A group of scientists from the Russian Institute of Physicochemical and Biological Problems in Soil Sciences (ISTC) thawed several worms that had been petrified for centuries. The incredible results were reported in the journal Current Biology.
The specialists found the rotifers in permafrost, a layer of permanently frozen soil, which functions as a very dry, almost oxygen-free, and very stable refrigerator over the millennia.
Bdeloid rotifers, microscopic multicellular animals similar to semi-translucent larvae, can live and reproduce after returning to room temperature having spent more than 40 000 years in a layer of frozen soil in Siberia.
What Happened to the Worms in Siberia?
By thawing these rotifers, the researchers were able to observe how the tiny multicellular animals moved, fed, and reproduced. In something never seen before, the worms were alive after having been at least 40,000 years in a state of dormancy, or near-complete suspension of their metabolic processes.
In previous studies, the worms had survived up to ten years when frozen at minus 20 degrees Celsius, but this is the longest case of survival of these creatures in freezing, according to Stas Malavin, a researcher at ISTC’s Soil Cryology Laboratory.
Obviously, these multicellular animals are so small that a microscope is needed to see them. Bdeloid rotifers are known to be very hardy and able to survive environmental dryness, starvation, lack of oxygen, and extremely cold temperatures. This is a spectacular example of this.
Where Were the Frozen Worms?
These rotifers were found in Siberia, a territory located in the eastern Asian part of Russia. Siberia is known to be one of the coldest regions on the planet and the worms were found under the famous layer of soil called ‘permafrost’ where the temperature has been below zero uninterruptedly for thousands of years, although it is not always covered with ice or snow.
The researchers found the bdelloid rotifers by drilling into the ice of an Arctic region northwest of Siberia at a depth of about 3.5 meters, reaching the ‘permafrost’ which, according to the researchers, functions as a large, very dry, anoxic (with an almost total lack of oxygen) and stable refrigerator.
When the time came to thaw these rotifers in the laboratory, they were able to observe how the tiny multicellular animals moved, fed, and reproduced, that is to say, that they were alive. No one could believe it.
In this new study, Russian scientists used radiocarbon dating techniques to determine that the rotifers they recovered from Siberian Arctic permafrost were several thousand times older than previously known scientifically.
The ISTC Soil Cryology Laboratory specializes in isolating microscopic organisms from ancient Siberian permafrost and uses a drilling platform in some of the most remote locations in the Arctic to collect its samples.
A Historic Discovery in Siberia
This study “is the strongest evidence to date that multicellular animals could spend tens of thousands of years in cryptobiosis, a state in which metabolism is almost completely halted,” as Stas Malavin explains.
This rotifer appears to be an extreme case of cryptobiosis, a state of dormancy or metabolic suspension into which some living things enter under adverse environmental conditions and during which chemical reactions in their cells are halted to obtain the nutrients and energy they need to grow, develop, reproduce and sustain life.
An organism can live in a cryptobiotic state until environmental conditions become suitable for its life again. According to the researchers, cases of cryptobiosis have previously been identified in unicellular microbes, and nematode worms extracted from the permafrost of northeastern Siberia have been revived in sediments more than 30,000 years old.
In permanently frozen natural habitats some organisms can be preserved for hundreds or tens of thousands of years. “Some mosses and plants have also regenerated after many thousands of years trapped in ice.”
Antarctic moss stems successfully regrown from a sample more than a millennium old that had been covered by ice for about 400 years, and entire camas plants have been regenerated from seeds preserved in permafrost about 32 000 years old.
“Now, the ISTC team has just added rotifers to the list of organisms with a remarkable ability to survive, seemingly indefinitely, in a state of suspended animation beneath the icy landscape,” Malavin said.
It Didn’t End There for the Siberian Worms
Once thawed, the worms, of the genus Adineta, were able to reproduce continuously in the laboratory by a process known as parthenogenesis, a mode of reproduction that involves the formation of a new being from the repeated division of unfertilized female sex cells, that is, cells that have not previously united with male gametes.
The studies showed that rotifers could resist the formation of ice crystals that occurs during slow freezing, suggesting that these multicellular beings have some mechanism to protect their cells and organs from damage caused by extremely low temperatures.
“This research concludes that a multicellular organism can be frozen and preserved as such for thousands of years and then come back to life, which is the dream of many science fiction writers. The more complex the organism of a living being, the more complicated it is to keep it alive frozen, and currently this is not possible for mammals,” added Malavin.
The ISTC researchers will continue to explore Arctic samples in search of other organisms capable of long-term cryptobiosis. They hope the knowledge about these small multicellular animals will provide clues on how best to preserve cells, tissues, and organs of other animals, including humans, in extreme cold.
This story was written in Spanish by Miguel Fernández in Cultura Colectiva News
