Worms rise from dead after 46,000 years

Tiny nematodes are able to wriggle back to life after epochs in the Siberian permafrost.

The worm has stretched scientists’ definitions of what it means to be alive. Picture: The Times

When the worm went to sleep in the Siberian soil, the pyramids had not been built or the hanging gardens of Babylon sown, and our ancestors shared the planet with Neanderthals.

When the worm awoke, 46,000 years later, it found itself in a world where it would be transported in aircraft and have its genetic code stored on a computer, and where not only had the Neanderthals gone extinct, but so too, it appeared, had the worm’s own species.

No longer. The worm, which researchers called Panagrolaimus kolymaensis, has been resurrected after lying dormant in the permafrost.

Scientists have demonstrated that it is a species capable not merely of surviving in stasis but of doing so over geological time. Now we may have to rethink the evolutionary history of nematode worms.

Researchers write in the journal PloS Genetics: “Generation times could be stretched from days to millennia, and long-term survival of individuals of species can lead to the refoundation of otherwise extinct lineages.”

Teymuras Kurzchalia, a professor at the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden, Germany, said nematodes stretched our definition of what it was to be alive.

“They can exist in this world that is neither life nor death,” he said.

Kurzchalia was studying a related species, Caenorhabditis elegans, in 2018. He was fascinated by the theories of “cryptobiosis”, in which metabolism drops to a near-undetectable level.

There are scattered extreme examples of this in nature. Some seeds have been germinated after centuries, bacteria have been reanimated after millions of years and some Antarctic nematodes – a significantly more complex form of life than a bacterium – have survived frozen for decades.

Kurzchalia wanted to study this process methodically in the laboratory. He and his colleagues showed it was possible to induce the larvae of Caenorhabditis elegans to enter a dormant state, first through dessication, then freezing. They managed to reanimate one after 500 days.

“There was major excitement that life could be stopped,” he said. The skill has clear advantages.

If a larva were born at a time of drought or cold, it could wait until conditions were more favourable. Kurzchalia was thinking this might be beneficial on the scale of months to years, however, rather than epochs.

Then he heard about the discovery in the Siberian permafrost. Two frozen nematodes taken from deep underground had apparently been thawed.

Anastasia Shatilovich, a Russian scientist, was invited to Dresden to collaborate. She flew in with the worms in her pocket.

When their genome was sequenced, scientists realised it did not match any known species. Carbon dating of the soil the worms came from showed they had been in stasis since the late Pleistocene, when humans were moving from Africa into Europe. It is possible that whatever they evolved into still exists, but if so, it has not been detected.

Dr Philipp Schiffer, a co-author of the study from Cologne University, said it would be exciting if a descendant were found because it would have been evolving for 100,000 generations. He said he wanted to go to Siberia so “we could see what happened in terms of genome evolution in the last 46,000 years … totally fascinating”.

For now, the worms’ world is a German laboratory, where they exist as perhaps the only examples of their species. But Panagrolaimus kolymaensis has proved itself a survivor. Kurzchalia said: “Maybe these guys will live another 46,000 years.”

The Times