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The new fluorescent tardigrade withstands lethal doses of radiation

A tardigrade just described glows blue under UV light.

A tardigrade just described glows blue under UV light.
Image: H R. Suma et al., 2020 / Biology Letters

A kind of newly discovered tardigrade that shines blue when exposed to ultraviolet light it uses the powers of fluorescence as a protective shield, according to new research.

Tardigrades, nicknamed aquatic bears or mossy pigs, we are microscopic animals able to tolerant some incredibly difficult conditions, such as freezing temperatures, radiation, dehydration and even the vacuum of space. In 2016, scientists in Japan even managed to do this relive a tardigrade that had been frozen for more than 30 years. About 1,300 different species of these eight-legged creatures they are known to exist and are found all over the world.

Indian scientists have discovered another tardigrade superpower, at least in one particular species. These previously unknown tardigrades, assigned to Paramacrobiotus typically, it exhibits a natural fluorescence, casting an eerie blue glow when exposed to ultraviolet light. Furthermore, and as the authors of the new study argue, this fluorescence protects tardigrades from UV radiation levels known to kill other microorganisms, such as bacteria and viruses. The new paper, published today in Biology Letters, was co-authored by biochemist Sandeep Eswarappa of the Indian Institute of Science in Bangalore.

Eswarappa and his colleagues rolled the new tardigrade and other from the moss growing on a concrete wall in Bangalore. Using a germicidal lamp, the scientists detonated the samples with ultraviolet light, which was done to test the creatures’ tolerances. Fifteen-minimal doses delivered at 1 kilojoule per square meter wiped out most individuals from a tardigrade species known as Hypsibius examplesand all were dead after 24 hours.

Strangely, however, a mysterious group of tardigrades with reddish-brown spots managed to survive for 30 days after a dosage that kills bacteria and nematode worms (Caenorhabditis elegans) in just five minutes. In a follow-up test, Eswarappa and his colleagues increased the dose to 4 kilojoules per square meter, and this time for a full hour. Incredibly, 60% of the strange tardigrades managed to survive for 30 days after this intense exposure. At this point, it was clear that scientists had stumbled upon a new species, which they tentatively assigned as Paramacrobiotus BLR.

“After UV radiation treatment, tardigrades were observed daily for signs of life – active movement and egg-laying,” the study authors wrote. “There was no significant change in the number of eggs laid, their hatchability and hatching time between UV-treated and untreated. Paramacrobiotus BLR samples. “

The next step involved an investigation of the tardigrades with an inverted fluorescence microscope, which caused the reddish-brown tardigrades to project blue light. The scientists, thinking that the fluorescent skin pigments of tardigrades could be linked to UV resistance, performed an interesting experiment: they covered H. examples samples, along with some nematode worms, with the pigments, and once again exposed them to the UV lamp. The resulting fluorescent compound formed a “shield” that helped these organisms survive at nearly double the rates of unprotected cohorts.

Consequently, the new study shows that “it is possible to transfer the UV tolerance property from Paramacrobiotus UV sensitive BLR strain H. examplesself C. elegans using the fluorescent extract, “wrote the authors, adding that this provides a” direct experimental demonstration of photoprotection by fluorescence “.

Illustration for the article titled The newly discovered glowing tardigrade is strangely resistant to lethal doses of UV radiation

Organisms have all kinds of strategies to protect yourself from UV rays, such as DNA repair mechanisms and compounds that absorb UV rays (melanin in mammals is a good example). Scientists suspected that the fluorescence might impart a similar effect between corals and scallop jellies, but there was no experimental evidence.

The exact mechanism of protection remains unknown, but Eswarappa’s team suspects the fluorescent screen absorbs harmful UV radiation and emits harmless blue light. Paramacrobiotus BLR probably developed this special trick to protect itself from the high UV radiation found in tropical South India, where the UV index can reach 10, according to the authors.

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