In 2019, Professor Ralph Schill, from the Institute of Biomaterials and Biomolecular Systems at the University of Stuttgart, proved that dried or anhydrobiotic tardigrades could survive without damage for many years minus absorbing water.

As specified in a Phys.org report, these creatures are "excellent at adapting to harsh environmental conditions."

 

It was unclear whether they age more rapidly or slower in a frozen condition or whether aging even arises to a halt. However, the mystery has now been unlocked-Frozen tardigrades do not age.

Also called water bears, tardigrades belong to the nematode family. The gait is reminiscent of a bear, although that is the only similarity.

These creatures, only roughly one millimeter in size, have managed to adapt perfectly to quickly changing environmental conditions over the period of evolution and can dry out in extreme heat, then freeze in cold conditions. Tardigrades don't die. Rather, they fall into quite a deep sleep.

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Tardigrade
(Photo: Wikimedia Commons/Dmitry Brant)
Also called water bears, tardigrades belong to the nematode family. The gait is reminiscent of a bear, although that is the only similarity.

The Sleeping Beauty

Essentially, freezing or drying out for a cell organism, explained in an earlier related report from Live Science, leads to different stress types. However, tardigrades can survive or adjust to heat and cold equally, unscathed.

They do not show any signs of life anymore. And this brings the question of what happens to the internal clock of animals and if they age in this resting state.

For dried tardigrades, which wait several years in their habitat for the next rate, Schill and his team answered the question of aging many years back. In a fairytale by the Grimm brothers, the princess falls into a quite deep sleep.

After 100 years, when a prince kisses the princess, the latter awakens, looking as young and beautiful as before. It is the same with tardigrades in a dried state; thus, this is called the "sleeping beauty hypothesis" or the Sleeping Beauty model.

Internal Clocks

The internal clocks, during inactive periods, stop and only resume running once the organism gets reactivated, explained Schill.

So, he added, tardigrades, who typically only live for a few months minus rest periods, can live and survive for many years or even decades. Until the present, it was still not clear if this applies as well to frozen animals. 

For further exploration, Schill, with his team, carried out many experiments in which they froze a total of over 500 tardigrades at -30 degrees celsius, thawed them out again, counted, fed, and froze them again.

The process was repeated until all animals died. Simultaneously, control groups were kept at constant room temperature.

Not including the time in a frozen state, the comparison with control groups exhibited a nearly identical lifetime. Therefore, even on ice, tardigrades stop their internal clocks "like Sleeping Beauty," Schill concluded.

Schill and his team published their study findings and approach in the Journal of Zoology. Related information about how tardigrades survive extreme conditions is shown on Frankenscience's YouTube video below:

 

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