Tardigrads are renowned for their ability to withstand harsh environmental conditions, and new research reveals the secret to the creatures’ incredible powers of endurance. When frozen, so-called water bears enter a state of “cryobiosis” and stop aging completely until thawed.
Such a finding builds on previous research that showed that late tissues undergo a similar process called anhydrobiosis when they encounter extremely dry conditions. This amazing ability to completely shut down their metabolism until conditions become more favorable has characterized the “Sleeping Beauty” hypothesis in relation to the fairy tale princess who spends a century in suspended animation.
Instead of kissing their late piglets, however, the study authors chose to continuously freeze and thaw the moss piglets to observe how this affected their lifespan. A total of 716 sloths participated in the study, with some acting as controls by remaining in a warm environment while others were subjected to sub-zero temperatures.
Those in the experimental group were frozen to -30°C (-22°F) for a week at a time, before spending a week at a more comfortable 20°C (68°F). This alternating weekly treatment was continued until all samples naturally reached the end of their life cycle.
“The snap-frozen lates lived twice as long as the control group, but both the control and snap-frozen groups had similar life spans if the time spent in the freezer was excluded,” the study authors explain. “This represents the first evidence that the ‘Sleeping Beauty’ hypothesis applies to cryobiosis, meaning that lateans do not age when frozen.”
Among those that were continuously frozen and thawed, the longest-lived lager survived for a total of 169 days, of which 75 were spent in cryobiosis and 94 in normal temperature. Similarly, the oldest late in the control group lived for 93 days, indicating how the animals seem to stop aging completely when frozen.
While it is unknown whether a tarantula could survive indefinitely in sub-zero temperatures, a study published in 2016 showed that the animals could successfully revive after being frozen for more than 30 years. Similar properties have been observed in other microscopic organisms called rotifers, one of which scientists revived after 24,000 years in the permafrost of Siberia.
Describing the concept of cryolife in the simplest possible terms, study author Ralph Schill explained in a statement that “during periods of inactivity, the internal clock stops and only resumes when the organism is reactivated.”
“Therefore, latecomers, which normally only live for a few months without periods of rest, can live for many years or even decades.”
The study was published in the Journal of Zoology.