Tardigrades are quite good at adjusting to challenging environmental circumstances. In the past, Ralph Schill, a professor at the University of Stuttgart's Institute of Biomaterials and Biomolecular Systems, showed that dried tardigrades might remain unharmed for several years without ingesting water.

The Journal of Zoology reported the research and methodology used by Schill and his associates.

Understanding Tardigrades

It was previously unknown whether they mature more quickly or slowly in a frozen condition or if aging stops altogether. But the riddle is now clear: tardigrades that have been frozen do not age.

Tardigrades sometimes referred to as water bears, are nematodes. There is only one resemblance between them and bears in their walk. The tardigrades, which are only one millimeter long, have fully evolved to adapt to quickly changing climatic circumstances and may dry out in scorching temperatures and freeze in frigid ones. Schill argues, "They don't die; they go into a profound sleep.

A protein known as Dsup (for Damage suppression protein), which is unique to tardigrades, was discovered in earlier investigations. Intriguingly, when tested in these cells, Dsup can shield human cells from X-rays, but it wasn't understood how Dsup does this remarkable accomplishment. The UC San Diego scientists found through scientific investigation that Dsup interacts with chromatin, the type of DNA found inside cells. Dsup defends cells after it is attached to chromatin by creating a shielding cloud that shelters DNA from hydroxyl radicals created by X-rays.

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Going to the Extremes

Different types of stress might result from the freezing or drying out of a cell organism. However, tardigrades are unaffected by either extreme heat or cold. They no longer exhibit any recognizable life signals. It also asks what happens to the animals' internal clocks while resting and if they age.

Ralph Schill and his team provided a remedy to the aging conundrum for dry tardigrades, which spend several years in their environment waiting for the next rain. The princess in a Grimm Brothers' fairytale passes out and sleeps well. One hundred years later, she is kissed by a prince, and when she awakens, she still has the same youthful beauty. This theory is sometimes referred to as the "Sleeping Beauty" hypothesis since it holds for tardigrades in a dried state ("Sleeping Beauty" model).

According to Schill, the internal clock halts during inactivity and only starts up again when the organism is revived. Therefore, tardigrades can survive for several years or even decades, typically only having short lifespans of a few months without rest.

Need More Study

It had not yet been determined whether this also applied to animals that were frozen. Do they mature more quickly or slowly than the dried animals, or does aging stop altogether?

Schill and his colleagues performed several tests in which they froze more than 500 tardigrades at -30 °C, thawed them out again, numbered them, fed them, and then froze them once again to investigate this. Until all of the animals perished, this was repeated. Control groups were kept at a steady room temperature at the same time. The comparison with the control groups indicated an essentially equal lifespan when the time spent in the frozen state was excluded. Schill says, "Tardigrades thus halt their internal clocks like Sleeping Beauty even in ice.

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