Tardigrades are some of the toughest animals on the planet. These microscopic creatures commonly called “water bears” can survive in environments with extreme temperatures, without water or oxygen. Scientists may have pinpointed the precise molecular mechanism the tiny invertebrates use to put up with such intense conditions. They have a molecular sensor that detects uninhabitable elements of their environment, and tells them when to go dormant and when to resume their normal activities. The findings are described in a study published January 17 in the open-access journal PLOS ONE.
[Related: Tardigrades go where the slime takes them.]
What is a tardigrade?
There are more than 1,100 species of tardigrade. These free-living invertebrates are considered close relatives of arthropods. They are about 0.04 inch or less in size and live in a variety of habitats. They are found on flowering plants, in moss, sand, fresh water, and the ocean.
Most plant-eating tardigrades pierce individual plant cells with their stylets and suck out the cell’s contents for sustenance. Some are predatory carnivores that eat other small invertebrates.
German zoologist J.A.E. Goeze saw tardigrades through a microscope in 1773 and recorded that its body looked like a shriveled and shrunken version of a bear. He named it kleiner Wasserbär, or German for “little water bear.”
How do they survive extreme environments?
When faced with dry, barren, and otherwise inhospitable environments, tardigrades go dormant and enter a tun state. Their eight legs retract, their bodies become dehydrated, and their metabolism slows down so much that it is almost undetectable. They curl up into a ball. They can remain in this state for years. Previously, scientists weren’t sure what signals water bears to enter or leave their death-like state where they don’t require nutrients.
In this new study, researchers exposed the tardigrades to temperatures of -112…
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