Ronda Rousey thought she was tough. Holly Holm proved to be tougher. But if the next bout were to be held in outer space, neither one alone nor as a tag team would stand a chance against a tiny female named tardigrade. Tardi who?
Tardigrades, also known as water bears or moss piglets, are water-dwelling, eight-legged, segmented animals measuring no more than 1 mm in length. What the tardigrade lacks in size, it makes up for in toughness. They have been found living at an altitude of 18,000 feet in the Himalayas and at the bottom of the ocean; in hot springs and in Antarctica. They can be heated to 150 degrees C, frozen to near absolute zero and exposed to deadly amounts of radiation.
Still not convinced the tiny tardigrade is tough? In 2007, thousands of them were attached to the outside of a satellite and launched into space. When the satellite returned, it was still covered with living tardigrades and the really tough females even laid eggs that also hatched and survived.
What makes the tardigrade so tough? According to a new report in the Proceeding of the National Academy of Sciences, it’s a lot of foreign DNA – the most of any known species. Study co-authors Thomas Boothby and Bob Goldstein of the University of North Carolina at Chapel Hill found that 17.5 percent of the tardigrade’s DNA comes from other species. To put this in perspective, most animals have less than one percent foreign DNA.
Through a process called horizontal gene transfer, the tardigrades swap genetic material with bacteria, plants, fungi and a variety of microorganisms. The researchers believe this foreign DNA helps the tardigrades survive in extreme conditions by allowing them to repair damaged DNA using the foreign DNA to create newer and tougher genes.
Boothby says this discovery will force us to rethink the concept of a tree of life with genetic material passing from parents to offspring.
So instead of thinking of the tree of life, we can think about the web of life and genetic material crossing from branch to branch. So it's exciting. We are beginning to adjust our understanding of how evolution works.
And to think it all started with a tiny tardigrade who had to toughen up when other started calling it a “moss piglet.”