Roundworms are amazingly resistant
Researchers have now found that samples of so-called permafrost sediment contain nematodes, which started to move and eat again after thawing. The roundworms had been frozen for the past 40,000 years. This is a record for the longest time that an animal can survive a so-called cryogenic preservation.
In their current study, scientists at Moscow State University found that roundworms contained in permafrost are able to survive cryogenic preservation for over 40,000 years. The doctors published the results of their study in the English-language journal "Doklady Biological Sciences".
Worms started to live a few weeks after thawing
The roundworms contained in the permafrost began to move and eat within a few weeks of thawing. In addition to showing new limits to cryogenic preservation, the results could also be important when it comes to preserving our own tissues, the authors say.
More than 300 samples were examined
For their study, Russian biologists dug a total of more than 300 samples of frozen soil of different ages and locations and brought them back to their laboratory in Moscow to examine them more closely. Samples that were taken from remote areas of Northeast Russia contained nematodes from two different genera, which the researchers placed in petri dishes with a nutrient medium.
The oldest sample was about 42,000 years old
The worms were kept at 20 degrees Celsius for several weeks until they began to show signs of life. Some of the worms belonging to the Panagrolaimus genus were found 30 meters underground, in a former mound that collapsed some 32,000 years ago. Other specimens of the genus Plectus were found in a drill sample at a depth of only about 3.5 meters. The carbon dating was then used to determine the age of the sample, which was approximately 42,000 years, the scientists explain. Contamination of the samples cannot be ruled out, but the researchers claim that they have followed strict sterility procedures.
The animals were really frozen continuously
These worms are not known to dig deep into the permafrost and seasonal thawing is usually limited to around 80 centimeters. There was also no evidence of a possible thawing beyond a depth of 1.5 meters, when the area was warmer about 9,000 years ago, the doctors explain. This makes the scientists pretty sure that the worms have really been frozen for an incredibly long time.
With bacteria, reviving old organisms is nothing new
The revival of old organisms is in itself nothing new. In 2000, scientists pulled spores from Bacillus bacteria that were hidden in 250 million year old salt crystals. At that time, the specialists were able to bring these bacteria to life.
More research is needed
Such survivability is certainly impressive, but unfortunately we cannot apply the life-sustaining tricks of bacteria to our intricate tissues. Finding animals that can survive frozen for tens of thousands of years is a really interesting discovery that should be explored further, the study's authors say.
Results could drive cryopreservation
Roundworms are known to be robust creatures. Nematodes were resuscitated in 39-year-old herbarium specimens, but nothing of a similar magnitude has been observed to date. Close relatives of roundworms, so-called tardigrade, are also known to survive extreme conditions and repair damaged DNA. Even with these living things, a state of conservation has never been observed so long that enables survival after freezing. The current record of tardigrade is around 30 years. Finding out more about the biochemical mechanisms that nematodes use to limit the damage of ice and prevent the destruction of DNA over the millennia could lead the way to better cryopreservation technologies.
Adaptive mechanisms are very interesting for science
Other organisms that can convert their liquids to ice, such as wood frogs, have also been studied. Maybe someday human tissue could be frozen for transplants. Perhaps the whole body could even be frozen in order to be revived later, the experts speculate. The Pleistocene nematodes have some adaptive mechanisms that can be of scientific and practical importance for related areas of science such as cryomedicine, cryobiology and astrobiology, the scientists explain.
Can permafrost also release dangerous pathogens?
However, the current find also has a much darker side. There are fears that the melting of permafrost could release pathogens that have been frozen for tens of thousands of years. Nematodes are not particularly worrying, but their survival is evidence that a variety of organisms, from bacteria to animals and plants to fungi, may return after a long absence. What this means for the surrounding ecosystems has not yet been predicted, the researchers say. One can only hope that Siberia's melting ice will only release harmless worms and not any dangerous pathogens. (as)