Scientists finally figure out why the water bear is nearly indestructible
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.
Yet, water bears can withstand even the vacuum of space, as one experiment showed. A sort of microscopic Rasputin, tardigrades have be frozen, boiled, exposed to extreme doses of radiation, and remarkably still survive. How they do this has been a mystery to science, until now.
Being a water-borne creature, scientists in this experiment examined how it survived desiccation, or being completely dried out. When it senses an oncoming dry period, the critter brings its head and limbs into its exoskeleton, making itself into a tiny ball. It'll stay that way, unmoving, until it's reintroduced into water.
It's this amazing ability that piqued Thomas Boothby's interest. He's a researcher at the University of North Carolina, Chapel Hill. Boothby told The New York Times, “They can remain like that in a dry state for years, even decades, and when you put them back in water, they revive within hours." After that, “They are running around again, they are eating, they are reproducing like nothing happened."
Originally, it was thought that the water bear employed a sugar called trehalose to shield its cells from damage. Brine shrimp (sea monkeys) and nematode worms use this sugar to protect against desiccation, through a process called anhydrobiosis. Those organisms produce enough of the sugar to make it 20% of their body weight.
Not the water bear. Trehalose only takes up about 2% of its entire system, when it's in stasis. Though employing a sugar to preserve one's body sounds strange, the newly discovered process that the water bear goes through is even more bizarre. It turns itself into glass.
In this study, tardigrades were placed into a drying-out chamber, which mimicked conditions the organisms would encounter in a disappearing pond. As the water bears underwent anhydrobiosis, scientists examined what genes were activated. These genes produced a certain protein, which they named tardigrade-specific intrinsically disordered proteins (TDPs).
When the genes which produce TDPs were blocked, the water bears died. “If you take those genes and put them into organisms like bacteria and yeast, which normally do not have these proteins, they actually become much more desiccation-tolerant," Boothby said.
Water bear under a microscope. Flickr.
It's when the drying out process begins that such genes are activated, flooding the water bear's system with the protective protein. The process occurs in much the same way as trehalose preserves sea monkeys, according to Boothby. This is an example of convergent evolution, when two unrelated organisms develop the same trait for survival.
Usually, proteins are formed in orderly, 3D chains of amino acids. But TDPs operate differently, in a kind of random, somewhat disorganized manner. Dr. Boothby said, “It's a really interesting question about how a protein without a defined three-dimensional structure can actually carry out its function in a cell." Another question, is this protein used by any other organisms?
When desiccation begins and TDP is activated, it engages a process known as vitrification. Boothby said, “The glass is coating the molecules inside of the tardigrade cells, keeping them intact." From there, it goes into a form of stasis until it detects water. When that occurs, the protein is dissolved into the liquid and the tardigrade is revived.
There could be some practical uses to this discovery. For instance in medicine, vaccines often require refrigeration. But in the developing world, it isn't always available, which makes delivering vaccines to vulnerable, rural communities difficult.
Dr. Boothby believes that we may be able to use TDP to sort of freeze-dry vaccines or medications, for easy storage and transport. What about putting humans in stasis for space travel or when they have terminal diseases, to await a cure? No word on that, yet. Scientists have years of research ahead of them already, just to understand the inner-workings of TDP.
Some believe tardigrades may have “alien" DNA. To find out more, click here:
Join Radiolab's Latif Nasser at 1pm ET on Monday as he chats with Malcolm Gladwell live on Big Think.
University of Utah research finds that men are especially well suited for fisticuffs.
- With males having more upper-body mass than women, a study looks to find the reason.
- The study is based on the assumption that men have been fighters for so long that evolution has selected those best-equipped for the task.
- If men fought other men, winners would have survived and reproduced, losers not so much.
Built for mayhem<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjY2NDIyMy9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxMzk4NTQ2OX0.my6nML12F3fEQu3H4G0BScdqgaMZkRQHxgyj-Cmjmzk/img.jpg?width=980" id="906fc" class="rm-shortcode" data-rm-shortcode-id="dd77af7a881631355ed8972437846394" data-rm-shortcode-name="rebelmouse-image" />
Image source: Ollyy/Shutterstock<p>The researchers are, of course, talking averages here, not stating a rule: There are plenty of accomplished female pugilists, as well as lots of males who have no idea how to throw a punch.</p><p>Even so, says co-author <a href="https://www.wofford.edu/academics/majors-and-programs/biology/faculty-and-staff" target="_blank">Jeremy Morris</a> says, "The general approach to understanding why sexual dimorphism evolves is to measure the actual differences in the muscles or the skeletons of males and females of a given species, and then look at the behaviors that might be driving those differences."</p><p>Carrier has been interested in the idea that millennia of male fighting has shaped certain structures in male bodies. Previous research has reinforced his hunch:</p> <ul> <li><a href="https://jeb.biologists.org/content/216/2/236" target="_blank">When a hand is formed into a fist, its structure is self-protective</a>.</li> <li><a href="https://unews.utah.edu/flat-footed-fighters/" target="_blank">Heels planted firmly on the ground augment upper-body power</a>.</li> <li><a href="https://www.ncbi.nlm.nih.gov/pubmed/24909544" target="_blank">A study examined facial bone structure as being especially well-suited for taking a punch</a>.</li> </ul> <p>(That last one is our favorite. Do you know the German word "<a href="https://www.urbandictionary.com/define.php?term=Backpfeifengesicht" target="_blank">backpfeifengesicht</a>?" It's an adjective describing "a face that badly needs a punching.")</p><p>"One of the predictions that comes out of those," asserts Carrier, "is if we are specialized for punching, you might expect males to be particularly strong in the muscles that are associated with throwing a punch."</p>
Testing the theory<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjY2NDIzMy9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYwNzMxMTE2MH0.UXJICMy57UPYUWskhK98alctOrPidJL9yxMkz3HDQrM/img.jpg?width=980" id="98718" class="rm-shortcode" data-rm-shortcode-id="b12287684ac3e740b70392e6433a6b8f" data-rm-shortcode-name="rebelmouse-image" />
Image source: Ollyy/Shutterstock<p>The researchers measured the punching — and spear-throwing — force of 20 men and 19 women. The assumption was that early humans were punchers <em>and</em> spear-throwers.</p><p>Prior to testing, each participant had filled out an activity questionnaire so that "we weren't getting couch potatoes, we were getting people that were very fit and active," says Morris.</p><p>For punching, participants operated a hand crank that required movement similar to throwing a haymaker. The purpose of the hand crank was to spare participants any damage that might be inflicted on their fists by throwing actual punches. Subjects were also measured pulling a line forward over their heads to assess their strength at throwing a spear.</p><p>Even though all of the participants, male and female, were routinely fit, the average power of males was assessed as being 162% greater than females. There were no gender differences in throwing strength recorded. Other untested, though presumably likely, hand-to-hand combat activities come to mind including tackling, clubbing, running, kicking, scratching, and biting.</p><p>Carrier's takeaway: "This is a dramatic example of sexual dimorphism that's consistent with males becoming more specialized for fighting, and males fighting in a particular way, which is throwing punches."</p>
Boys will be boys<p>It, er, strikes us as odd that, even in science fiction — hi-tech weaponry notwithstanding — the hero <em>is</em> going to wind up duking it out with some bad guy, or alien, in the climactic battle. What is it about men punching, anyway? Are they more sexually attractive? The study suggests so:</p><p style="margin-left: 20px;"><em>The results of this study add to a set of recently identified characters indicating that sexual selection on male aggressive performance has played a role in the evolution of the human musculoskeletal system and the evolution of sexual dimorphism in hominins.</em></p><p>It's tough to contribute to the gene pool after being killed in battle.</p><p>Also, while the authors aren't <em>quite</em> saying that males' historical fighting role is mandated by biology and not by social expectations, neither are they quite <em>not</em> saying it.</p><p>As Carrier explain to <a href="https://attheu.utah.edu/facultystaff/carrier-punch/" target="_blank">theU</a>: "Human nature is also characterized by avoiding violence and finding ways to be cooperative and work together, to have empathy, to care for each other, right? There are two sides to who we are as a species. If our goal is to minimize all forms of violence in the future, then understanding our tendencies and what our nature really is, is going to help."</p>
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Cool hand rebuke<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDQyMTIyNy9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0NjY1NTYyOH0.0MCPKN3If94mYCNf3mMNrnTvJXjXN_bKLhgk9203EXk/img.jpg?width=917&coordinates=0%2C0%2C0%2C0&height=453" id="1627b" class="rm-shortcode" data-rm-shortcode-id="6d76421ba1ea0de4b09956b97e80c384" data-rm-shortcode-name="rebelmouse-image" />
A chart showing prison population rates (per 100,000 people) in 2018. The United States has the highest rate of incarceration in the world.