Tardigrades: Water Bears Evolved To Survive Lethal UV Radiation Using Fluorescent Shield

Tardigrades can survive Extreme Conditions

Conditions like radiation and extreme heat, where most of the animals can get killed, is not a problem for Tardigrades, small aquatic creatures known as water bears, as it can survive those conditions that most animals cannot, even it can survive the vacuum of outer space. Now new findings are witnessed that the new species of tardigrade can now endure to Ultraviolet (UV) light that is as lethal as they are often used to get rid of hard to kill bacteria and viruses.

Survival to UV light

The researchers at the Indian Institute of Science discovered by chance as they scoured their campus for water bears and then they were exposed to extreme conditions. So for instance they happened to have a germicidal UV lamp in the lab, used to get rid of hard to kill bacteria and viruses, so they decided to test their specimen with the UV lamp.

Although all the species of tardigrades are not immune to UV light as a dose of 1 kilojoule per square meter, which killed bacteria and roundworms after just 5 minutes, was lethal to Hypsibius exemplaris tardigrades at 15 minutes and within 24 hours all the specimen died. On another and when with the same dose they hit a strange, reddish-brown species, all of them survived. While when the researchers increased the dose four times, life expectancy increased by 30 days among 60% of reddish-brown bears.

UV light converted to Blue Light

So this research gave the realization to the researchers that they found a new species of tardigrade, which is part of the Paramacrobiotus genus. To figure out how the new species survived the UV light exposure, even though they were found living in moss on a concrete wall in Bengaluru, India, the scientists examined it with an inverted fluorescence microscope. The reddish tardigrades became blue as they went under the UV light which was a surprise to the researchers.

This transformation by the exposure of UV light was possible due to the fluorescent pigments that transformed UV light into harmless blue light as per the reports of the team in Biology Letters. And the species with less pigment, Paramacrobiotus, died about 20 days after the exposure.

How was this possible?

Now the researchers took a step ahead by extracting the fluorescent pigments and used them to coat H. exemplaris and several Caenorhabditis Elegans earthworms. So the experiment deduced that the animals without the jury-rigged shields survived almost half the time in comparison to the ones having the shields. This is quite possible that due to the hot summer days in southern India the tardigrades evolved fluorescence as a means to tolerate the high doses of UV in that season.