Tardigrades are some of the most exceptional and curious creatures that exist. Since their discovery, biologists have been fascinated with their abilities: They can withstand the freezing cold of the Poles, the radiation of space, the scorching heat of a volcano, and extreme drought. Now, scientists have discovered that they stop aging when they are frozen, which means we are facing an authentic natural process of cryogenesis!
The science and other stuff to know
These small animals measure less than a millimeter and are also called “water bears.” They populate an astonishing variety of ecosystems and display a capacity for adaptation and survival that seems straight out of a science fiction movie. A study recently published in the Journal of Zoology accounts for this finding: Tardigrades not only survive but also do not age when frozen. Once thawed, all of their biological functions resume without injury or negative consequences.
In their article, the authors explained how this is possible: “To resist freezing, they enter cryobiosis, a state of biological organization in which metabolic activity is reversibly slowed down or stopped. Thus, cryobiosis resembles anhydrobiosis, where tardigrades (and some other invertebrate groups) suffer extreme desiccation and appear not to age in the dry state.”
Researchers already knew that tardigrades can withstand drought for years without dying of thirst. Faced with the scarcity of water, these animals become dehydrated: their body is completely devoid of moisture and this is how they manage to conserve themselves. Experts call this mechanism the “Sleeping Beauty model.”
To find out if this survival model also applies to when they experience a freezing period, a team of researchers from the University of Stuttgart conducted an experiment: More than 500 tardigrades were frozen at -30°C (-22°F), then thawed, counted, fed, and frozen again. The scientists did this until all of the animals died. Simultaneously, control groups were kept at a constant room temperature.
The results were surprising: Excluding the time spent frozen, the comparison with the control groups revealed nearly identical lifetimes.
Understanding how tardigrades’ biological mechanisms allow them to withstand extreme conditions could provide us with tools to search for signs of alien life beyond Earth. Could tardigrades, for example, withstand the conditions on moons and planets whose environments are so hostile that no life appears to be capable of inhabiting them?
We could also find a way to reproduce its mechanisms in the laboratory to delay the deterioration of human cells. This could potentially allow us to develop treatments for everything from degenerative diseases to aesthetic procedures.
Much remains to be understood about the mechanics of life. As far as we know, it always finds a clever and subtle way to preserve itself. Biologists are always looking for clues to develop models to improve people’s quality of life based on what they’ve learned about its mysterious and fascinating nature.