Tardigrade genome sequences reveal mystery of amazing resilience

Brittany A. Roston - Jul 27, 2017
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Tardigrade genome sequences reveal mystery of amazing resilience

The tardigrade — or water bear, if you prefer — is an incredibly resilient micro animal capable of surviving conditions that would kill just about everything else on Earth. Research has found the microscopic animal is capable of surviving the radiation of space, freezing temperatures, dehydration, and much more; in fact, it is estimated that the tardigrade will outlive all apocalypses, surviving until the sun itself stops shining.

Of course, the discovery of this incredible durability ushered in questions of how it can survive in such extreme conditions. One unusual theory has been that the tardigrade is a sort of animal-bacteria hybrid, something based on questionable results from a past study. That’s not true, though, at least based on this latest study that sequenced the micro animal’s genome.

A tardigrade’s DNA doesn’t hold any surprises (like hybridization, that is), but does help shed light on how the creature can handle extreme conditions. One notable discovery is that tardigrades can handle being dehydrated, later reanimating once exposed to water, thanks to special proteins that replace the water removed from the animal’s cells.

These particular proteins serve as a protection for the cell structure, enabling it to persist until water has returned…even if that takes a very long time. The study goes on to explain that proteins are behind many of the animal’s abilities, though the extent of what the proteins make possible isn’t clear.

Meanwhile, the study also highlighted a new revelation about the tardigrade’s origins, indicating that it is most closely related to the ordinary nematode. This conclusion was made based on the fact that both tardigrades and nematodes are lacking the same five HOX genes, leaving them with only five rather than the ten or so typically found.

The study explains, on that latter note:

Using the improved genomes, we explored the evolutionary relationships of tardigrades and other molting animals, particularly nematodes and arthropods. We identified conflicting signals between sequence-based analyses, which found a relationship between tardigrades and nematodes, and analyses based on rare genomic changes, which tended to support the traditional tardigrade-arthropod link.

SOURCE: PLOS Biology


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