry
In addition to being frozen, boiled and dried, tardigrades are known to withstand pressures of up to 600 megapascals, six times what they would experience at the bottom of the sea. Only half of this pressure would kill most organisms on Earth.
Many researchers have done their best to test the resilience of tardies, expelling them (in their limited state) into space. In many of these studies, tardigrades traveling through space were exposed to direct solar radiation and gamma rays; far from something happening to them, when they were placed in a water-filled petri dish on Earth, they basically walked away and said ‘okay, where’s dinner?’, and that is that tardigrades seem to be able to resist radiation and even repair their DNA, which may explain why they are so resistant to the extreme effects of radiation.
Although it is clear that they cannot live forever, the fact that tardigrades can survive in a reduced state for 100 years or more is an exaggeration, for example. Only a few tardigrades survive the torments of experimental freezing, boiling, and radiation that humans put them through.
But there is another way to assess their resistance: at the species level . Not only have tardigrades existed since the Cambrian period 541 million years ago, but they may also continue to outlive us, and likely all other life on Earth, according to a 2017 article in Scientific Reports that found that if an event Cataclysmic as an asteroid impact fell on Earth and destroyed life, a group of tardigrades inhabiting the ocean’s Mariana Trench would endure.
Tardigrades seem to represent our surest hope for sustaining life on this planet …
