A peer-reviewed 2023 study found one Siberian permafrost nematode had remained frozen for about 46,000 years before thawing, reviving and reproducing asexually in the lab.
Genetic analysis identified it as a previously unknown species, Panagrolaimus kolymaensis, and its descendants were cultivated for more than 100 generations after the original worm survived only briefly.
Experiments suggest the worm endured deep freeze through cryptobiosis: mild dehydration triggered trehalose production, a sugar that helps protect cells, DNA and proteins from freezing and water loss.
Similar defenses in the lab worm C. elegans indicate the survival mechanism may be more widespread, while researchers are now probing the genes and proteins behind it.
The finding pushes the age record for revived microscopic animals back by several thousand years and could reshape how scientists think about long-term survival, evolution and extinction resilience.