From Popular Mechanics
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New research suggests tardigrades have a very surprising vulnerability considering their well-known toughness.
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A study published in Scientific Reports reveals that tardigrades seem highly susceptible to prolonged exposure to high temperatures possibly because some of the proteins that keep their bodies alive during tun state become denatured.
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The team behind the study hopes that their findings will lead to additional research on temperature tolerance for the creatures.
Turns out tardigrades—the toughest animals on Earth—have a weakness after all and it’s pretty surprising for a species known to survive in the vacuum of space.
So what is this robust creature’s Achilles heal? Lots of Heat.
According to a study published in Scientific Reports, prolonged exposure to heat—ranging from 99 to 181 degrees Fahrenheit—results in a high mortality rate for Ramazzottius varieornatus, a species of tardigrade (of which more than a thousand exist). For their study, researchers analyzed active and desiccated tardigrades across a timespans ranging between one and 48 hours.
Desiccation is when tardigrades expel the water from their bodies, tuck their legs under them, and roll up into a little ball called a tun. They can live in a desiccated state for decades and don’t age while in this state. Essentially, desiccation for tardigrades is like pushing a pause button—they’re existing but not really living.
The results show about a 50 percent mortality rate in active tardigrades who only had an hour to acclimate to 99 degree Fahrenheit. According to the study, “metabolically active tardigrades are vulnerable to high temperatures, yet acclimatization could provide a tolerance increase.”
A tardigrade in a desiccated state fares much better with a 50 percent mortality rate up to 181 degrees Fahrenheit during 1 hour of exposure, but that heat threshold drops to 145 degrees Fahrenheit when exposed for 24 hours.
Finding the tardigrade’s weakness wasn’t easy as these micro-animals have lived through five mass extinctions. According to a 2017 study, the only way to kill them off would be boiling all the water in the Earth’s oceans.
The researchers note that certain “bioprotectants,” such as disaccharides, work to stabilize proteins, acids, and lipids within tardigrades in conjunction with heat protectant proteins that keep the creatures alive while in tun form and also work to bring them back from desiccation.
The study suggests that when tardigrades are exposed to high temperatures, some of those proteins become destabilized and denatured, putting the organism in peril. It also suggests that tardigrades may not survive in a continually warming climate as the creatures are more sensitive to warm temperature fluctuations than previously believed.
The team behind this study hopes that their work will lead to additional research and “provide new insights that would help understand their limits of tolerance more comprehensively.”
Studying tardigrades may also help us better understand the aging process. The microscopic animal can undergo cryptobiosis where its metabolism significantly slows to 0.01 percent of normal. This allows the tardigrade to enter a sort of stasis for extended periods. If humans had the ability to enter cryptobiosis—or create a similar process artificially—it could revolutionize life expectancy rates and help develop new strategies for deep space missions.
Tardigrades still remain a mystery, but it’s a mystery we’re slowly solving.
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