Tag Archives: Tardigrade

Rare tardigrade fossil discovered in 16-million-year-old amber

Tardigrades, microscopic animals that live in water and are really good at coping with extreme environments and surviving decades without food. But for all their resilience, they’re rarely fossilized. Now, in a new study, researchers have found a 16-million-year-old-fossil in an ancient piece of amber from the Dominican Republic. 

Image credit: The researchers.

Only two fossils of the creature were ever found before, although tardigrades have been around for over 90 million years. This last discovery is the first tardigrade fossil to be recovered from the current Cenozoic era, which started 66 million years ago. The researchers believe it’s the best-imaged fossil tardigrade to date. 

The tardigrade earned its own genus and name, Paradoryphoribius chronocaribbeus, because it’s so different from previously known specimens. It’s part of the modern tardigrade family Isohypsibioidea and it will help to better understand the evolutionary history of tardigrades, which are creatures of particular interest for researchers. 

“The discovery of a fossil tardigrade is truly a once-in-a-generation event,” Phil Barden, senior author of the study, said in a statement. “What is so remarkable is that tardigrades are a ubiquitous ancient lineage that has seen it all on Earth, from the fall of the dinosaurs to the rise of terrestrial colonization of plants. Yet, they are like a ghost lineage.”

The tardigrade was actually spotted by Barden’s co-author Brendon Boudinot, who saw it next to the ants that he had been analyzing in the ancient amber. At first he thought it was a crack or fissure that happened to look like a tardigrade. While extremely happy, he considered the discovery was “enough tardigrade luck for one career.”

The remarkable tardigrades

The researchers used a high-powered laser confocal fluorescence microscopy to look further at the fossil and its place on the tardigrade ancestral tree. This allowed to look at the specimen in very close detail. Then they compared it across morphological features associated with most of the tardigrade groups alive today, such as body surface and egg morphology. 

“The fact that we had to rely on imaging techniques usually reserved for cellular and molecular biology shows how challenging it is to study fossil tardigrades,” Javier Ortega-Hernandez, co-author, said in a statement. “We hope that this work encourages colleagues to look more closely at their amber samples with similar techniques to better understand these cryptic organisms”.

The discovery is only “scratching the surface” of our understanding of the tardigrades, the researchers said, hoping further findings could come in the future. The fact that this specimen was found in an amber deposit suggests that others could have been overlooked in the past. Finding more fossils would allow us to learn more about how tardigrades have changed over time. 

Around 400 species of tardigrades that have been discovered so far, and they seem to be able to survive in all sort of environments. From freshwater mosses to the deep ocean, these creatures can survive up to 30 years without food, temperatures going from absolute zero to above boiling and including in the vacuum of space. They are trully remarkable and worth studying further. 

For now, it’s all excitement among the group of researchers, who even wrote a song to commemorate the occasion. It goes like this: “Tardigrade amber fossils, there were only two. …Well now, there’s three. Now that you know there’s three, there’s another mystery. What could this fossil be? Well, look at our paper and you’ll see.”

The study was published in the journal Proceedings of the Royal Society B. 

In this microscope image, the tardigrade resembles a vacuum cleaner sac rather than a water bear. Still cute, though.

Tardigrades can survive being shot from a gun. What this means for alien life

Microscope image of a tardigrade (Paramacrobiotus craterlaki) in moss. 

Despite their adorable appearance and microscopic size, tardigrades are some of the toughest creatures in the animal kingdom. They can survive without water for 10 years, in extreme pressures and temperatures, deadly UV radiation, and even in outer space. Even after they were frozen for 30 years, some thawed tardigrades were still alive and could even reproduce.

Now, scientists have pushed the limits of these extremophiles by shooting them out of a high-speed gas gun into an impact target. Remarkably, many survived — but only up to a point.

Although the experiment might sound cynical and random, there’s more to it than just proving how tough tardigrades are. One of the biggest questions in science is how life first appeared on this planet. One of the wildest theories suggests that microbes hitched a ride to our planet on meteorites and comets.

This theory of interplanetary transfer of life, known as panspermia, has never been proven but it is plausible enough that scientists have spent a considerable amount of time and funding to investigate it. For instance, researchers at Harvard and MIT teamed up with NASA to design and produce an instrument that can be sent to Mars and potentially detect DNA or more primitive RNA.

The topic was recently brought to scientists’ attention after Israel’s Beresheet probe crash landed on the moon in 2019, along with a cargo of tardigrades. The probe was obliterated, but some couldn’t help but wonder if the sturdy water bears made it out alive despite the rain of destruction.

Researchers at the University of Kent in the UK saw this as a challenge. They designed an experiment that would mimic the high-speed impact of a spacecraft by shooting the water bears as projectiles from a two-stage light gas gun. These guns are used by researchers to test the effects of high-velocity impacts, such as the effects of space debris impacting a satellite. As such, they can fire projectiles at much higher velocities than a normal gun that shoots bullets.

Tardigrades usually live for only a few months when fully active. But when short on water, they may curl up in a ball, entering the so-called “tun” state, named because it looks like a large barrel called a tun. By freezing the water bears, the researchers were able to activate the tun state — they were now ready to be fired like tiny cannonballs.

Six shots were fired onto a sand target, each shot containing a few frozen water bears with speeds ranging from 1,240 to 2,230 miles per hour. The water bears impacted the target at shock pressures between 0.61 and 1.31 GPa (gigapascals).

The tardigrades remarkably survived some of these impacts, up to velocities of 1,845 miles per hour (900 meters/second) and 1.14 GPa of pressure upon impact. More than that killed the tiny creatures. But even those that survived seem to have sustained internal damage since they took longer to thaw and recover than their counterparts that just sat in the lab’s freezer. It’s not yet clear if these battered tardigrades can reproduce.

If the Beresheet probe crashed into the moon at more than 1,845 miles per hour, then there are likely no more water bears left there. Likewise, most meteorites impact Earth at much higher velocities and shock pressures than measured by this experiment.

However, panspermia isn’t entirely down for the count. The researchers claim that up to 40% of the rock and debris that were shot into space by asteroid impacts in Earth’s early history billions of years ago would have reached the moon’s surface at speeds low enough for tardigrades to survive. Likewise, a similar journey could have been made between Mars and its moon Phobos.

Rather than debunking panspermia, these new findings serve to offer a potential upper bound for the kind of impacts life may survive. They could also prove useful in missions to Saturn’s Enceladus or Jupiter’s Europa, both icy moons that bear subsurface oceans. Although these oceans are obscured by ice dozens of miles thick, material from deep beneath the ice is ejected into space by huge plumes of water. A spacecraft flying through these sprinklers would have to collect samples at a speed much slower than the impact survival limit of tardigrades to ensure that any organisms, if any, survive the process.

The findings appeared in the journal Astrobiology.

How the water bear defies death even in the vacuum of space by wrapping its cells in glass

Tardigrades are the toughest, most resilient animals we know of. They can survive temperatures from 1 K (−458 °F; −272 °C) to about 420 K (300 °F; 150 °C), pressures six times greater than those found in the deepest ocean trenches, ionizing radiation at doses hundreds of times higher than the lethal dose for a human, and the vacuum of outer space. One tardigrade female was brought back to life after being frozen for 30 years then birthed 14 healthy babies. 

Water bear don’t care

Simply put, the tardigrade, also known as the water bear, is the most extreme survivalist out there. If there’s an animal that knows how to make it against all odds, it’s this guy and, as you might imagine, a lot of people are interested to find out what its secret weapons are.

The water bear is able to withstand such extreme conditions by going into a sort of safe mode, as it dries up into a little barrel called a tun. In this form, neither heat, cold or the wretched vacuum of space can kill it. Essentially, the tiny bear which is smaller than 1 millimeter enters a state called anhydrobiosis during which the metabolism shuts down.

Now, researchers from the University of North Carolina at Chapel Hill have found another ace up the water bear’s sleeve. During a dry spell when water is scarce anti-dehydrating proteins called tardigrade-specific intrinsically disordered proteins (TDPs) become vitrified. When this happens all the tardigrade’s dehydration-sensitive tissue and cells become protected by a glass surface. This way, sensitive proteins and other biological molecules are locked in place. They can’t fold, they can’t break apart nor can they aggregate together, which explains how the animal can survive in space and then come back to life like nothing happened within an hour.

The video below shows how much the water bear shrinks when deprived of water.

https://www.youtube.com/watch?v=09U9tc-aaek

The team led by Thomas Boothby intentionally subjected the tardigrades to conditions that would force them to dry out. Meanwhile, they carefully monitored the animal’s gene activity. Boothby and colleagues noticed a spike of activity in a group of genes when the TDPs were produced. When such genes were blocked through genetic engineering, the tardigrade died of dehydration.

When bacteria and yeast were artificially infused with the aforementioned genes, these became much more resilient in the face of dehydration. This remarkable experiment suggests that, at least partly, the tardigrade’s tricks can be passed down to creatures. For instance, one interesting idea would be to produce new genetically modified crops that carry TDP genes to help them survive droughts. California’s worst drought in history, which is still not over and sure as heck isn’t the last, serves as a reminder that such crops are badly needed.

Previously, a 2008 study concluded that the tardigrade’s anhydrobiosis is linked to specialized sugars called trehalose. Tree frogs use the same sugar molecules to come with dry environments as well but not everyone was convinced the water bear uses the same mechanism because the study could only find trehalose-linked processes in only one species of tardigrade. Indeed, Boothby found tardigrades either don’t make or make very little amounts of trehalose.

It’s amazing however that TDPs work much in the same way as trehalose — they both protect cells by forming literally glass structures. So, what we’re essentially dealing with is yet another textbook example of convergent evolution — two animals (tardigrade and tree frog) totally unrelated from each other who evolved the same adaptive trait.

Another water bear trick involves using other proteins to shield its DNA against radiation. A previous research found  17.5 percent of a tardigrade’s genome was comprised of foreign DNA, including genes from bacterial species that can withstand extreme pressure and heat.

Next, the researchers plan on investigating other animals and even plant seeds which seem to survive desiccation to see whether they use the same proteins. Besides drought-resistant crops, such investigations might one day lead to amazing practical applications. One immediate application could be a new medium for storing vaccines and pharmaceuticals at room temperature by using dehydration instead of refrigeration. A much farther away application might involve dehydrating people to induce a hibernation-like state, which could be useful in interstellar flight.

tardigrade gif

Journal ref: T.C. Boothby et al., “Tardigrades use intrinsically disordered proteins to survive desiccation,” Molecular Cell, doi:10.1016/j.molcel.2017.02.018, 2017.

Computer generated tardigrade. Credit: Fox

Water bears, the amazing animals that can survive in outer space, have a unique adaptation that shields DNA from radiation

Computer generated tardigrade. Credit: Fox

Computer generated tardigrade. Credit: Fox

Tardigrades or water bears, as they’re often adorably called, are some of the most amazing animals out there. Considered the most extreme animal on the planet, the water bear can withstand intense heat, cold, pressure, radiation, even the vacuum of space. There’s a lot we could learn from it and a recent genome sequencing of the animal’s DNA might explain why it’s so freaking indestructible.

The animal that can withstand outer space and can come back from the dead

In 2007, researchers attached thousands of the 1mm-long tardigrades to a satellite and blasted them into space. Weeks later, after the satellite returned back to Earth, researchers found many of them had survived and, remarkably, some females even laid eggs — in space. The newly hatched younglings were healthy.

Tardigrades, who first appeared some 500 million years ago during the Cambrian, can even come back from the dead, as Japanese cryobiologists recently demonstrated. The Japanese researchers thawed some water bears that had been frozen for 30 years and found some of the defrosted creatures were still alive. What’s more, they could even manage to reproduce with one laying 19 eggs of which 14 successfully hatched.

To pull off these death-defying feats, tardigrades employ a couple of tricks. When faced with the prospect of annihilation, either due to lack of food or due to exposure to absolute zero temperatures, the water bear essentially dries out and retracts its head and its eight legs. It then enters a deep state of suspended animation that closely resembles death. Its metabolism slows to 0.01% of the normal rate and the body becomes almost devoid of water.  The video below shows how much the water bear shrinks when deprived of water.

https://www.youtube.com/watch?time_continue=6&v=09U9tc-aaek

This suspended state can be maintained for decades, as the Japanese researchers proved earlier, and the water bear can be revived when placed in contact with water.

The thing is, this process damages the DNA yet the extremophiles don’t seem to mind at all. In fact, they seem to flourish in spite of this.

Previously, researchers at University of North Carolina (UNC) at Chapel Hill sequenced a tardigrade’s genome and found 17.5 percent of it was comprised of foreign DNA. This means that some of its genes come from entirely different species. Most species, including humans, don’t have more than one percent foreign DNA in their genomes, so tardigrades have more foreign DNA than any other species. The previous record-holder was a microscopic animal known as a rotifer.

“Animals that can survive extreme stresses may be particularly prone to acquiring foreign genes — and bacterial genes might be better able to withstand stresses than animal ones,” Thomas Boothby, first author of the study said.

The UNC researchers found tardigrades had 6,000 foreign genes, mainly from bacteria. There are many bacterial species that can withstand extreme pressure and heat, which might explain the tardigrades’ resilience. Yet the study didn’t answer how the water bears cope with having their DNA damaged to the point of obliteration.

A new study published in the journal Nature Communications this week might be revealing in this respect. University of Tokyo researchers sequenced the genome of a water bear (Ramazzottius variornatus) and found the small aquatic animal has a gene coding a single protein which confers resistance to DNA damage in human cultured cells.

The protein is unique to the tardigrades and helps cells tolerate DNA damage. Besides this mysterious protein, the team led by Takekazu Kuieda found other genes responsible for the tolerance of stressful environments.

It’s still unclear how the tardigrades’ unique adaptations function at the molecular level, but evidence is piling up that these tiny critters evolved unique strategies to cope with stressful conditions. Until we know for sure what makes the water bear such an extreme hero, here’s a cute video of one such creature walking on moss.

A frozen tardigrad was brought back to life – and then gave birth

We’ve written about tardigrades before – the microscopic water bears that defy all odds and are quite possibly the toughest multi-cellular microorganisms out there. Now, they’ve broken the record for something which shouldn’t even have a record to be broken (if that makes any sense) – a tardigrade has been brought to life after being frozen solid for 30 years. Soon after that, it gave birth to 14 healthy babies.

Credit: Megumu Tsujimotoa et. al.

Tardigrades are waterborne micro-animals also called water bears or moss piglets. Their name literally means “slow stepper.” They can survive anywhere from mountaintops to the deep sea, from tropical rain forests to the Antarctic. They can withstand temperatures from 1 K (−458 °F; −272 °C) to about 420 K (300 °F; 150 °C), pressures six times greater than those found in the deepest ocean trenches, ionizing radiation at doses hundreds of times higher than the lethal dose for a human, and the vacuum of outer space.

Still not impressed?

They can survive without food for more than 10 years, and as has already been shown a couple of times, they can freeze solid, then thaw and come back to life. Researchers in Japan brought back such a tardigrade frozen in 1983, and not only did a healthy baby hatch from it six days later, but it went on to produce offspring shortly after.

Being frozen caused the tardigrades and eggs to undergo a process known as cryptobiosis. Cryptobiosis is a state in which the body shuts down virtually all metabolic functions. An organism in a perfect cryptobiotic state can essentially live indefinitely until environmental conditions return to being hospitable. Of course, there are no perfect states, but the tardigrades got pretty damn close to it.

“We recorded recovery of two individuals and development of a separate egg of the Antarctic tardigrade, Acutuncus antarcticus, providing the longest records of survival for tardigrades as animals or eggs,” the researchers report.

The researchers have reported their findings in the journal Cryobiology:

“SB-1 first showed slight movement in its fourth pair of legs on the first day after re-hydration. This progressed to twisting of the body from day 5 along with movement in its first and second pairs of legs, but the movements remained slow.

After starting to attempt to lift itself on day 6, SB-1 started to slowly crawl on the agar surface of the culture well on day 9, and started to eat the algal food provided… in the culture plate on day 13.”

Now, researchers are following closely to see how their metabolic processes return to life one after one.

Largest genetic complement identified, owned by the water bear

Also known as the water bear, the tardigrade has a lot to be proud of — this tiny organism is nigh-indestructible, known to have survived in extreme temperatures ( -272C to +151C / -457.6F to 303.8F) and to be the only animal that can brave the vacuum of space unprotected and live to tell the tale. A team from the University of North Carolina at Chapel Hill, curious as to how the tardigrade can accomplish such incredible feats, sequenced the genome of the microorganism. Their paper, published in the journal PNAS, reveals that a huge chunk of its DNA is of foreign origin — nearly 17.5% of the water bear’s genome (some 6000 genes) are primarily of bacterial origin, though genes from fungi and plants have also been identified.

Looks fluffy.
Image via wikimedia

Defined as the shifting of genetic material materially between organisms, horizontal gene transfer is widespread in the microscopic world. The process occurs in humans too but in a limited fashion, and via transposons and viruses. Microscopic animals however are known to have large complements of foreign genes.

Until today, the rotifer held the title for ” the greatest complement of foreign DNA of any microscopic organism,” but the newly-sequenced tardigrade genome includes twice as many genes as those boasted by the rotifer. And the authors have a theory as to why this extremely extensive gene transfer may have occurred.

Tardigrades have long been known to undergo and survive the process of desiccation (extreme drying out). The authors believe that this process is extremely harsh on the tardigrade’s genome, with strands of DNA suffering significant sheering and breakage, causing a general loss of integrity and leakiness of the water bear’s nucleus. This may allow foreign genetic material to easily exploit such gaps in the genome and integrate themselves, similar to the gene-transfer procedure known as electroportation.

For now, the tardigrade has a dual claim to fame, being the only known animal to survive the vacuum of space, and being the animal with the largest genetic complement.

Not bad for a 1.5mm long bug.