Precise radiocarbon dating indicates that Panagrolaimus kolymaensis, a species of soil nematode new to science, remained in cryptobiosis for about 46,000 years, since the Late Pleistocene.
General morphology of Panagrolaimus kolymaensis, female. Image credit: Shatilovich et al., doi: 10.1371/journal.pgen.1010798.
“Organisms from diverse taxonomic groups can survive extreme environmental conditions, such as the complete absence of water or oxygen, high temperature, freezing, or extreme salinity,” said senior author Dr. Teymuras Kurzchalia from the Max Planck Institute for Molecular Cell Biology and Genetics and colleagues.
“The survival strategies of such organisms include a state known as suspended animation or cryptobiosis, in which they reduce metabolism to an undetectable level.”
“Spectacular examples of long-term cryptobiosis include a Bacillus spore that was preserved in the abdomen of bees buried in amber for 25 to 40 million years, and a 1,000- to 1,500-year-old Lotus seed, found in an ancient lake, that was subsequently able to germinate.”
“Metazoans such as tardigrades, rotifers, and nematodes are also known for remaining in cryptobiosis for prolonged periods.”
“The longest records of cryptobiosis in nematodes are reported for the Antarctic species Plectus murrayi (25.5 years in moss frozen at minus 20 degrees Celsius), and Tylenchus polyhypnus (39 years desiccated in an herbarium specimen).”
In their research, the authors revived two soil nematodes that were preserved in Siberian permafrost for about 46,000 years.
Initial observations provisionally described them as belonging to the genera Panagrolaimus and Plectus.
The researchers then sequenced the genome of a Panagrolaimus nematode and found that it represents a new species.
Through comparative analysis, they also found that the new species, named Panagrolaimus kolymaensis, and the model organism Caenorhabditis elegans utilize similar adaptive mechanisms to survive harsh environmental conditions for prolonged periods.
“To our surprise, most of the genes necessary for entering cryptobiosis in Caenorhabditis elegans dauer larvae were also present in Panagrolaimus kolymaensis,” they said.
“We evaluated the ability of Panagrolaimus kolymaensis to survive and discovered that mild dehydration exposure before freezing helped the worms prepare for cryptobiosis and increased survival at minus 80 degrees Celsius.”
“At a biochemical level, both species produced a sugar called trehalose when mildly dehydrated in the lab, possibly enabling them to endure freezing and intense dehydration.”
Caenorhabditis elegans larvae also benefited from this treatment, surviving for 480 days at minus 80 degrees Celsius without suffering any declines in viability or reproduction following thawing.
“We show that biochemical mechanisms employed by these two species to survive desiccation and freezing under laboratory conditions are similar,” the scientists said.
“Our experimental evidence also reveals that Caenorhabditis elegans dauer larvae can remain viable for longer periods in suspended animation than previously reported.”
“Altogether, our findings demonstrate that nematodes evolved mechanisms potentially allowing them to suspend life over geological time scales.”
The results were published online in the journal PLoS Genetics.
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A. Shatilovich et al. 2023. A novel nematode species from the Siberian permafrost shares adaptive mechanisms for cryptobiotic survival with C. elegans dauer larva. PLoS Genet 19 (7): e1010798; doi: 10.1371/journal.pgen.1010798
