Posts Tagged ‘tardigrade’

By Dan Taylor

It’s a tiny little animal, but it is virtually impossible to kill, and scientists think it may one day outlive us. It’s the tardigrade, also known as the water bear, and these minuscule animals may not look like much, but they’re a lot tougher than we fragile humans are, the University of Oxford said in a statement after publishing a new paper on the animal.

Tardigrades have been known to survive the toughest conditions possible, including extreme heat, temperatures just barely above absolute zero, and even the vacuum of space. They’re known as the toughest critter on the planet, and this new study claims that they may very well be the last survivors of Earth, still kicking even after all the other creatures on Earth – including us – have perished.

And the tardigrade has lived for a very long time, certainly longer than the million years or so we’ve been around. Scientists have found tardigrade specimens in sediments that are dated between 100 and 520 million years old, so they’ve been around since the dinosaurs.

The full statement from the university follows below.

The world’s most indestructible species, the tardigrade, an eight-legged micro-animal, also known as the water bear, will survive until the Sun dies, according to a new Oxford University collaboration.

The new study published in Scientific Reports, has shown that the tiny creatures, will survive the risk of extinction from all astrophysical catastrophes, and be around for at least 10 billion years – far longer than the human race.

Although much attention has been given to the cataclysmic impact that an astrophysical event would have on human life, very little has been published around what it would take to kill the tardigrade, and wipe out life on this planet.

The research implies that life on Earth in general, will extend as long as the Sun keeps shining. It also reveals that once life emerges, it is surprisingly resilient and difficult to destroy, opening the possibility of life on other planets.

Tardigrades are the toughest, most resilient form of life on earth, able to survive for up to 30 years without food or water, and endure temperature extremes of up to 150 degrees Celsius, the deep sea and even the frozen vacuum of space. The water-dwelling micro animal can live for up to 60 years, and grow to a maximum size of 0.5mm, best seen under a microscope. Researchers from the Universities of Oxford and Harvard, have found that these life forms will likely survive all astrophysical calamities, such as an asteroid, since they will never be strong enough to boil off the world’s oceans.

Three potential events were considered as part of their research, including; large asteroid impact, and exploding stars in the form of supernovae or gamma ray bursts.

Asteroids

There are only a dozen known asteroids and dwarf planets with enough mass to boil the oceans (2×10^18 kg), these include (Vesta 2×10^20 kg) and Pluto (10^22 kg), however none of these objects will intersect the Earth’s orbit and pose a threat to tardigrades.

Supernova

In order to boil the oceans an exploding star would need to be 0.14 light-years away. The closest star to the Sun is four light years away and the probability of a massive star exploding close enough to Earth to kill all forms of life on it, within the Sun’s lifetime, is negligible.

Gamma-Ray bursts

Gamma-ray bursts are brighter and rarer than supernovae. Much like supernovas, gamma-ray bursts are too far away from earth to be considered a viable threat. To be able to boil the world’s oceans the burst would need to be no more than 40 light-years away, and the likelihood of a burst occurring so close is again, minor.

Dr Rafael Alves Batista, Co-author and Post-Doctoral Research Associate in the Department of Physics at Oxford University, said: ‘Without our technology protecting us, humans are a very sensitive species. Subtle changes in our environment impact us dramatically. There are many more resilient species’ on earth. Life on this planet can continue long after humans are gone.

‘Tardigrades are as close to indestructible as it gets on Earth, but it is possible that there are other resilient species examples elsewhere in the universe. In this context there is a real case for looking for life on Mars and in other areas of the solar system in general. If Tardigrades are earth’s most resilient species, who knows what else is out there.’

Dr David Sloan, Co-author and Post-Doctoral Research Associate in the Department of Physics at Oxford University, said: ‘A lot of previous work has focused on ‘doomsday’ scenarios on Earth – astrophysical events like supernovae that could wipe out the human race. Our study instead considered the hardiest species – the tardigrade. As we are now entering a stage of astronomy where we have seen exoplanets and are hoping to soon perform spectroscopy, looking for signatures of life, we should try to see just how fragile this hardiest life is. To our surprise we found that although nearby supernovae or large asteroid impacts would be catastrophic for people, tardigrades could be unaffected. Therefore it seems that life, once it gets going, is hard to wipe out entirely. Huge numbers of species, or even entire genera may become extinct, but life as a whole will go on.’

In highlighting the resilience of life in general, the research broadens the scope of life beyond Earth, within and outside of this solar system. Professor Abraham Loeb, co-author and chair of the Astronomy department at Harvard University, said: ‘It is difficult to eliminate all forms of life from a habitable planet. The history of Mars indicates that it once had an atmosphere that could have supported life, albeit under extreme conditions. Organisms with similar tolerances to radiation and temperature as tardigrades could survive long-term below the surface in these conditions. The subsurface oceans that are believed to exist on Europa and Enceladus, would have conditions similar to the deep oceans of Earth where tardigrades are found, volcanic vents providing heat in an environment devoid of light. The discovery of extremophiles in such locations would be a significant step forward in bracketing the range of conditions for life to exist on planets around other stars.’

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After being locked in a deep freeze for more than 30 years, two microscopic creatures called tardigrades have been resuscitated, with one of the adults getting busy with reproduction “immediately” and “repeatedly,” scientists reported. Scientists were even able to revive a tardigrade egg after it spent the past three decades cooling its jets alongside the mature duo in a researcher’s freezer.

Their findings shattered the previous preservation and revival record for tardigrades and their eggs, which had been eight years for frozen tardigrades and nine years for dried eggs stored at room temperature.

Scientists retrieved the two microscopic Acutuncus antarcticus hitchhikers and one egg from a piece of frozen moss that had been collected in Antarctica in 1983. For years, the moss was kept frozen at minus 4 degrees Fahrenheit (minus 20 degrees Celsius.) During that time, the tardigrades maintained a state known as “cryptobiosis,” showing no visible signs of life and with their metabolic processes at a standstill. But after more than 30 years in this suspended state, they were brought back to life. Scientists rehydrated them and video-recorded the results, observing that after just one day, a revived tardigrade was tentatively stretching a pair of its stubby legs. Six days after rehydration, the tardigrade was moving its body, as though it were trying to lift itself, the researchers noted. After 13 days had passed, the animal was eating algae, its first meal in decades, And after 22 days, eggs were visible inside the tardigrade’s chubby body. It eventually laid 19 eggs. A. antarcticus reproduce through parthenogenesis, which means that their embryos grow and develop without fertilization, and in this instance, a total of 14 hatchlings emerged. The other tardigrade survived for just 20 days after rehydration, and died without reproducing. But the frozen egg hatched and produced a larva that went on to lay 15 eggs, of which seven hatched successfully.

Tardigrades, which also go by the endearing names “water bears” and “moss piglets,” measure about 0.02 inches (0.5 mm) long. They have eight limbs tipped with clawlike structures that propel their plump, segmented bodies through a variety of watery, algae-rich environments all over the world. But they have a hidden superpower — surviving adverse conditions such as extreme heat or cold that would kill just about any other form of life. Tardigrades were even sent into low-Earth orbit in 2007, where they weathered exposure to space’s vacuum, cosmic rays and solar ultraviolet radiation. Their secret lies in an ability to expel all the water in their cells and generate a protective coating, suspending them in a deathlike but still-living state that they can maintain until conditions improve. Other tiny creatures are known for similar long-term preservation capabilities. The researchers described prior studies that revived refrigerated adult and larval nematodes, microscopic worms, after as long as 39 years. But reviving a tardigrade after 30 years is unprecedented, and their ability to reproduce after a brief recovery period is a testament to their durability. It also raises questions about their preservation mechanisms, and how they and other organisms can survive a deep-freeze recover, and how they repair cellular and DNA damage when they’re restored to life, Megumu Tsujimto, the lead researcher at National Institute of Polar Research, said in a statement. Looks like the cold never bothered them anyway. The study was published online Feb. 16 in the journal Cryobiology

See more at: http://www.livescience.com/53781-tardigrade-revived-after-30-years.html#sthash.cF8xM2Fn.dpuf