A tiny tardigrade can survive intense ultraviolet radiation for an hour by glowing in the dark. “It acts like a shield,” says Sandeep Eswarappa at the Indian Institute of Science in Bangalore.
Tardigrades, also known as water bears, are animals around 1 millimetre long. They are famous for being able to withstand extreme conditions that would kill most organisms, such as being completely dried out.
Studying moss at their institute’s campus, Eswarappa and his colleagues found what may be a new species of tardigrade, though they don’t yet have enough information to formally describe it. For now, they are calling it Paramacrobiotus BLR, short for Bangalore.
“We found this particular tardigrade in many places, especially in places that are well lit with sunlight,” says Eswarappa. The researchers transferred some of the animals to their laboratory and began to study them.
Their first experiment involved exposing the animals to a germicidal ultraviolet lamp. A control animal, a worm called Caenorhabditis elegans, died within 5 minutes, but Paramacrobiotus BLR survived for an hour.
“The next step happened serendipitously,” says Eswarappa. While looking at how the tardigrades might survive the UV light, he left a tube of them near a UV source and noticed that the tube started glowing.
Further experiments revealed that the tardigrades contain a fluorescent chemical. “It is absorbing the UV light and emitting harmless visible light in the blue range,” says Eswarappa.
The team was able to transfer the fluorescent chemical to another tardigrade, Hypsibius exemplaris, and to C. elegans, both of which are sensitive to ultraviolet radiation. This protected them from 15 minutes of UV exposure.
The team doesn’t yet know exactly what makes up the fluorescent shield, as simple methods for identifying the chemicals haven’t yielded clear results. “It is not a simple compound,” says Eswarappa.
Once the chemical is known, Eswarappa hopes to make it in large quantities and to explore whether it might be used in sunscreen. “We’d like to patent it and see whether we can mass-produce [it],” he says.
Journal reference: Biology Letters, DOI: 10.1098/rsbl.2020.0391
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