Spoiler alert: Water bears do not have extensive foreign DNA
Tardigrades, they are cute and cuddly — okay maybe not cuddly — but they have earned their nicknames, such as moss piglets or water bears. Mostly because they look like, well bears (although I don’t see a piglet personally). These guys are eight-legged microscopic animals that have long fascinated scientists for their ability to survive extremes of temperature, pressure, lack of oxygen, and even radiation exposure. Talk about a thrill seeker they can even survive in space, without a suit, where were humans when they were handing out those genes?
Even more exciting, back in November 2015 a study suggested that 17 percent of their DNA was foreign, as in from other species. This announcement lead people to think that maybe we missed out on the spacefaring genes because our little water bear was mashing all sorts of DNA together to see what they could do with it. Mashing being the scientific term for horizontal gene transfer — or maybe it’s the other way around.
There was excitement, there was joy, and someone even cried — maybe. Heck, there’s even a horror movie about the little guys doing sucking up genes like they were food, which actually predates the study. Leaving you to wonder if they saw the movie and thought, “Hey, that would be a cool idea to test.”
But let’s face it, nature has a way of dashing our Hollywood-esque horror movie dreams. Which in this case may be a good thing if you look at it from the movie outcome. Soon after the study was published, a new team from Edinburgh used DNA sequence data from the same species and found that almost all of the proposed foreign DNA was in fact contamination. A plot twist that even the most optimistic of scientists saw coming, unfortunately.
So the original team went back and in their latest study, they conducted careful analysis of both sets of data using new computational tools. Their findings suggest that less than 1 percent of tardigrades’ genes are likely to have been borrowed from other species. This number is unsurprising – even humans have a few borrowed genes, like viral genes.
“What would in decades past have taken many months to sort out became the focus of experts around the world and has been swiftly resolved. We hope this paper will finally correct the scientific record. Tardigrades are amazing organisms, but these suggestions about their DNA were a step too far, even for their eight legs,” Professor Mark Blaxter, led of the study, said.
Despite the findings, tardigrades are still pretty impressive, like surviving 30 years frozen and still able to reproduce. If that isn’t enough, how about that when they dry out they turn to glass, are still able to be rehydrated and carry on like it was nothing. Heck I would just be happy with the surviving in space genes, but I’m sure being able to dry out would come in handy… someday… okay maybe not for us humans. Still pretty impressive party trick when the water bear does it.
Now you’re probably wondering, “Wow, this guy really likes these little water bear things. I wonder if he has a giant plush tardigrade next to his bed.” If you weren’t wondering, you might be now, and even if you couldn’t care less, the answer is yes, yes I do and so can you!
Georgios Koutsovoulosa, Sujai Kumara, Dominik R. Laetsch, Lewis Stevens, Jennifer Daub Claire Conlon, Habib Maroon, Fran Thomasa, Aziz A. Aboobakerc, and Mark Blaxter (2016). No evidence for extensive horizontal gene transfer in the genome of the tardigrade Hypsibius dujardini PNAS DOI: 10.1101/033464