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>
A completely unexpected discovery beneath the ice.
- Scientists find remains of a tardigrade and crustaceans in a deep, frozen Antarctic lake.
- The creatures' origin is unknown, and further study is ongoing.
- Biology speaks up about Antarctica's history.
Welcome to Subglacial Lake Mercer<p> The scientists were drilling in Subglacial Lake Mercer, a frozen body of water undisturbed for millennia. SALSA's is the first direct sampling of its contents. Prior to the drilling, it had only been examined with ice-penetrating radar and some other indirect detection devices.</p>
Boring details<p>SALSA drilled down a kilometer into the ice above Lake Mercer using a hot-water drill . At its maximum width, the hole was just 60 centimeters across.</p><p>On December 30, the team retrieved a temperature sensor from the frozen lake and noticed some gray-brown mud stuck to the bottom of it. Looking at the mud under a microscope, Harwood saw the glassy remains of photosynthetic diatoms, which he expected, but also a shrimp-like crustacean shell with its legs still intact. And then another, even better-preserved one.</p><p>To double-check, the team cleaned off their sensor and sent it down for more mud. This time, more crustacean shells and some other things that looked a bit like worms appeared under the microscope. On January 8, at a National Science Foundation base 900 kilometers away, animal ecologist named Byron Adams had a look. He confirmed the crustaceans, found the tardigrade, and identified the worm-like organisms as being thread-like plants or fungi. He'd seen all three types of creatures previously in the glacier-free <a href="http://icestories.exploratorium.edu/dispatches/big-ideas/dry-valleys/index.html" target="_blank" data-vivaldi-spatnav-clickable="1">Dry Valleys</a> of Antarctica, as well as in the <a href="https://www.nasa.gov/content/view-of-the-transantarctic-mountains" target="_blank" data-vivaldi-spatnav-clickable="1">Transantarctic Mountains</a>.</p>
Where the organisms were found, but why?<p>The animals could have come from other places, such as the ocean. Between five and ten thousand years ago, the Antarctic ice sheet became thinner for a while, and this could have allowed seawater to make its way beneath floating ice, carrying organisms along with it that eventually became trapped beneath the ice sheet when it returned to its normal thickness.</p><p>The water sampled from Lake Mercer has enough oxygen to sustain life, and is packed with bacteria, over 10,000 cells per millimeter. Harwood wonders if larger animals could have survived feeding on them, though the majority of biologists don't think it's likely to have been a substantial enough food source.</p><p>Adams suspects the creatures actually lived in the Transantarctic Mountains and were then transported after dying down to Lake Mercer. He says they seem too recent to have been neighbors of the millions-of-years-old diatoms. "What was sort of stunning about the stuff from Lake Mercer," Adams tells Nature, "is it's not super, super-old. They've not been dead that long." The eight-legged tardigrade from Lake Mercer resembles those found in damp soil, reinforcing Adam's conclusion.</p>
Back to the lab<p> The next steps for these intriguing remains is an attempt at determine their age using radiocarbon dating. In addition, researchers will try and sequence DNA scraps from them to learn if they're of marine or freshwater species. Finally, scientists will perform chemical analyses of carbon the remains contain to see if a determination can be made as to whether the animals spent their days in sunlight or in the dark, far beneath the Antarctic.</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.