Scientists discover a new water bear species that fluoresce

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Tardigrades (also called water bears) are microscopic creatures that can withstand extreme environmental stress and can even survive radiations in outer space. Now a group of scientists at the Indian Institute of Science (Bengaluru) reported in Biology Letters that some tardigrade species use fluorescence to thwart lethal doses of UV that would otherwise kill many viruses or bacteria.

Scientists serendipitously identified this new reddish-brown species – Paramacrobiotus BLR strain – when they were gauging different tardigrades collected from moss samples grown on a wall in Bengaluru. When they exposed all the tardigrades with 1 kilojoule per square meter of UV for 15minutes, most of the Hypsibius tardigrade species died in 24 hours, but the Paramacrobiotus species survived. Not just that, when they exposed the Paramacrobiotus with four times more UV, 60% survived even after 30 days.

Surprised, they investigated further into what supports Paramacrobiotus survival. When they looked at all the tardigrades under an inverted fluorescence microscope, they found that Paramacrobiotus species fluoresce more than Hypsibius, and this fluorescence increased with exposure to UV.

Scientists then extracted the fluorescing material from Paramacrobiotus to coat the Hypsibius and several other worms (Caenorhabditis elegans). They found that the fluorescence coat shields the Hypsibius species and worms from lethal doses of UV that survived twice than their uncoated peers.

Like the way banks use a UV lamp to detect fluorescent number strip as a security feature of currency, these new species of tardigrades could have evolved to bank on fluorescence as their natural security.