When a worm wriggles back to life after 46,000 freezing years in Siberia

Batagaika crater

A view of the Batagaika crater, as permafrost thaws causing a megaslump in the eroding landscape, in Russia’s Sakha Republic. (REUTERS)

Researchers found that specific organisms, like moss and tiny animals, can undergo a state of suspended animation called cryptobiosis. These worm wriggles can be revived even after extended periods.

Scientists have long been acquainted with a phenomenon known as “cryptobiosis,” where organisms significantly lower their metabolic rates, entering a state resembling deep slumber. This adjustment serves as a survival tactic against severe weather conditions that pose a potential threat. While I’m not suggesting these organisms possess hope, the potential implication is that they could potentially revive or be reanimated when conditions become more conducive.

In 2014, a group of scientists explored moss in Antarctica (“Millennial timescale regeneration in a moss from Antarctica,” Esme Roads et al, Current Biology, 17 March 2014). Their observations revealed that mosses “possess well-developed stress tolerance features enabling cryptobiosis.” Up until that point, the longest observed period of cryptobiosis was 20 years. However, these scientists discovered “small moss clumps” that had been encased in ice on Antarctica for 400 years. Remarkably, they successfully regenerated the moss.

A few years later, on the opposite side of the globe, a team of scientists retrieved “bdelloid rotifers” – not a distant relative of Rottweiler dogs, but microscopic multicellular animals – from Siberian soil samples that had endured freezing temperatures for approximately 24,000 years (“A living bdelloid rotifer from 24,000-year-old Arctic permafrost,” Lyubov Shmakova et al, Current Biology, 7 June 2021). The scientists noted that this marked “the longest reported case of rotifer survival in a frozen state.” Remarkably, they not only survived but also successfully recovered “numerous living rotifers.”

Subsequently, they exposed these microscopic creatures to conditions akin to what their more contemporary counterparts might face during their lifetimes: freezing and attempts at revival. The results revealed that there was no substantial difference in the freeze-tolerance between ancient species and their present-day counterparts. In essence, it wasn’t just that the rotifers frozen for 24,000 years could be revived; it was also that, unlike Eugeni, they could lead fairly normal lives in the present era.

Yet, you might ponder, what about animals of a slightly larger scale? How about, for instance, worms?

I’m glad you inquired. Just last month, a group of scientists released a paper detailing a species of nematode, a roundworm, initially gathered from Siberian permafrost in 2002 (“A novel nematode species from the Siberian permafrost shares adaptive mechanisms for cryptobiotic survival with C. elegans dauer larva,” Anastasia Shatilovich et al, PLOS Genetics, 27 July 2023, https://rb.gy/nlyf9).

Although nematodes aren’t microscopic, they measure only about a millimeter in length, making them still quite tiny. They’re ubiquitous, found in various environments worldwide—soil, rivers, the ocean floor, and beyond. One specific nematode species, Caenorhabditis elegans, is frequently employed in laboratory experiments globally. This provided the scientists with a familiar animal for comparison with the Siberian specimens.

Initially, they revealed a startling finding from the radio-carbon dating of the Siberian nematodes: these individuals have been in cryptobiosis since the late Pleistocene, approximately 46,000 years. This led to what a Scientific American report termed “by far the most stunning examples of … cryptobiosis – an organism’s ability to suspend its own metabolism in poor conditions.”

While dating back to the Pleistocene Age is fascinating, the crucial question remains: can this suspended metabolism be reawakened?

Exactly what these researchers aimed to unravel. Initially, they thawed the soil sample meticulously over several weeks to prevent inadvertently subjecting the nematodes to lethal temperatures. Eventually, they observed “motile nematodes,” indicating that the worms were engaging in typical worm behavior—wriggling about. They began consuming the bacteria thoughtfully provided by the scientists as their food source.

The story continues. The scientists christened this nematode Panagrolaimus kolymaensis, paying homage to the Kolyma River in Russia, the source of the collected samples. In several aspects, it wasn’t entirely unique. Similarities to C. elegans were discovered, hinting that many nematodes may have the potential to “suspend life over geological time scales.”

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Moreover, certain chosen P. kolymaensis females initiated the production of offspring through a process known as “parthenogenesis,” bypassing the need for males. Consider the implications: “otherwise extinct lineages” of certain species could potentially be rejuvenated if an individual in cryptobiosis for tens of thousands of years is identified. The scientists found this aspect “particularly interesting … as each individual can establish a new population [by] avoiding the cost of sex.”

Indeed, locating such an individual might allow it to “evade the cost of sex.” I wonder if it could or would ever forgive you. It’s a question I wish we could have posed to Eugeni.