Thawed by Russian researchers, the small asexual invertebrate – known as a bdelloid rotifer – was able to reproduce in the laboratory
In the animal world, bdelloid rotifers are known for their prodigious ability to survive extremely low temperatures.
Not surprisingly, researchers have already observed that, when frozen between −20 °C to 0 °C, these small freshwater invertebrates can survive for six to ten years.
But an ancient bdelloid recently recovered from Siberian permafrost suggests that this time span may actually be in the thousands:
After being frozen for around 24,000 years, the animal “came back to life”. The case, described in the journal Current Biology in publication this Monday (7), is the oldest report of rotifer survival in a frozen state.
The discovery was led by the Soil Cryology Laboratory of the Institute of Physico-Chemical and Biological Problems in Soil Sciences, located in Pushchino, Russia.
There, researchers are used to isolating microscopic organisms that were extracted through drilling in ancient Siberian permafrost – a perennial layer of ice.
Single-celled microbes, nematode worms, moss stalks and Lychnis coronaria plants are among the creatures identified by the team that have also “awakened” from the ice.
It was using the radiocarbon dating technique that the group discovered that, surprisingly, the newly collected rotifer was, on average, no less than 24 thousand years old.
“Our report is the most concrete proof to date that multicellular animals can endure tens of thousands of years in cryptobiosis, the state of almost completely interrupted metabolism”, says Stas Malavin, who co-led the project, in a statement.
The state of cryptobiosis is a mode of latency temporarily adopted by some animals when faced with adverse environmental conditions.
It is as if they pressed a “pause” button on all their metabolic processes until external circumstances return to normal.
This is what the ancestral rotifer did (thawed):
Once thawed in the laboratory, the animal began to reproduce continuously, in a process known as parthenogenesis — a form of asexual reproduction.
By freezing and thawing dozens of these rotifers, scientists discovered that the organisms can withstand the formation of ice crystals — which occurs during slow freezing — for at least seven days.
This suggests that these invertebrates have some mechanism capable of protecting their cells and organs from long-term damage caused by excessively low temperatures.
According to the researchers, unraveling these protective mechanisms can help to understand the biological functioning of rotifers with greater precision.
But not only that: these tiny animals could provide clues about the best ways to preserve cultures of cells, tissues and organs from other animals — including humans.
“Of course, the more complex the organism, the more difficult it is to preserve it alive in frozen form, and for mammals it is not currently possible,” notes Malavin.
“However, going from a single-celled organism to an organism with an intestine and a brain [capable of surviving ice], although microscopic, is a big step forward”, says the scientist.