This Newly-Discovered Tardigrade Species Can Handle Lethal UV Radiation

Tardigrades are known to be some of the hardiest creatures, and a team of researchers just found a new species that can even handle lethal amounts of ultraviolet (UV) light through fluorescence.

Tardigrades are perhaps some of the most interesting creatures on the planet. Also known as water bears, they are extremophiles, which means they can survive in extreme environments. In 2019, for instance, it was reported that the tardigrades that were sent to the moon as part of ISRO's Beresheet mission possibly survived a lunar lander crash.

In a new study published in Biology Letters, a team of researchers from India reports the discovery of a new tardigrade species. Now part of the Paramacrobiotus genus, the new species reportedly glows blue under UV light and can even endure lethal doses of UV light that can quickly kill bacteria and viruses.

The new species was discovered in a moss sample collected from a concrete wall in Bengaluru, India. When the researchers exposed the specimen to extreme conditions using a germicidal UV light, the reddish-brown tardigrades survived a UV dose that killed bacteria in five minutes and Hypsibius exemplaris tardigrades in about 15 minutes. In fact, most of the H.exemplaris tardigrades were dead within 24 hours.

But even when the researchers increased the dose to four times, the reddish-brown tardigrades survived, with 60% of them even lasting for over 30 days without significant changes to their egg-laying behavior and hatching time.

When they examined the tardigrades under an inverted fluorescent microscope, they emitted blue light. This means the tardigrades were capable of fluorescence.

According to the researchers, it's possible that the tardigrades were not just simply glowing. Instead, their fluorescence is likely what helps them endure the lethal doses of UV light by absorbing the harmful radiation and transforming it into blue light.

To test their hypothesis, the researchers covered H. exemplaris and some nematodes with the fluorescent extract from the new species and it indeed provided them better protection from the UV radiation.

"This provides the direct experimental demonstration of photoprotection by fluorescence," the researchers wrote. "The fluorescent compound forms a 'shield' against UV radiation, protecting these tardigrades from its lethal effects."

It's possible, the researchers said, that the species evolved this trait while adaptating to the "high UV radiation" that is typical during summer days in southern India.