Tardigrades , tiny aquatic creatures known as water bears , are particularly tough – they can survive extreme heat, radiation, and even the vacuum of outer space.
Now we must add one more resistance: a new species of tardigrade that can withstand ultraviolet (UV) light at such a lethal level that it is the one used to get rid of difficult-to-kill viruses and bacteria.
The discovery of this new species is the result of serendipity, that is, chance: researchers from the Indian Institute of Science searched their campus for water bears and then exposed them to different extreme conditions. They had a germicidal UV lamp in the lab, and they tested it .
The dose of 1 kilojoule per square meter, which killed the bacteria and intestinal worms after five minutes of exposure, was lethal for the tardigrades of Hypsibius exelaris at 15 minutes; most died after 24 hours. But when they hit a strange reddish-brown species with the same dose, it survived.
What’s more, when the researchers increased the dose fourfold, about 60% of the reddish brown bears lived longer than 30 days .
The researchers realized that they had found a new species of tardigrade, part of the genus Paramacrobiotus .
As it does? Fluorescent pigments, likely located under the skin of tardigrades, transform ultraviolet light into harmless blue light, the team reports in the journal Biology Letters .
The researchers then extracted the fluorescent pigments and used them to coat H. exelaris and various Caenorhabditis elegans earthworms. Thanks to this new shield, they survived almost twice as much as the animals without the shields .
It is likely, according to the researchers, that tardigrades developed fluorescence as a means of tolerating the high doses of ultraviolet rays typical of hot summer days in southern India.