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Curious organism trapped in permafrost for 24,000 years has been able to reproduce again

Permafrost is a gold mine for biologists, as it contains so many organisms trapped within its layer of ice. Recently, Russian researchers discovered a bdelloid rotifer in Siberian permafrost. This invertebrate – which reproduces exclusively by parthenogenesis – had been in stasis for more than 20,000 years, before waking up again and resuming its reproduction. An astonishing discovery which should help biologists to better understand cell cryopreservation.

A microscopic worm-like creature called an “evolutionary scandal” by biologists for thriving for millions of years without resorting to sexual reproduction, persisted for at least 24,000 years in Siberian permafrost, then has reproduced again, researchers have found.

Exclusively female multicellular invertebrates, the bdelloid rotifers (Adineta sp) are already renowned for their resistance to radiation and their ability to withstand rather inhospitable environments: dryness, starvation and lack of oxygen. They have also been around for at least 35 million years – and can be found today in freshwater lakes, ponds, streams, and moist terrestrial habitats such as moss, lichen, tree bark. and the ground.

A cryopreservation mechanism still uncertain

These tough little creatures – who have a complete digestive tract including a mouth and anus – are able to survive in harsh environments by shutting down all activity and shutting down their metabolism almost entirely. It’s called cryptobiosis, which means “hidden life,” says Stas Malavin, a researcher at the Soil Cryology Laboratory at the Institute of Physicochemical and Biological Problems in Soil Science in Pushchino, Russia.

The soil cryology laboratory has already isolated other microscopic organisms – including a 30,000-year-old nematode worm – from permafrost. But in this study, Malavin and his colleagues used radiocarbon dating to determine that the rotifers, recovered from samples collected in remote locations in the Arctic via a drilling rig, were around 24,000 years old. Previous evidence had shown that the creatures could survive for up to a decade when frozen.

A) Complete observation of the bdelloid rotifer specimen from the permafrost. B) Lateral view of the head. C) Trophi © Lyubov Shmakova et al. 2021

Rotifers found in the permafrost are believed to have been found under the feet of large woolly creatures – like the woolly rhino – which are now extinct, says Malavin. Once thawed in the lab, the rotifers were able to reproduce, the researchers write in the journal Current Biology. But the authors are unsure of the biological mechanisms that allow these tiny organisms to survive in ice for such a prolonged period.

Studying these creatures can help find ways to improve cryopreservation of cells, tissues and organs, the researchers suggest. ” Humans cannot conserve organs and tissues for such a long time. These rotifers, along with other organisms found in permafrost, represent the result of a great natural experiment that we cannot replicate … so they are good models for further study. », Explains Malavin.

Better understand the evolution of bdelloid rotifers

Matthew Cobb, professor of zoology at the University of Manchester who was not involved in this work, says the research’s most dramatic implication was that there could be all kinds of frozen animals in the permafrost that could wake up as global warming melts permafrost.

This doesn’t mean terrifying things are going to come out and eat us, but it does give scientists the opportunity to study how the rotifer has adapted to withstand the bad effects of frost, and the opportunity to explore the difference between species. existing and their predecessors Says Malavin.

This is particularly important in the case of bdelloid rotifers which reproduce by parthenogenesis (females clone each other). One of the advantages of sex is that you mix genes with each generation; here they are all copied, so there is less variability for natural selection to operate on. We now have the possibility to compare the genome of this group of animals with their modern equivalents, known from Belgium (Adineta valga). It will shed light on a key biological curiosity and could reveal why some animals have given up on sexual reproduction altogether. He adds.

Video showing the specimen of bdelloid rotifer from permafrost:

Sources: Current Biology

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