Frozen in Siberian Permafrost for 24,000 Years, Microscopic Animal Comes Back to Life

https://gizmodo.com/frozen-in-siberian-permafrost-for-24-000-years-microsc-1847045211

George DvorskyToday 11:00AM331Alerts

The revived rotifer.

A lone rotifer has awakened after spending the past 24,000 years in frozen hibernation. Scientists hope that further studies of this multicellular animal may lead to better ways of cryopreserving human cells, tissues, and organs.

Rotifers are worm-like aquatic animals that prefer freshwater environments and moist soil. These complex organisms aren’t as charismatic as tardigrades, another microscopic animal, but they’re likewise known for their extreme survival skills, as they’re capable of withstanding dehydration, freezing temperatures, starvation, and low oxygen levels. By reviving a 24,000-year-old rotifer found in Siberian permafrost, scientists have demonstrated that these creatures are even tougher than previously thought. The new findings were published today in Current Biology.

“Our report is the hardest proof as of today that multicellular animals could withstand tens of thousands of years in cryptobiosis, the state of almost completely arrested metabolism,” said Stas Malavin, a co-author of the study, in a press release. Malavin is a biologist at the Soil Cryology Laboratory at the Institute of Physicochemical and Biological Problems in Soil Science in Pushchino, Russia.

READ MORE

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Close-up view of the revived rotifer.

An impressive feat for a microbe, but a record it is probably not. Back in 2018, Russian scientists claimed to have resurrected nematode worms pulled from permafrost deposits dated to at least 32,000 years ago. Previous rotifer recovery records range from between six and 10 years, involving specimens found in Antarctic soil and on a glacier. The tardigrade record is 30 years, but given their track record, I have a sneaking suspicion they can withstand even longer durations of frozen hibernation.

https://imasdk.googleapis.com/js/core/bridge3.463.0_en.html#goog_1979616451https://imasdk.googleapis.com/js/core/bridge3.463.0_en.html#goog_1354533527https://imasdk.googleapis.com/js/core/bridge3.463.0_en.html#goog_336124331javascript:false

Credit for the new discovery goes to Russia’s Soil Cryobiology Lab, which uses drills to dig samples from Siberian permafrost. The resurrected rotifer was found near the Alazeya River in northeastern Siberia at a depth of 11.5 feet (3.5 meters). The team used special extraction methods to prevent contamination with neighboring layers, while also ruling out natural seepage from the layers above. The Late Pleistocene layer holding the rotifer specimen was radiocarbon-dated to approximately 24,000 years ago, which is roughly 12,500 years prior to the end of the most recent ice age.The revived rotifer during feeding.Gif: Lyubov Shmakova/Gizmodo

Back in the lab, the scientists managed to revive the rotifer and even produce several secondary rotifer cultures from the same individual (rotifers reproduce asexually in a process known as parthenogenesis). The reported revival “constitutes the longest reported case of rotifer survival in a frozen state,” according to the paper. Genetic analysis of the specimen identified it as belonging to the genus Adineta, and it compared rather nicely to living samples sourced from Belgium.

To learn more about rotifers and how they’re able to pull off this trick, the team randomly selected 144 unrelated rotifer specimens and kept them frozen at 5 degrees Fahrenheit (-15 degrees C) for one week. This experiment, though limited in scope, showed that the ancient Adineta specimen “was not significantly more freeze tolerant than contemporary species,” as the scientists wrote in their paper.

Setup of the subsequent freezing experiment.

“The takeaway is that a multicellular organism can be frozen and stored as such for thousands of years and then return back to life—a dream of many fiction writers,” said Malavin. “Of course, the more complex the organism, the trickier it is to preserve it alive frozen and, for mammals, it’s not currently possible. Yet, moving from a single-celled organism to an organism with a gut and brain, though microscopic, is a big step forward.”

Somehow, Adineta rotifers are able to fight the formation of ice crystals—the mortal enemy of the freezing process. Ice crystals are like tiny knives, and they destroy the integrity of cells and organs. Rotifers likely have some sort of “biochemical mechanisms of organ and cell shielding necessary to survive low temperatures,” according to the paper. A better understanding of this rotifer defense mechanism could go a long way in improving cryopreservation techniques to store cells, organs, and tissues at cold temperatures.

More speculatively, these insights could even advance the nascent field of cryonics, in which deceased humans are stored at liquid nitrogen temperatures. The revival of these frozen people may never happen, but the resilient rotifers are, at the very least, giving us hope.

MoreFrozen tardigrade brought back to life after 30 years.

Massive Flare Seen on Closest Star to the Solar System: What It Means for Chances of Alien Neighbors

TOPICS:AstrobiologyAstronomyAstrophysicsThe Conversation

By R. O. PARKE LOYD, ARIZONA STATE UNIVERSITY MAY 9, 2021

Proxima Centauri is the closest star to the solar system and is home to a potentially habitable planet. Credit: Hubble, European Space Agency

The Sun isn’t the only star to produce stellar flares. On April 21, 2021, a team of astronomers published new research describing the brightest flare ever measured from Proxima Centauri in ultraviolet light. To learn about this extraordinary event – and what it might mean for any life on the planets orbiting Earth’s closest neighboring star – The Conversation spoke with Parke Loyd, an astrophysicist at Arizona State University and co-author of the paper. Excerpts from our conversation are below and have been edited for length and clarity.

Why were you looking at Proxima Centauri?

Proxima Centauri is the closest star to this solar system. A couple of years ago, a team discovered that there is a planet – called Proxima b – orbiting the star. It’s just a little bit bigger than Earth, it’s probably rocky and it is in what is called the habitable zone, or the Goldilocks zone. This means that Proxima b is about the right distance from the star so that it could have liquid water on its surface.

But this star system differs from the Sun in a pretty key way. Proxima Centauri is a small star called a red dwarf – it’s around 15% of the radius of our Sun, and it’s substantially cooler. So Proxima b, in order for it to be in that Goldilocks zone, actually is a lot closer to Proxima Centauri than Earth is to the Sun.

You might think that a smaller star would be a tamer star, but that’s actually not the case at all – red dwarfs produce stellar flares a lot more frequently than the Sun does. So Proxima b, the closest planet in another solar system with a chance for having life, is subject to space weather that is a lot more violent than the space weather in Earth’s solar system.

Solar flares – like this one captured by a NASA satellite orbiting the Sun – eject huge amounts of radiation. Credit: NASA

What did you find?

In 2018, my colleague Meredith MacGregor discovered flashes of light coming from Proxima Centauri that looked very different from solar flares. She was using a telescope that detects light at millimeter wavelengths to monitor Proxima Centauri and saw a big of flash of light in this wavelength. Astronomers had never seen a stellar flare in millimeter wavelengths of light.

My colleagues and I wanted to learn more about these unusual brightenings in the millimeter light coming from the star and see whether they were actually flares or some other phenomenon. We used nine telescopes on Earth, as well as a satellite observatory, to get the longest set of observations – about two days’ worth – of Proxima Centauri with the most wavelength coverage that had ever been obtained.

Immediately we discovered a really strong flare. The ultraviolet light of the star increased by over 10,000 times in just a fraction of a second. If humans could see ultraviolet light, it would be like being blinded by the flash of a camera. Proxima Centauri got bright really fast. This increase lasted for only a couple of seconds, and then there was a gradual decline.

This discovery confirmed that indeed, these weird millimeter emissions are flares.

Proxima b – shown here in an artist’s rendering – is rocky and might support water or even life if the atmosphere is still intact. Credit: European Southern Observatory, M. Kornmesser

What does that mean for chances of life on the planet?

Astronomers are actively exploring this question at the moment because it can kind of go in either direction. When you hear ultraviolet radiation, you’re probably thinking about the fact that people wear sunscreen to try to protect ourselves from ultraviolet radiation here on Earth. Ultraviolet radiation can damage proteins and DNA in human cells, and this results in sunburns and can cause cancer. That would potentially be true for life on another planet as well.

On the flip side, messing with the chemistry of biological molecules can have its advantages – it could help spark life on another planet. Even though it might be a more challenging environment for life to sustain itself, it might be a better environment for life to be generated to begin with.

But the thing that astronomers and astrobiologists are most concerned about is that every time one of these huge flares occurs, it basically erodes away a bit of the atmosphere of any planets orbiting that star – including this potentially Earth-like planet. And if you don’t have an atmosphere left on your planet, then you definitely have a pretty hostile environment to life – there would be huge amounts of radiation, massive temperature fluctuations and little or no air to breathe. It’s not that life would be impossible, but having the surface of a planet basically directly exposed to space would be an environment totally different than anything on Earth.

Is there any atmosphere left on Proxima b?

That’s anybody’s guess at the moment. The fact that these flares are happening doesn’t bode well for that atmosphere being intact – especially if they’re associated with explosions of plasma like what happens on the Sun. But that’s why we’re doing this work. We hope the folks who build models of planetary atmospheres can take what our team has learned about these flares and try to figure out the odds for an atmosphere being sustained on this planet.

Written by R. O. Parke Loyd, Post-Doctoral Researcher in Astrophysics, Arizona State University.

Originally published on The Conversation.

Worlds With Underground Oceans – Like Europa, Titan, and Enceladus – May Be More Conducive to Supporting Life Than Earth

TOPICS:AstrobiologyAstronomyAstrophysicsEnceladusMoonsPopularSaturnSouthwest Research Institute

By SOUTHWEST RESEARCH INSTITUTE MARCH 20, 2021

Interior water ocean worlds like Saturn’s moon, Enceladus, are prevalent throughout the universe. New research from Southwest Research Institute suggests that layers of rock and ice may shield life within such oceans, protecting it from impacts, radiation and other hazards and concealing it from detection. Layers of rock and ice may therefore shield and protect life residing in them, and also sequester them from threats and detection. Credit: NASA/JPL-Caltech/Southwest Research Institute

Layers of ice and rock obviate the need for “habitable zone” and shield life against threats.

SwRI researcher theorizes worlds with underground oceans may be more conducive to life than worlds with surface oceans like Earth.

One of the most profound discoveries in planetary science over the past 25 years is that worlds with oceans beneath layers of rock and ice are common in our solar system. Such worlds include the icy satellites of the giant planets, like Europa, Titan, and Enceladus, and distant planets like Pluto.

In a report presented at the 52nd annual Lunar and Planetary Science Conference (LPSC 52) this week, Southwest Research Institute planetary scientist S. Alan Stern writes that the prevalence of interior water ocean worlds (IWOWs) in our solar system suggests they may be prevalent in other star systems as well, vastly expanding the conditions for planetary habitability and biological survival over time.

It has been known for many years that worlds like Earth, with oceans that lie on their surface, must reside within a narrow range of distances from their stars to maintain the temperatures that preserve those oceans. However, IWOWs are found over a much wider range of distances from their stars. This greatly expands the number of habitable worlds likely to exist across the galaxy.

Worlds like Earth, with oceans on their exterior, are also subject to many kinds of threats to life, ranging from asteroid and comet impacts, to stellar flares with dangerous radiation, to nearby supernova explosions and more. Stern’s paper points out that IWOWs are impervious to such threats because their oceans are protected by a roof of ice and rock, typically several to many tens of kilometers thick, that overlie their oceans.

“Interior water ocean worlds are better suited to provide many kinds of environmental stability, and are less likely to suffer threats to life from their own atmosphere, their star, their solar system, and the galaxy, than are worlds like Earth, which have their oceans on the outside,” said Stern.

He also points out that the same layer of rock and ice that protects the oceans on IWOWs also conceals life from being detected by virtually all astronomical techniques. If such worlds are the predominant abodes of life in the galaxy and if intelligent life arises in them — both big “ifs,” Stern emphasizes — then IWOWs may also help crack the so-called Fermi Paradox. Posed by Nobel Laureate Enrico Fermi in the early 1960s, the Fermi Paradox questions why we don’t see obvious evidence of life if it’s prevalent across the universe.

“The same protective layer of ice and rock that creates stable environments for life also sequesters that life from easy detection,” said Stern.

In 2015, NASA created the Ocean Worlds Exploration Program, which seeks to explore an ocean world to determine habitability and seek life. Moons that harbor oceans under a shell of ice, such as Europa and Titan, are already the targets of NASA missions to study the habitability of these worlds.

The paper, “Some Implications for Both Life and Civilizations Regarding Interior Water Ocean Worlds” at LPSC 52 is available here (PDF).

Meeting: 52nd annual Lunar and Planetary Science Conference (LPSC 52)

Scientists accidentally found life under 3,000 feet of ice in Antarctica. ‘Never in a million years’ would they have expected it, the lead scientist said.

Marianne Guenot 9 hours ago

https://www.businessinsider.com/scientist-discover-life-3000-ft-under-ice-in-antarctica-2021-2

Animals found under Ice
An image from a video in which scientists saw stationary animals under ice in Antarctica. The creatures appear similar to sponges. 
  • Scientists stumbled upon life under 3,000 feet of ice in Antarctica.
  • They found two types of unidentified animals, where they had thought nothing could live.
  • Their next step is finding a way to get close enough to identify the creatures.
  • Visit the Business section of Insider for more stories.

Scientist have found life under 3,000 feet under of ice in Antarctica, challenging their assumption that nothing could live in such conditions.

The previous theory was that life couldn’t exist in such extremity: no food, freezing temperatures, and complete darkness.

The creatures were found attached to a boulder in the frigid seas under the Filchner-Ronne ice shelf. Experts from the British Antarctic Survey drilled through 2,860 feet of ice and then another 1,549 feet of water before making the discovery.

“The area underneath these ice shelves is probably one of the least-known habitats on Earth,” said Huw Griffiths, one of the scientists who made the discovery, in a Twitter video.https://f33ab413356d2368bc962a909775bc69.safeframe.googlesyndication.com/safeframe/1-0-37/html/container.html

“We didn’t think that these kinds of animals, like sponges, would be found there.”https://platform.twitter.com/embed/Tweet.html?dnt=false&embedId=twitter-widget-0&frame=false&hideCard=false&hideThread=false&id=1361198202905636864&lang=en&origin=https%3A%2F%2Fwww.businessinsider.com%2Fscientist-discover-life-3000-ft-under-ice-in-antarctica-2021-2&siteScreenName=SciInsider&theme=light&widgetsVersion=889aa01%3A1612811843556&width=550px

The Filchner-Ronne ice shelf is a massive floating ice sheet that stretches out from Antarctica.

It spans more than 579,000 square miles, but little has been explored under the ice.

Enormous icebergs occasionally break off ice shelves and drift away. In December, one of these icebergs threatened to crash into a breeding ground for sealions and penguins.

Filchner Ronne Ice Shelf, Antartica
An annotated satellite image of the Filchner-Ronne ice shelf. 
ice sheets
The Filchner-Ronne ice shelf is the second-biggest ice shelf in Antarctica. 

The scientists didn’t set out looking for life.https://f33ab413356d2368bc962a909775bc69.safeframe.googlesyndication.com/safeframe/1-0-37/html/container.html

They were drilling through the ice sheet to collect samples from the sea floor. Instead, their camera hit a boulder. When they reviewed the camera’s footage, it revealed this discovery.https://platform.twitter.com/embed/Tweet.html?dnt=false&embedId=twitter-widget-1&frame=false&hideCard=false&hideThread=true&id=1361198202905636864&lang=en&origin=https%3A%2F%2Fwww.businessinsider.com%2Fscientist-discover-life-3000-ft-under-ice-in-antarctica-2021-2&siteScreenName=SciInsider&theme=light&widgetsVersion=889aa01%3A1612811843556&width=550px

“Never in a million years would we have thought about looking for this kind of life, because we didn’t think it would be there,” Griffiths told The Guardian.

The video reveals two types of unidentified animals, shown here in a video from the British Antarctic Survey. The animals in red seem to have long stalks, whereas another type of animal, highlighted in white, looks more like a round sponge-like animal.

annotated video footage, new discovery animals, Antarctica
An annotated image of the footage that captured animals under the ice in Antarctica. 

Other studies had looked at life under ice sheets. A few mobile animals, such as fish, worms, jellyfish, or krill, could be found in that habitat.https://f33ab413356d2368bc962a909775bc69.safeframe.googlesyndication.com/safeframe/1-0-37/html/container.html

But it was thought that the deeper and farther away from a light source the habitat stretched, the less likely that life could be found.

He may have found the key to the origins of life. So why have so few heard of him?

Hungarian biologist Tibor Gánti is an obscure figure. Now, more than a decade after his death, his ideas about how life began are finally coming to fruition.

An oil painting of Hungarian biologist Tibor Gánti.PAINTING BY LÁSZLÓ GULYÁS7 MINUTE READBY MICHAEL MARSHALL

https://www.nationalgeographic.com/science/2020/12/he-may-have-found-the-key-to-origins-of-life-tibor-ganti-chemoton/


https://70043c440e1e866f32d3f4922aa073a4.safeframe.googlesyndication.com/safeframe/1-0-37/html/container.html

PUBLISHED DECEMBER 14, 2020

WHEN BIOLOGIST TIBOR Gánti died on April 15, 2009, at the age of 75, he was far from a household name. Much of his career had been spent behind the Iron Curtain that divided Europe for decades, hindering an exchange of ideas.

But if Gánti’s theories had been more widely known during the communist era, he might now be acclaimed as one of the most innovative biologists of the 20th century. That’s because he devised a model of the simplest possible living organism, which he called the chemoton, that points to an exciting explanation for how life on Earth began.

The origin of life is one of science’s most perplexing mysteries, partly because it is several mysteries in one. What was Earth like when it formed? What gases made up the air? Of the thousands of chemicals that living cells now use, which ones are essential—and when did those must-have substances arise?

Perhaps the hardest question is the simplest: What was the first organism?

For scientists attempting to re-create the spark of life, the chemoton offers an attractive target for experiments. If non-living chemicals can be made to self-assemble into a chemoton, that reveals a pathway by which life could have formed from scratch. Even now, some research groups are edging startlingly close to this model.

And for astrobiologists interested in life beyond our planet, the chemoton offers a universal definition of life, one not tied to specific chemicals like DNA, but instead to an overall organizational model.

“I think Gánti has thought deeper about the fundamentals of life than anybody else I know,” says biologist Eörs Szathmáry of the Centre for Ecological Research in Tihany, Hungary.

Life’s beginning

There is no agreed scientific definition of life, though not for want of trying: A 2012 paper identified 123 published definitions. It’s challenging to write one that encompasses all life but that excludes everything non-living with life-like attributes, such as fire and cars. Many definitions say that living things can reproduce. But a rabbit, or a human, or a whale on its own cannot reproduce.

In 1994 a NASA committee described life as “a self-sustaining chemical system capable of Darwinian evolution.” The word “system” can mean an individual organism, a population, or an ecosystem. That gets around the reeproduction problem, but at a cost: vagueness.https://70043c440e1e866f32d3f4922aa073a4.safeframe.googlesyndication.com/safeframe/1-0-37/html/container.html

How a chemoton works

A theoretical model for the simplest form of life requires three interlocking mechanisms:

a metabolic cycle, for turning food into energy; template replication, for reproduction;

and a membrane, to delineate the organism.

Food molecules are

absorbed from the environment and picked up by the metabolic cycle.

The replicator produces a chemical that is a key component of the membrane.

1

4

Template

Replication

The metabolic cycle uses the molecules to make parts for the replicator.

3

Metabolic

Cycle

The metabolic

cycle makes parts for the membrane.

The waste products

of the metabolic cycle

are released outside

of the membrane.

2

5

CHRISTOPHER TURNER

SOURCE: LEONARDO BICH AND SARA GREEN, SYNTHESE, APRIL 2017

What few people knew at the time was that Gánti had offered another way two decades earlier.

Tibor Gánti was born in 1933 in the small town of Vác, in central Hungary. His early life was colored by conflict. Hungary allied itself with Nazi Germany in World War II, but in 1945 its army was defeated by the Soviet Union. The totalitarian regime would dominate eastern Eurasia for decades, with Hungary becoming a satellite state, like most other eastern European countries.

Fascinated by the nature of living things, Gánti studied chemical engineering before becoming an industrial biochemist. In 1966 he published a book on molecular biology called Forradalom az Élet Kutatásában, or Revolution in Life Research, a dominant university textbook for years—partly because few others were available. The book asked whether science understood how life was organized, and concluded that it did not.

In 1971 Gánti tackled the problem head-on in a new book, Az Élet Princípiuma, or The Principles of Life. Published only in Hungarian, this book contained the first version of his chemoton model, which described what he saw as the fundamental unit of life. However, this early model of the organism was incomplete, and it would take him another three years to publish what is now regarded as the definitive versionagain only in Hungarian, in a paper that is not available online.

Miracle year

Globally, 1971 was something of a banner year for research into the origin of life. In addition to Gánti’s underdog work, science put forward two other important theoretical models.

The first came from American theoretical biologist Stuart Kauffman, who argued that living organisms must be able to copy themselves. In speculating about how this might have worked before cells formed, he focused on mixtures of chemicals.

Suppose, he argued, that chemical A drives the formation of chemical B, which then drives the formation of chemical C, and so on, until something in the chain makes a fresh version of chemical A. After one cycle, two copies of each set of chemicals will exist. Given sufficient raw materials, another cycle will yield four copies, and continue exponentially.https://70043c440e1e866f32d3f4922aa073a4.safeframe.googlesyndication.com/safeframe/1-0-37/html/container.html

Kauffman called such a group an “autocatalytic set,” and he argued that such groups of chemicals could have been the foundation for the first life, with the sets becoming more intricate until they produced and used a range of complex molecules, such as DNA.

In the second idea, German chemist Manfred Eigen described what he called a “hypercycle,” in which several autocatalytic sets combine to form a single larger one. Eigen’s variant introduces a crucial distinction: In a hypercycle, some of the chemicals are genes and are therefore made of DNA or some other nucleic acid, while others are proteins that are made-to-order based on the information in the genes. This system could evolve based on changes—mutations—in the genes, a function that Kauffman’s model lacked.

Gánti had independently arrived at a similar notion, but he pushed it even further. He argued that two key processes must take place in every living organism. First, it has to build and maintain its body; that is, it needs a metabolism. Second, it has to have some sort of information storage system, such as a gene or genes, that could be copied and passed on to offspring.

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SpaceX’s Starship First High-Altitude Flight

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Gánti’s first version of this model was essentially two autocatalytic sets with distinct functions that combined to form a larger autocatalytic set—not so different from Eigen’s hypercycle. However, the following year Gánti was questioned by a journalist who pointed out a key flaw. Gánti assumed the two systems were based on chemicals floating in water. But left to themselves, they would drift apart, and the chemoton would “die.”

The only solution was to add a third system: an outer barrier to contain them. In living cells, this barrier is a membrane made of fat-like chemicals called lipids. The chemoton had to have such a barrier to hold itself together, and Gánti concluded that it also had to be autocatalytic so that it could maintain itself and grow.

Here at last was the full chemoton, Gánti’s concept of the simplest possible living organism: genes, metabolism, and membrane, all linked. The metabolism produces building blocks for the genes and membrane, and the genes exert an influence over the membrane. Together they form a self-replicating unit: a cell so simple it could not only arise with relative ease on Earth, it could even account for alternate biochemistries on alien worlds.

More: https://www.nationalgeographic.com/science/2020/12/he-may-have-found-the-key-to-origins-of-life-tibor-ganti-chemoton/

Are Tardigrades The Most Indestructible Animals on Earth? There’s a Close Contender

(Steve Gschmeissner/Science Photo Library/Getty Images)

NATURE

EVA HAMRUD, METAFACT

https://www.sciencealert.com/are-tardigrades-the-most-indestructible-animals-on-earth-there-s-a-close-contender

5 SEPTEMBER 2020

Humans wouldn’t survive two minutes in space, but in 2007, two species of tardigrades were released into space and then collected again – still alive.

Tardigrades are a group of tiny invertebrate species that live all over the world – you can probably find one yourself on a piece of moss in your back garden or local park. Actually, you can find them pretty much anywhere – on a mountain top, at the bottom of the sea or even in a volcano!

Astrobiologist Dr Jon Stone from McMaster University summarises how they can survive a battery of extreme conditions, including temperatures as cold as -180°C for 14 days or oven heat of 151°C for 30 minutes.

They can also survive “5000 Gy gamma radiation (which is the radiation type that, in the Marvel Universe, transformed David Banner into the Incredible Hulk). Where 5-10 Gy kills humans” says Dr Stone.

They can also survive being in a frozen state for 30 years and potentially up to 100 years, although that long is still contested writes Dr Stone.

But are tardigrades the most indestructible animals on Earth? We asked eight biologists who study them – 63 percent said “Yes” meaning there is still some debate on this question. Here’s what we learned from experts.

Why are tardigrades so indestructible?

When conditions are difficult to live in, tardigrades curl up into a ball called a tun. When in a tun, the tardigrade goes into a kind of ‘paused’ state, called ‘cryptobiosis’.

During cryptobiosis, animals don’t move, grow or reproduce, but they are protected from extreme conditions. There are multiple types of cryptobiosis depending on what conditions you are dealing with.

The best-studied type is called ‘anhydrobiosis’, which protects from cells drying out when there is no water.

If cells dry out, lots of things can get damaged like their DNA and membranes. When some animals undergo anhydrobiosis, their cells become filled with a sugar called trehalose, which protects the cell contents until there is water again.

Anhydrobiosis in tardigrades was discovered way back in 1702, when scientist Anton von Leewenhoek dried out and revived the tardigrades he found on house roofs. Tardigrades can remain in cryptobiosis with no food or water for years, for at least 30 years if frozen.

Marine tardigrades are not indestructible

There are more than 1,400 known species of tardigrades and each differs in their ability to undergo different types of cryptobiosis. Biologist Dr William Miller From Baker University explains, “Terrestrial tardigrades in cryptobiosis are very resistant to destruction … But marine and freshwater tardigrades do not exhibit cryptobiosis, and thus are very destructible.”

Similarly, only some species of tardigrades make trehalose, the sugar substance that protects cells during anhydrobiosis.

The species of tardigrades that don’t make trehalose may have some other tricks to protect them from harsh conditions like special proteins that turn into a glass-like substance to protect cells. There is lots of interesting research to be done to understand this set of survival tools, but it’s clear tardigrades can’t all be lumped together.

Some things that can destroy a tardigrade

Generally tardigrades are way more resistant to changes in their environment than most animals. They are often studied in an astrophysical context – for example identifying whether they would survive if Earth was hit by an asteroid.

However, this doesn’t mean they are indestructible against everything – as expert Dr Dennis Persson puts it, “Tardigrades are certainly one of the most stress-tolerant animals on Earth, but they are very easily destroyed with the prick of a needle, or eaten by other animals, fungi and protists.”

Although tardigrades are resilient in some ways, they are vulnerable to things that most animals are in danger of, such as predators and infections.

Tardigrades vs Nematodes

Working out whether tardigrades are the most indestructible animals, we need to know about the competition. Ecologist Dr Diego Fontaneto explains that ‘other animals can survive what we consider extreme conditions for life.

Among them, there are nematodes and rotifers, which share similar life-history strategies, habitats, and body size with tardigrades. These animals survive desiccation and freezing as much as tardigrades, if not even better than tardigrades.’

Other animals that have the cryptobiosis trick up their sleeves include nematode worms, some kinds of shrimp, and even some species of plants and yeast! Nematodes have been particularly well studied, and paleobiologist Dr Graham Budd notes that “The record for survival in a dehydrated state is held by the nematode Tylenchus polyhypnus at 39 years.”

And the tardigrade Vs nematode battle has not been verified yet. “In general, as different animals have different survival capabilities in different conditions, it is difficult to single one type out as the ‘most resilient ever’,” says Dr Budd.

Takeaway: Tardigrades may be the most indestructible animal, but they are not resistant to any type of harm and many experts say Nematodes are a close challenger to this title. Despite the debate, it’s certain that we are only just beginning to learn which creatures can cope in extreme environments, and how they do it.

Article based on 8 expert answers to this question: Are tardigrades the most indestructible animal on Earth?

This expert response was published in partnership with independent fact-checking platform Metafact.io. Subscribe to their weekly newsletter here.