With 24,000 years frozen in the Siberian permafrost, it is undoubtedly the longest surviving case of bdelloid rotifers , thanks to the fact that they paused their metabolism for millennia.
This microscopic creature that is found both in fresh water (ponds, streams …) and in damp ground (moss, lichens, tree bark …) and that can move by swimming or crawling, has proven to be an “evolutionary scandal” for having thrived for millions of years without having sex; persist for at least 24,000 years in Siberian permafrost and then be able to reproduce.
These multicellular invertebrates that are exclusively female , are recognized for their resistance to radiation and their ability to withstand quite inhospitable environments as occurs with other equally striking creatures such as tardigrades: extreme acidity, dehydration, starvation and little oxygen.
The toughest animals in the world?
They have existed for at least 50 million years and can also come back to life after tens of thousands of years in freezing, according to a study published in the journal Current Biology, whose findings also show that these robust microanimals can also withstand extreme durations of suspended animation.
For the study, the scientists collected samples by drilling roughly 3.5 meters below the surface of the permafrost in northeastern Siberia where radiocarbon dating showed the soil to be around 24,000 years old. They discovered live bdelloid rotifers encased in ancient permafrost, whose average temperature is around -10 ° C.
While simple organisms like bacteria can often survive millennia in permafrost, “this is an animal with a nervous system and a brain and all,” says Stas Malavin of the Pushchino Scientific Center for Biological Research RAS in Russia. Rotifers were not known to last that long.
The researchers used accelerator mass spectrometry to date the organic debris found with the rotifer. They were between 23,960 and 24,485 years old, suggesting that the rotifer froze in permafrost at the same time. Modern rotifers appear to have a similar ability to survive freezing.
The team froze individuals of different modern species, as well as some of the descendants of the ancient rotifer, at -15 ° C for a week. Both groups were equally tolerant of freezing, with similar survival rates; that is, once the thawed survivors began cloning themselves, scientists were unable to discern which were old and which were newborn , as the rotifers were genetically identical. How do they do that? The truth is that it is not clear. There are still many things that we do not know about them.
“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 fiction writers,” adds Malavin. “Of course , the more complex the organism, the more difficult it is to keep it alive frozen and, for mammals, it is currently not possible. However, going from a unicellular organism to an organism with intestine and brain, although microscopic, is a great step forward “, concludes the expert.
Referencia: Current Biology, Shmakova et al.: “A Living Bdelloid Rotifer Recovered from 20,000 Year Old Arctic Permafrost” www.cell.com/current-biology/f … 0960-9822(21)00624-2 , DOI: 10.1016/j.cub.2021.04.077
