Several nematodes unearthed in the permafrost of northeastern Siberia are wriggling around and eating, just as normal nematodes do, in Petri dishes at the Russian Academy of Sciences. This is an astounding feat considering that the tiny organisms, also known as roundworms, had previously been frozen since the Pleistocene.
According to a team of researchers from Moscow and Princeton, one group of nematodes were found in a glacial core sample taken from 30 meters (almost 100 feet) below the surface of a permafrost deposit near the banks of the Kolyma River. Radiocarbon dating shows that the compacted soil and plant remains within the sample are 32,000 years old. A second group of worms was isolated from a 3.5-meter-deep (11.5-foot-deep) sample of a deposit near the Alazeya River, dated to 41,700 years – give or take 1,400 – before present.
Considering that the ground in this region only thaws to a depth of roughly 80 centimeters (2.6 feet) per year and hasn’t thawed to more than 1.5 meters (4.9 feet) in about 100,000 years, the scientists argue that there is no way the organisms discovered represent modern nematodes that infiltrated the tightly packed layers of permafrost.
“Thus, our data demonstrate the ability of multicellular organisms to survive long-term (tens of thousands of years) cryobiosis under the conditions of natural cryoconservation,” they wrote in the journal Doklady Biological Sciences. “It is obvious that this ability suggests that the Pleistocene nematodes have some adaptive mechanisms that may be of scientific and practical importance for the related fields of science, such as cryomedicine, cryobiology, and astrobiology.”
As the authors explain, previous investigations have shown that nematodes – a diverse animal phylum including more than 25,000 species – can withstand a variety of extreme conditions that would rapidly kill many other organisms. Researchers trying to determine how several species native to the Arctic and Antarctic can survive cycles of freezing and thawing discovered in the early 2000s that the worms turn to a cold climate adaptation, wherein they rapidly excrete the water in their cells as temperatures approach freezing.
This process – called cryoprotective dehydration – prevents the tissue destruction that occurs when water molecules inside cells expand during crystallization and rupture cell walls.
Laboratory experiments had also proved that nematodes can recover from frozen dormancy periods lasting up to 39 years. Yet until now, no one had ever isolated ancient specimens and revived them.
After removing the worms from the glacial samples, they were brought back to the Academy and placed in 20°C (68°F) culture with agar and E. coli bacteria as food.
“After being defrosted, the nematodes showed signs of life,” said a report from the area where the worms were found, according to the Siberian Times. “They started moving and eating.”
Subsequent examinations revealed that the Kolyma worms belong to the genus Panagrolaimus, whereas the Alazeya ones belong to Plectus – all are female.