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The tardigrade, or water bear, is a microscopic water dweller which grows to about a millimeter on average. It is a weird little animal that can withstand temperatures near absolute zero as well as above the boiling point of water, can withstand incredible amounts of radiation, and can live without food and water for more than ten years. It is also the only animal known to be able to survive space’s harsh vacuum. In essence, this creature is nearly impossible to destroy, and now science has discovered that it’s DNA is as weird as the creature itself. Researchers have discovered that this little being boasts the most foreign genes of any other animal that has been mapped so far. In other words, 1/6 of it’s genome was stolen from other species. For those of us who are not DNA researchers, the process by which genes are borrowed from another organism, opposed to traditional reproduction, is called horizontal gene transfer. It has been known to occur occasionally in other animals, including humans, and it is more often than not the result of exchanging genes with viruses. To put things into perspective, most animals contain only 1% of foreign DNA. Research on the tardigrade found that about 6000 of its genes came from foreign species, or about 17.5% .

“We had no idea that an animal genome could be composed of so much foreign DNA,” said study co-author Bob Goldstein from the University of North Carolina at Chapel Hill to – “We knew many animals acquire foreign genes, but we had no idea that it happens to this degree.” This begs the question of where the genes came from. The answer is that it is likely primarily bacteria, but is also derived somewhat from plants and fungi. It is this variety of genes that scientists think allows the tardigrade such extreme survival capacity. “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 researcher Thomas Boothby. The jury is out as to exactly how the creature has borrowed the foreign genes, but the researchers hypothesized that it is due to another odd survival mechanism: the tardigrade can dry out until its body is comprised of only 3% water, then bounce back. When this happens, the DNA is broken down into small segments. While rehydrating, the nucleus of the cells become leaky, allowing other molecules and DNA to pass through As such, the DNA acquisition would be a random process. But it is thought that this is in line with evolution, and genes that help survival get passed down through reproduction. What’s exciting is that this process provides insights into the evolution of life. Boothby is quoted: “We think of the tree of life, with genetic material passing vertically from mom and dad. 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. Instead of thinking of the tree of life, we can think about the web of life and genetic material crossing from branch to branch … it’s exciting. We are beginning to adjust our understanding of how evolution works.” The research has been published in the Proceedings of the National Academy of Sciences, and will provide useful insight into the development of medicine. Thanks, water bear ( via )!