Tiny Water Bears, the World's Toughest Animal, Have a Bizarre Genome

One of the toughest creatures on Earth is the water bear, known formally as the tardigrade. Now, though, researchers have sequenced the genome of this tiny animal and have found that it gets a huge chunk of its genome from foreign DNA.

"We had no idea that an animal genome could be composed of so much foreign DNA," said Bob Goldstein, one of the researchers, in a news release. "We knew many animals acquire foreign genes, but we had no idea that it happens to this degree."

In this latest study, the researchers found that water bears get about 6,000 foreign genes primarily from bacteria, but also from plants, fungi and Archaea, through a process called horizontal gene transfer. This is the swapping of genetic material between species as opposed to inheriting DNA exclusively from parents.

Previously, another microscopic animal called the rotifer was the record-holder for having the most foreign DNA, but it has about half as much as the tardigrade. For comparison, most animals have less than one percent of their genome from foreign DNA.

"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," said Thomas Boothby, one of the researchers.

The scientists speculate that the DNA may be getting into the genome randomly, but what is being kept is what allows tardigrades to survive the harshest of environments. For example, a water bear can be kept in a -80 degree Celsius freezer for a year or 10 and can still be active about 20 minutes after thawing.

The findings are published in the journal Proceedings of the National Academy of Sciences.

Related Stories

Newly Discovered Gene Grows Sweeter, Well-Growing Tomatoes

Irish Potato Famine Pathogen Origins Tracked to South America with Ancient DNA

For more great science stories and general news, please visit our sister site, Headlines and Global News (HNGN).