Rotifers survive being frozen for 24,000 years

Resurrected and hardier than a tardigrade, rotifers are the new bad boy from the (ice) block.

A new paper, published in Current Biology, described how microscopic animals, called Bdelloid rotifers, were thawed out after being in the ancient Siberian permafrost for 24,000 years – and they didn’t mind one bit.

Fast Facts: Rotifers

A close up of a worm-like creature. There is a lot of texture inside and out
Lateral view of a rotifer. Credit: Michael Plewka.
  • These microscopic animals have worm-like bodies.
  • With around 450 species, their fossil record spans 25 million years.
  • They live in freshwater all over the world but can survive when it is dry by becoming dormant.
  • Rotifers reproduce asexually – no sperm needed.
  • The tiny beasts are 150–700 micrometres long.

“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,” says Stas Malavin of the Institute of Physicochemical and Biological Problems in Soil Science in Pushchino, Russia, who led the study.

When frozen, organisms go into suspended animation: their metabolism and body functions completely stop. That’s not usually very healthy for an animal, so it’s extremely rare for multicellular organisms to survive.

Despite this, the newly resurrected rotifers, from the genus Adineta, got down to business and started reproducing themselves through a process called parthenogenesis – a form of asexual reproduction where no sperm is needed.

A rotifer recovering from being frozen for a week. Credit: Lyubov Shmakova.

The team froze and unfroze them to see what happened in those first stages of freezing, and found that they could withstand the formation of ice crystals from the permafrost. The authors suggest this may hint at some form of cellular shield that protects their organs.

“The takeaway is that a multicellular organism can be frozen and stored as such for thousands of years and then return back to life – a dream of many fiction writers,” Malavin says.

“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.”

For comparison, tardigrades, which are often touted as the great, resilient cryptobiosis survivors, lasted a mere 30 years.

The authors want to study more frozen Arctic beasties to learn the biological mechanisms behind surviving frozen for so long. They hope these insights will further knowledge about how to cryo-preserve other animal tissues, organs and maybe even humans.

A rotifer feeding. Credit: Lyubov Shmakova.

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