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The most indestructible creature in the world has become even more indestructible.
Not content with his existing abilities to survive extreme temperatures, pressures, and the airless vacuum of space, the humble but seemingly impossible-to-kill tardigrade seems to have unlocked another astonishing superpower: the ability to withstand lethal doses of ultraviolet (UV) radiation.
While we have previously observed that tardigrades survived radiation thanks to a ‘damage suppression’ protein called Dsup, this UV resistance trick is a recently identified feather on the tardigrade’s cap, which operates through a different kind of biological mechanism.
In a new study, scientists from the Indian Institute of Science detail the discovery of Paramacrobiotus sp. BLR, a strain of the genus Paramacrobiotus, belonging to the eutardigrada class.
Eutardigrades comprise the largest class of tardigrades; They are thick-looking with reduced lateral appendages (the parts that look like arms and legs).
The isolated team Paramacrobiotus BLR of a moss sample growing on a concrete wall in Bengaluru, India, and in subsequent experiments, subjected tardigrades to ultraviolet radiation emitted by a germicidal lamp, used for sterilization purposes by killing bacteria and viruses.
Under these deadly rays Paramacrobiotus BLR literally glowed, demonstrating a form of natural fluorescence called autofluorescence. This type of fluorescence has been seen in many animals before, including parrots, chameleons, and frogs, although its purpose remains enigmatic.
“The functional importance of this phenomenon is not clear, although in parrots visual cues have been attributed to potential mates,” explain the researchers, led by first author and biochemist Harikumar R. Suma, in their article.
But Paramacrobiotus BLR did more than just glow under ultraviolet radiation. Most also tolerated the rays for up to an hour, resisting radiation damage.
A rival species, Hipslbio pattern – control tardigrades, so to speak, and a few neighboring roundworms (included in the mix just in case) weren’t so lucky, though.
According to the researchers, fluorescence is what really allows Paramacrobiotus BLR to resist radiation. In another experiment, the team extracted the aqueous fluorescent chemical from Paramacrobiotus BLR and covered H. pattern in that.
When sprayed with the sparkling extract, H. pattern she showed greater tolerance than when she wasn’t wearing her sunscreen
“This provides direct experimental demonstration of fluorescence photoprotection,” the authors conclude.
“The fluorescent compound forms a ‘shield’ against ultraviolet radiation that protects these tardigrades from its lethal effects. We speculate that Paramacrobiotus The BLR strain has probably developed this fluorescence mechanism to counteract the high UV radiation of tropical south India (UV index can go up to 10). “
Findings are reported in Biology lettering.
