Tardigrades have always been known for their toughness, but now it seems they might be able to share a superpower.
Sometimes known as water bears, these micro-organisms are found everywhere from Antarctica to volcanic vents and can survive conditions that would ordinarily be lethal, including extreme cold, heat pressure and lack of air. They even thrive in space.
Now a study by biochemists at the Indian Institute of Science suggests some tardigrades also have a blue fluorescent layer that protects them from harmful UV radiation. And this fluorescence may be transferable.
In a paper in the journal Biology Letters, the researchers describe exposing tardigrade species from the Paramacrobiotus genus to high bouts of UV for up to an hour. They were unaffected, and other parts of their egg-laying cycle were unharmed: but a control species died quickly after exposure.
The “fluorescent compound forms a ‘shield’ against UV radiation protecting these tardigrades from its lethal effects”, Sandeep Eswarappa and colleagues write.
They suggest this genus of tardigrades evolved to be more resistant to UV because it adapted to areas of India that were frequently exposed to intense sunlight. Those that were not as well protected were more likely to live in mossier areas where they could hide.
To see if the “shield” could be applied to other organisms, they then extracted the protective pigment from tardigrades and submerged the nematode C. elegans into the solution. Surprisingly, they were able to survive radiation better than they normally would.
Photoprotection may be why some animals, like jellies, are fluorescent. UV radiation damages cellular chemical processes and leads to oxidative stress, but fluorescent photoprotection could prevent this damage by conferring the radiation.
This is one of the first times photoprotection has been demonstrated, the researchers say, and it is all thanks to the special blue pigment.
What makes this study so interesting is that they were able to transfer the pigment to a completely different organism and grant the nematodes better photoprotection. This is a demonstrated example of fluorescent pigment directly causing, not only protection, but transferable protection from UV.
Deborah Devis is a science journalist at Cosmos. She has a Bachelor of Liberal Arts and Science (Honours) in biology and philosophy from the University of Sydney, and a PhD in plant molecular genetics from the University of Adelaide.
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