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A female microscopic roundworm that had been dormant for 46,000 years in the Siberian tundra was brought back to life and began reproducing in a lab dish.
In a report that was published on Thursday in the journal PLOS Genetics, researchers detailed the new species of nematode they discovered by decoding the genome of this Rip Van Winkle roundworm. Nematodes are among the most pervasive creatures on Earth today, living in the soil, water, and ocean floor.
The University of Florida's William Crow, a nematologist who was not involved in the study, stated in an email that "the vast majority of nematode species have not been described." He suggested that the ancient Siberian worm may have been a species that is now extinct. The possibility exists, though, that it might be a common nematode that hasn't been properly described.
The study's lead author, Philipp Schiffer, group leader at the Institute for Zoology at the University of Cologne, said that aside from the "wow" factor of a time-traveling nematode, there is a practical reason to investigate how these tiny, spindle-shaped organisms hibernate to survive in harsh environments. As ecosystems change as a result of rising global temperatures and shifting weather patterns, such research may shed additional light on how, at the molecular level, animals can adapt.
In an email, Schiffer stated, "We need to know how animals adapted to the extreme via evolution to maybe help species surviving now and people as well.
A revived prehistoric nematode
The ability of some microscopic organisms to halt their metabolism to undetectable levels and enter the deepest kind of sleep in order to live in hostile conditions has long been known to scientists. This process is known as cryptobiosis.
East of Russia's Lake Baikal, under the permafrost, a living several thousand-year-old crab was found in 1936. After 24,000 years under the Siberian permafrost, scientists revealed in 2021 that they had revived ancient bdelloid rotifers, tiny multicellular organisms.
The previous nematode resuscitation record was set by an Antarctic species that began squirming about again after only a few dozen years.
That record for dormancy is shattered by tens of thousands of years by this new nematode species, Panagrolaimus kolymaensis. The nematode was found trapped in frozen dirt that had been dug out of a long-ago gopher tunnel that was 130 feet underground. The dirt was 46,000 years old, give or take a thousand years, as determined by scientists using radiocarbon dating.
"One of the shocking things is how long it survived," said Gregory Copenhaver, co-editor of PLOS Genetics and head of the Institute for Convergent Science at the University of North Carolina at Chapel Hill. He emphasised that the last 46,000 years extend into the previous geologic epoch known as the Pleistocene, and that "this single organism, the actual individual they found, has been alive over that period of time."
The molecular underpinnings of suspended animation
According to Schiffer, the method for resurrecting these organisms is rather straightforward. The dirt is thawed slowly to avoid frying the worms. The worms then begin squirming and multiplying, devouring bacteria in a lab dish.
The original 46,000-year-old nematode is no longer alive, but scientists have raised over 100 generations from it. Parthenogenesis is the process through which a species reproduces without a partner.
The researchers are intrigued not only by the specimen's age, but also by how it enters a condition of limbo.
They discovered that the new nematode species, like another small roundworm, C. elegans, survives freezing and drying out better if it is subjected to moderately desiccating circumstances prior to the deep freeze. During this preconditioning, the worms begin pumping out trehalose, a sugar that may be important in protecting their DNA, cells, and proteins from degradation.
Teymuras Kurzchalia, emeritus professor at the Max Planck Institute for Molecular Cell Biology and Genetics, said that attempts are underway to determine which proteins are required for the process, utilising techniques that can mute or knock off genes.
"We still have much to learn about the mechanisms of desiccation tolerance," Kurzchalia added.
Researchers are also interested in whether there is a limit to how long an organism may survive and be revived, as well as what it implies for evolution and even the concept of extinction if organisms that normally live, breed, and die in weeks might live for years or millennia.
The 46,000-year-old nematode species has a normal life span of one to two months.
"They are alive because they move, eat bacteria on the culture plates, and reproduce," Schiffer explained.
Teymuras Kurzchalia, emeritus professor at the Max Planck Institute for Molecular Cell Biology and Genetics, said that attempts are underway to determine which proteins are required for the process, utilising techniques that can mute or knock off genes.
"We still have much to learn about the mechanisms of desiccation tolerance," Kurzchalia added.
Researchers are also interested in whether there is a limit to how long an organism may survive and be revived, as well as what it implies for evolution and even the concept of extinction if organisms that normally live, breed, and die in weeks might live for years or millennia.
The 46,000-year-old nematode species has a normal life span of one to two months.
"They are alive because they move, eat bacteria on the culture plates, and reproduce," Schiffer explained.