Tardigrades May Not Have Foreign DNA After All

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A new study has thrown cold water on the idea that tardigrades, segmented micro-critters just fractions of an inch long, have about 17 percent foreign DNA.

Late last year, a study in the Proceedings of the National Academy of Sciences suggested that approximately 1/6th of the DNA in tardigrades (also known as water bears) came largely from bacteria.

The news was exciting. Could these tiny, nearly indestructible creatures have the ability to reuse large quantities of DNA from other species?

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Maybe not. The new study, also published in the Proceedings of the National Academy of Sciences, has lowered the 17 percent figure, arguing instead that the tiny animal actually has less than 1 percent of its genes borrowed from other species.

The authors of the research, from the University of Edinburgh, say the earlier study’s figure of 17 percent was due almost wholly to undetected bacterial contamination of the gene sequencing data and not to foreign DNA.

One percent, the scientists say, is not unusual.

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“We hope this paper will finally correct the scientific record,” said the study’s lead author Mark Blaxter, of the university’s school of biological sciences, in a statement. “Tardigrades are amazing organisms, but these suggestions about their DNA were a step too far, even for their eight legs.”

And tardigrades, no matter how much or how little foreign DNA, are indeed amazing. They can survive extreme temperatures and pressure, no food, radiation, and even trips to and from space unprotected. Some were recently “unfrozen” and revived after 30 years spent iced away in a moss sample stored at -20 C.

The durable creatures can be found in water (marine or fresh) as well as in soil, on mosses and lichens — basically all over the place, no matter the climate. Harder to kill than John McLane in a Die Hard film, tardigrades have even inspired architectural designs.

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