The tiny tardigrade is the only animal to survive the conditions of outer space, and shocking new research suggests a huge chunk of their genome comes from foreign DNA.
A team of researchers sequenced the tardigrade's genome, and discovered it consists of 17.5 percent foreign DNA, the University of North Carolina at Chapel Hill reported.
"We had no idea that an animal genome could be composed of so much foreign DNA," said co-author Bob Goldstein, faculty in the biology department in UNC's College of Arts and Sciences. "We knew many animals acquire foreign genes, but we had no idea that it happens to this degree."
The tardigrades were found to have acquired about 6,000 foreign genes primarily from bacteria, plants, fungi and Archaea through a process called horizontal gene transfer. The findings could provide key insights into the link between foreign DNA and the ability to survive harsh conditions.
"Animals that can survive extreme stresses may be particularly prone to acquiring foreign genes-and bacterial genes might be better able to withstand stresses than animal ones," Boothby said.
Tardigrades can survive a year in a freezer, and starts running around 20 minutes after thawing. Researchers believe the critters survive these harsh conditions by breaking down their DNA into tiny pieces, and can repair them as they return to normal conditions.
"We think of the tree of life, with genetic material passing vertically from mom and dad," Boothby said. "But with horizontal gene transfer becoming more widely accepted and more well known, at least in certain organisms, it is beginning to change the way we think about evolution and inheritance of genetic material and the stability of genomes. 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."
The findings were published in a recent edition of the Proceedings of the National Academy of Scientists.