A novel nematode species from the Siberian permafrost shares adaptive mechanisms for cryptobiotic survival with C. elegans dauer larva

Some organisms in nature have developed the ability to enter a state of suspended metabolism called cryptobiosis¹ when environmental conditions are unfavorable. This state-transition requires the execution of complex genetic and biochemical programs¹^,²^,³, that enables the organism to survive for prolonged periods. Recently, nematode individuals have been reanimated from Siberian permafrost after remaining in cryptobiosis. Preliminary analysis indicates that these nematodes belong to the genera <em>Panagrolaimus</em> and <em>Plectus</em>⁴. Here, we present precise radiocarbon dating indicating that the <em>Panagrolaimus</em> individuals have remained in cryptobiosis since the late Pleistocene (~46,000 years). Phylogenetic inference based on our genome assembly and a detailed morphological analysis demonstrate that they belong to an undescribed species, which we named <em>Panagrolaimus n. sp</em>. Comparative genome analysis revealed that the molecular toolkit for cryptobiosis in <em>Panagrolaimus n. sp. </em>and in <em>C. elegans</em> is partly orthologous. We show that biochemical mechanisms employed by these two species to survive desiccation and freezing under laboratory conditions are similar. Our experimental evidence also reveals that <em>C. elegans</em> 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.