Nematodes survived in Siberian permafrost for 46,000 years

In 2018, an extraordinary discovery was made by researchers from the Institute of Physicochemical and Biological Problems in Soil Science RAS in Russia. They found two roundworm species (nematodes) in the Siberian Permafrost that had been in cryptobiosis for an astonishing 46,000 years, dating back to the late Pleistocene. This ability to enter a dormant state and survive harsh conditions is an intriguing trait seen in some organisms like tardigrades, rotifers, and nematodes.

Upon thawing the worms in the lab, the researchers were able to confirm their ancient origins through radiocarbon dating of the surrounding plant material. These nematodes, buried 40 meters below the surface in frozen deposits, had not seen thawing for tens of thousands of years.

Another group of scientists from the Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG) in Dresden, Germany, had already been investigating how larval stages of the nematode Caenorhabditis elegans could endure extreme conditions. When they learned about the permafrost nematodes, they reached out to collaborate with the Russian team.

The researchers in Dresden successfully sequenced and analyzed the genome of one of the permafrost nematodes, which turned out to belong to a previously unknown species they named “Panagrolaimus kolymaensis,” named after the Kolyma River region where it was found.

Interestingly, through comparing the genome of Panagrolaimus kolymaensis with that of the well-studied model nematode Caenorhabditis elegans, the researchers identified shared genes that are involved in cryptobiosis. Most of the genes necessary for entering cryptobiosis in Caenorhabditis elegans were also present in Panagrolaimus kolymaensis.

Furthermore, the team discovered that mild dehydration exposure before freezing helped Panagrolaimus kolymaensis worms prepare for cryptobiosis and increased their survival when exposed to freezing temperatures of -80° Celsius. Both species produced a sugar called trehalose when mildly dehydrated, a factor that possibly enables them to endure freezing and extreme dehydration.

Remarkably, Caenorhabditis elegans larvae exposed to this treatment remained viable for an impressive 480 days at -80° Celsius without suffering any adverse effects on viability or reproduction after thawing.

The findings from this study shed light on the remarkable mechanisms that nematodes possess to endure cryptobiosis and survive for such long periods. These insights into their adaptation to extreme environments can have broader implications for understanding evolutionary processes and developing conservation strategies in the face of global warming.

Overall, this research extends the known record of cryptobiosis in nematodes by tens of thousands of years and offers fascinating prospects for further exploration and understanding of these resilient organisms.

Source: Max Planck Society

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