Bdelloid rotifers are multicellular animals so small that you need a microscope to see them. Despite their size, they are known to be tough, able to survive drying, freezing, starvation and lack of oxygen. Now researchers reporting in the journal Current biology on June 7 found that not only can they withstand frost, but they can also persist for at least 24,000 years in Siberian permafrost and survive.
“Our report is the strongest evidence to date that multicellular animals could withstand tens of thousands of years in cryptobiosis, the almost completely arrested state of metabolism,” says Stas Malavin of the Soil Cryology Lab Institute of physico-chemical and biological soil problems. Science in Pushchino, Russia.
The Soil Cryology Laboratory specializes in the isolation of microscopic organisms from ancient Siberian permafrost. To take samples, they use a drilling rig in some of the most remote places in the Arctic.
They have already identified many single-celled microbes. A 30,000 year old nematode worm has also been reported. Mosses and some plants have also been regenerated after thousands of years trapped in ice. Now the team is adding rotifers to the list of organisms with a remarkable ability to survive, seemingly indefinitely, in a state of animation suspended beneath the frozen landscape.
Rotifers have been reported to survive for up to 10 years when frozen, based on previous evidence. In the new study, the researchers used radiocarbon dating to determine that the rotifers they recovered from permafrost were around 24,000 years old.
Once thawed, the rotifer, which belongs to the genus Adineta, was able to reproduce in a clonal process called parthenogenesis. To follow the process of freezing and recovering the old rotifer, researchers frozen and then thawed dozens of rotifers in the laboratory.
Studies have shown that rotifers can resist the formation of ice crystals that occurs during slow freezing. This suggests that they have a mechanism to protect their cells and organs from damage at extremely low temperatures.
“The bottom line is that a multicellular organism can be frozen and stored as such for thousands of years and then come back to life – a dream of many fictional writers,” says Malavin. “Of course, the more complex the organism, the more delicate it is to keep it alive frozen and, for mammals, this is not currently possible. However, to go from a single-celled organism to an organism with a gut and a brain, although microscopic, is a big step forward. “
It’s not yet clear what it takes to survive on the ice for even a few years and if jumping to the thousands makes a big difference, he says. This is a question that requires further study. The researchers say they will continue to explore samples from the Arctic for other organisms capable of such long-term cryptobiosis.
Ultimately, they want to know more about the biological mechanisms that allow rotifers to survive. The hope is that the information from these tiny animals will offer clues as to how best to cryopreserve the cells, tissues and organs of other animals, including humans.
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