Tardigrades are infamous for their ability to withstand all kinds of extreme environments, and scientists continue to unearth fascinating insights into these incredible survival skills. A new study has delved into their ability to endure freezing temperatures, and shown for the first time that they are able to stop their internal clocks to halt the aging process.
Also known as water bears, practically unkillable tardigrades carry some unique capabilities when it comes to survival. They are able to endure boiling and freezing temperatures, deal with crushing pressures at the bottom of the ocean and survive in the vacuum of space. Studies have even suggested they may live to see our Sun die.
This stems from an ability to enter a reversible state of suspended animation, putting their metabolism on hold until conditions return to normal. An interesting study last month revealed how tardigrades survive without water, with a set of proteins coming together to form protective filaments that shield cells from stress during dehydration.
This dried out state is known as anhydrobiosis, and in 2019 scientists at the University of Stuttgart showed that tardigrades can survive like this for many years through what they call the “Sleeping Beauty” effect, in reference to the fairytale about the ageless princess being woken from her slumber.
"During inactive periods, the internal clock stops and only resumes running once the organism is reactivated," explained Ralph Schill, study author from the University of Stuttgart. "So, tardigrades, which usually only live for a few months without periods of rest, can live for many years or even decades."
The scientists have remained uncertain, however, as to whether tardigrades are also able to halt the aging process when frozen, a state known as cryobiosis. So the same team took a bunch of more than 500 tardigrades and put them through repeated freezing and thawing cycles, until all the animals were dead. Meanwhile, another bunch of tardigrades was held at regular room temperature.
The intermittently frozen tardigrades lived twice as long as the control group, but when the scientists excluded the time spent frozen, the creatures had similar lifespans. The team considers this the first evidence that the “Sleeping Beauty” hypothesis also applies to cryobiosis, and proof that tardigrades don’t age when they are frozen.
"So even in ice, tardigrades stop their internal clocks like Sleeping Beauty," concludes Schill.
The research was published in the Journal of Zoology.
Source: University of Stuttgart
