The State of Tun
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The minuscule tardigrades are one of the toughest animals on Earth, capable of surviving the vacuum of space and extreme temperatures.
Also known as “water bears,” they are around 0.04 of an inch in size, live in a variety of habitats and are considered close relatives to arthropods.
When exposed to inhospitable environments, tardigrades enter a dormant state – or “tun state” – that causes their metabolism to nearly grind to a halt, while their bodies become dehydrated.
And they can remain in that state for years without any food.
To determine how they activate this tun state, a research team exposed the invertebrates to a series of stressors, including -112 degrees Fahrenheit and high levels of hydrogen peroxide.
They noticed that the creatures’ cells produced oxygen free radicals – atoms or molecules that contain unpaired electrons – in response to these challenging conditions.
These free radicals would also oxidize with an amino acid called cysteine, which is one of the building blocks of proteins in the body. This oxidation causes the proteins to alter their functions and structure, as well as signal the tardigrade to go dormant.
The team explained that the cysteine allows the tardigrades to feel out of their environments and react to many stressors. This means that it also allows the water bears to survive in shifting environments.
The authors hope that future research into this mechanism and tardigrades could help scientists better understand aging.