Roughly 24,000 years ago, a collective of microscopic creatures was frozen helplessly into a deep layer of Siberian permafrost, and experienced slowed biological activity, called suspended animation. But now they're waking up.
Scientists are reviving the microbial critters called bdelloid rotifers after an unconscionably long hibernation, according to a new study published in the journal Current Biology.
And, they are reproducing.
Frozen permafrost is ideal for preserving frozen extremophiles
In nature, some organisms are preserved in suspended animation for hundreds to tens of thousands of years. Antarctic moss stems more than one thousand years old were successfully regrown from a sample covered in ice for roughly 400 years. Entire companion plants were likewise regrown from seed tissue recovered from 32,000-year-old permafrost. Nematodes were brought back to life from source sediments that date back more than 30,000 years. But the microscopic and multicellular Bdelloid rotifers are renowned in scientific circles for their unique ability to withstand unbelievably low temperatures.
It's not a stretch to say this discovery "constitutes the longest reported case of rotifer survival in a frozen state", easily qualifying as something "of great interest not only for evolutionary biology but also for practical purposes of cryobiology and biotechnology," wrote the scientists in the Monday study. Rotifers are found throughout the world in freshwater, and scientists at the Soil Cryology Laboratory at the Institute of Physicochemical and Biological Problems in Soil Science in Russia decided to test the resilience of these creatures by gathering ice cores from a site close to the Alazeya River in northeastern Siberia.
"The cores were extracted from a site around 50 meters from the river bank," said Stas Malavin, co-author of the study who is also a researcher a the Soil Cryology Laboratory, in a report from VICE. "The depth at which the core used for isolation was extracted is well above the river water level, as those relic permafrost sediments, called 'yedoma', actually form permanently frozen hummocks that the river cuts through." Malavin and his colleagues were the ones who brought back nematodes from a 30,000-year frozen slumber, so they knew from experience that extremophiles can survive in suspended animation for tens of thousands of years.
Revived rotifers reproduced, creating their first offspring in 24,000 years
"Bdelloid rotifers are known for their ability to enter cryptobiosis in response to different adverse events like drying or freezing of the environment (and also starvation and low oxygen content)," added Malavin in the VICE report. "In fact, together with tardigrades, the 'water bears', they are among the toughest animals on the planet known to date. Thus, considering also the previous finding of nematodes, we were expecting to once find a bdelloid rotifer in our samples." The core sample, which was assessed via radiocarbon dating, was frozen roughly 24,000 years ago.
In other words, when mammoths still shuffled across the Siberian landscape. Microbes can't move up or down through ice or ice-covered ground, read the study, and this means the very old critters are the same age as the permafrost from which they were recovered. The sample contained dozens of samples, all from the genus Adineta, whose descendants still live to this day. Surprisingly, as soon as the tiny animals were thawed back into normal and active parameters, several of them reproduced asexually in a process called parthenogenesis. A new generation of the tiny rotifers came into being from parents 24,000 years their senior.
Nature is wild, but the ability of extremophiles like the rotifers could form part of the very early foundations of a science for a distant future where, like the characters in countless sci-fi novels, series, and films, humans may gain the ability to enter cryogenic suspended animation, and travel to the distant stars, survive an apocalypse, or travel to the future, without aging a single day. It's a long way from becoming a real technological capability, speaking on the basis of empirical science, but the possibilities are vast.