Bdelloid rotifers are multicellular animals so small that you need a microscope to see them. Despite their size, they are known for their tenacity and can survive in dry, frozen, hungry, and low-oxygen environments. The paper, published June 7, 2021, in the journal Current Biology, shows that not only can they withstand the ice, but they can survive at least 24,000 years in Siberia’s permafrost.
The researchers say the paper is the strongest evidence yet that multicellular animals can withstand tens of thousands of years of freezing, a state in which metabolism almost stops completely. The researchers specifically isolated microbiota from the ancient permafrost of Siberia. To collect samples, they use drilling rigs in some of the most remote Arctic regions.
They have previously identified many single-celled microorganisms. There is also a report on nematodes from 30,000 years ago. Moss and some plants were also reborn after being trapped in ice for thousands of years. Now, the team has added aromatase to a list of creatures with extraordinary abilities that appear to be able to survive indefinitely in suspension beneath the frozen surface.
A close up of a bdelloid rotifer
According to early evidence, rotifers can survive up to 10 years in freezing. In the new study, researchers used radiocarbon dating to determine that the rotifers they found in permafrost were about 24,000 years old. Once thawed, the rotifers can reproduce in a clone called lone female reproduction. To track the freezing and recovery of ancient rotifers, researchers froze dozens of rotifers in the lab and then thawed them.
Studies have shown that rotifers can resist the formation of crystals during slow freezing. This suggests that they have mechanisms to protect their cells and organs from harm at ultra-low temperatures. The researchers say their harvest is that a multicellular organism can be frozen and stored for thousands of years in this way before returning to life. Of course, the more complex the organism, the trickier it is to freeze and save, which is currently impossible for mammals. However, from a single-celled organism to an organism with a gut and brain that can withstand freezing and survive, it is microscopic, but a great step forward.
The researchers say they will continue to explore Arctic samples to find other organisms that can withstand this long-term freeze. Ultimately, they want to learn more about the biological mechanisms that make rotifers live. Hopefully, the revelations from these tiny animals will provide clues as to how to better preserve the cells, tissues, and organs of other animals, including humans.