Rotifers Found Still Alive in Siberian Ice After 24,000 Years

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An Arctic rotifer, looking pretty good for its age (24,000 years).
An Arctic rotifer, looking pretty good for its age (24,000 years).Credit: Michael Plewka

Life is starting to confuse us. One assumes that one is born and then one dies, and that cryo-preservation for possible resurrection some time in the future is the stuff of sci-fi. For you it is, at this point. But for the rotifer, a microscopic yet complex creature, that is life.

Bdelloid rotifers caught in the Siberian permafrost 24,000 years ago are still alive, Lyubov Shmakova, Stas Malavin and colleagues reported in the journal Current Biology on Monday.

“Our report is the hardest proof as of today that multicellular animals could withstand tens of thousands of years in cryptobiosis, the state of almost completely arrested metabolism,” stated Malavin of the Soil Cryology Laboratory at the Institute of Physicochemical and Biological Problems in Soil Science in Pushchino, Russia.

Rotifers are completely different from tardigrades, another wee animal that’s been teaching us how little we understand about life and survival. Israel famously, if accidentally, left tardigrades on the moon, but despite their extraordinary toughness, those individuals are expected to be dead because of the momentum of their crash on the lunar surface.

Not so these rotifers, which belong to the genus Adineta (and have relatives living in Belgium), and which were collected by the Soil Cryology Lab by drilling into the Siberian permafrost in the remote Arctic. The animals were extracted from a depth of 3.5 meters (about 11 feet) in the ice, which various indicators indicate had never thawed in all that time.

They’re far from the first ancient animal researchers have found in the ice and revived. The list includes microbes and even nematodes (primitive worms that last crawled in and crawled out 42,000 years ago). The wee’uns were all lady worms and they didn’t just twitch after being thawed – they ate, LiveScience reported in 2018.

Pools of water on the tundra in Russia's Western Siberia, once home to permafrost.Credit: AP

The rotifers went one better. After being awakened from their 30,000-year slumber, they ... it would be nice to write “had sex,” but if they did, it was with themselves. They did in any case engage in parthenogenesis, which means they reproduced asexually, producing clones.

All this was a tad surprising, perhaps; rotifers had been known to survive up to 10 years in ice, when kept at minus 20 to zero degrees Celsius (minus 4 degrees to 32 degrees Fahrenheit). The age of the rotifers thawed out of the permafrost was determined using radiocarbon dating of parallel organic material, at 24,000 years of age. The team notes that due to the nature of the ground, the rotifers were trapped in the permafrost at the same time as the organic material.

The team also noted that they performed experiments with the ancient rotifers and with modern ones to see how well they withstand (survive) being frozen and thawed. “The ancient Adineta sp. was more freeze resistant than its genetically closest relative,” they write.

OK. One problem with cryopreservation is that ice crystals forming as the cell freezes may burst membranes and cause other internal havoc. How the rotifers survived that remains unclear, but their experiments on subjecting the rotifers to ice regimens suggest that a gradual freezing process was key, the researchers say.

They note that some mosses and plants can also be resurrected after thousands of years trapped in the ice.

Over in the alternative universe of the Levant, other scientists resurrected a type of date palm that had existed in Israel in biblical times, but went extinct. They did it by managing to sprout seeds over 2,000 years old that were preserved in desert conditions.

A close-up of a rotifer.Credit: Michael Plewka

Clearly the cryopreservation of mammals is still a fantasy, but that of rotifers, a multicellular animal with a gut, is not. “Of course, the more complex the organism, the trickier it is to preserve it alive frozen and, for mammals, it’s not currently possible. Yet, moving from a single-celled organism to an organism with a gut and brain, though microscopic, is a big step forward,” Malavin explained.

He added that how they survive in ice for years, let alone thousands of years, isn’t clear – or if the length of time even makes a difference. Logic suggests that it does. Maybe one day we will be able to dunk a loved one in liquid nitrogen or some other cryo-fluid, for whatever reason, and meanwhile the team is looking for more ancient creatures in the permafrost. Which is melting in our era of climate change, and releasing not only pitiful baby mammothswoolly rhinoceroses and anthrax-riddled, long-dead reindeer, but ancient bacteria and viruses too. Stay tuned for more interesting, if not necessarily good, news.

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