Image: Shatilovich et al, 2023, PLOS Genetics, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
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Scientists have revived tiny animals called nematodes from a slumber that lasted 46,000 years, reports a new study.
The microscopic animals were successfully woken from a state of suspended animation after researchers found them in the permafrost, or frozen soil, that flanks Siberia’s northern Kolyma River. A radiocarbon analysis revealed that they hail from a prehistoric era when Neanderthals and dire wolves still roamed the world, and that they belong to a functionally extinct species called Panagrolaimus kolymaensis that was previously unknown to science.
The astonishing discovery is “important for the understanding of evolutionary processes because 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,” according to a study published on Thursday in the journal PLoS Genetics.
“Their evolution was literally suspended for 40k years,” wrote Philipp Schiffer, an evolutionary biologist at the University of Cologne and a co-author of the study, in an email to Motherboard.
“We are now comparing them to species from the same genus, which my team samples around the world,” he continued, noting that he is currently conducting fieldwork in the Australian Outback. “Studying their genomes we hope to understand a lot about how these populations became different in the last 40k years.”
Nematodes, or roundworms, are a highly adaptable group of squiggly animals that are often microscopic, though some species are visible to the naked eye. Many nematodes have evolved the ability to survive freezing temperatures by entering a state of so-called “cryobiosis” in which they essentially shut down their metabolic systems and transform into desiccated husks that can be resuscitated once favorable conditions return.
Scientists have resurrected many organisms that existed in the deep past, including a bacterial species that lived at least 25 million years ago and left viable spores inside an amber fossil. Indeed, some of the authors of the new study previously revived nematodes found in the permafrost Russia’s Yakutia region that may have been 41,000 years old.
Now, Schiffer and his colleagues have extended the timeline back several millennia further with the discovery of P. kolymaensis in Siberian permafrost. The nematodes were found in permafrost formations along the Kolyma River that preserve the fossil burrows of arctic gophers that date back 45,839 to 47,769 years before the present day, according to the team’s radiocarbon analysis of ancient plant material in the samples.
Fortunately, the nematodes did not require much coaxing to start wiggling around and producing modern descendents, despite having dozed through the end of the last ice age and the subsequent rise of human civilization. The team has nurtured more than 100 generations of P. kolymaensis in the laboratory, with each new generation lasting about 8 to 12 days.
“Basically, you only have to bring the worms into amenable conditions, on a culture (agar) plate with some bacteria, some humidity and room temperature,” Schiffer explained. “They just start crawling around then. They also just start reproducing. In this case this is even easier, as it is an all-female (asexual) species. They don‘t need to find males and have sex, they just start making eggs, which develop.”
The idea that an animal could conk out for a geological era, only to wake up and start multiplying, sounds like something out of science fiction. But the new study suggests that nematodes, and perhaps other hardy species, have harnessed this superpower in order to ride out tough times. The findings open a window into the deep past while also raising questions about how organisms will adapt to future pressures, including those unleashed by humans.
“Cryptobiosis is on the interphase of life and death,” Schiffer concluded. “It allows species to survive very extreme conditions. Studying the process allows us to understand how species do this on a genetic and biochemical level. Naturally, with many habitats becoming extreme, we can learn a lot here about how species might evolve during global change.”