Another amazing tardigrade survival skill is discovered.
- Apparently, some water bears can even beat extreme UV light.
- It may be an adaptation to the summer heat in India.
- Special under-skin pigments neutralize harmful rays.
Stressor testing<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDU1MzIzMS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyMjc2MDc4Mn0.5R6DAfzsq29zvETCEH1sR9rprcnJv_L0KyUW2qedslE/img.jpg?width=980" id="c6b71" class="rm-shortcode" data-rm-shortcode-id="e7afe644fc94631ed9ea6837ed3920d3" data-rm-shortcode-name="rebelmouse-image" alt="water bear illustration" />
3D illustration of a tardigrade
Credit: Dotted Yeti/Shutterstock<p>It seems at times like scientists enjoy playing the "let's see if <em>this</em> kills them" game with tardigrades, a game that humans usually lose. After searching the campus of the Indian Institute of Science, researchers gathered some water bears and brought them back to the lab to see what they could handle.</p><p>The scientists found that after they exposed <a href="http://cshprotocols.cshlp.org/content/2018/11/pdb.emo102301.full" target="_blank"><em>Hypsibius exemplaris</em></a> tardigrades to very high doses — 1 kilojoule (kJ) per square meter — of UV light for about 15 minutes, they would in fact die over the next 24 hours. However, when they aimed the same blasts at the reddish-brown tardigrades…nothing. The humans even quadrupled the UV intensity and, nope, they tracked the water bears for 30 days, and a majority of them, 60 percent, were still fine.</p><p>As is often the case with tardigrades, the question is how?</p>
Turning deadly light blue<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDU1MzIwMy9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxMTM1NTE2N30.n8FiCLgp5aTqmYby2bjpeu9QJRTV7KzaB9tmTHBzWtk/img.jpg?width=980" id="5d4cc" class="rm-shortcode" data-rm-shortcode-id="7aa8735a958123bcfb269920eb4d2aed" data-rm-shortcode-name="rebelmouse-image" />
Tardigrade's normal appearance (left), and under inverted fluorescence (right)
Credit: Suma et al., Biology Letters (2020)<p>When the researchers examined the tardigrades under an inverted fluorescence microscope they found that when they were exposed to UV light, they became blue. The researchers' hypothesis is that these tardigrades carry fluorescent pigments beneath their skin that they deploy as necessary to transform UV light into simple benign, blue light. It may be that this ability has emerged as an evolutionary response to southern tropical India's often-extreme heat. The study says that typical summer-day UV levels in this region are about 4kJ per square meter.</p><p>Of the 40 percent of the reddish-brown tardigrades that had died before 30 days — mostly after about 20 days — the scientists concluded they had less pigment with which to neutralize UV light.</p><p>When the scientists extracted the pigment from the UV champions and coated some <em>Hypsibius exemplaris</em> tardigrades with the stuff, their resistance to UV exposure was also enhanced, boosting their survival rate to almost twice that of their uncoated brethren.</p><p>Autofluorescence has been found in other animals — parrots, scorpions, chameleons, and frogs, among others — so it's not completely unheard of. In parrots, for example, autofluorescence is hypothesized to be involved in tweaking coloration during mating rituals. Still, surprise, tardigrades seem to be putting it to unusual use by employing it for UV protection. </p>
Freeze it, boil it, or expose it to radiation. The water bear shrugs it off. Now we know why.
The tardigrade, also known as the moss piglet or water bear, is a bizarre, microscopic creature that looks like something out of a Disney nightmare scene: strange but not particularly threatening. The pudgy, eight-legged, water-borne creature appears to be perpetually puckering. It's the farthest thing from what you'd expect an unstoppable organism to look like.