Roundworms Revived After Being Frozen in Ice for 42,000 Years
For the first time dormant multicellular organisms’ nematodes were revived after being buried in permafrost deposits for thousands of years.
In quite an interesting discovery made by a team of Russian researchers, ancient roundworms (also called nematodes) which had solidified in Siberian permafrost about 42,000 years ago and were frozen since then have come to life again. They existed in late Pleistocene epoch — Ice Age and have been frozen since then. Permafrost is a ground which stays at or below freezing point of water (zero degrees Celsius) continuously for at least two or more years. Such permafrost is mostly located in high altitudes like in and around Arctic and Antarctica regions of the planet. In this study, samples in permafrost were drilled from the frigid ground in north eastern region called Yakutia - coldest part of Russia. Two female roundworms were revived from a large block of ice - which contained around 300 roundworms. One of the two worms is thought to be around 32,000 years old (based upon carbon dating) and came from a soil sample taken from a squirrel burrow 100 feet below ground in the permafrost. The other one, believed to be around 47,000 years old, was found embedded in a glacial deposit just 11 feet below the surface near Alazeya River. Permafrost sediments contain a variety of unicellular organisms – like several bacteria, green algae, yeast, amoebas, moss - which survive for thousands of years in cryptobiosis. Cryptobiosis is defined as a metabolic state entered by an organism when coping with hostile environmental conditions such as dehydration, freezing, and lack of oxygen. These unicellular organisms have been seen to grow again after long-term natural ‘cryopreservation’. Cryopreservation is a process which can preserve and maintain biological living organelles, cells and tissues by cooling them at extremely low cryogenic temperatures. This procedure preserves the fine internal structure of cells thus resulting in better survival and maintained functionality.
The study published in Doklady Biological Sciences shows for the very first time, capability of a multicellular organism like worm to enter a state of cryptobiosis and remain frozen in permafrost deposits in the Arctic. The samples were isolated and stored in laboratory at around -20 degrees Celsius. The samples were thawed (or “defrosted”) and warmed up to about 20 degrees Celsius in Petri dishes containing enriched culture to boost growth. After several weeks, two roundworms woke up from their ‘longest nap’ and started showing signs of life like normal movement and even started looking for a meal. This can be deemed possible because of some ‘adaptive mechanism’ by these nematodes. The pair of worms can be called as the oldest living organism on Earth, their age being an average of 42000 years!
The study clearly demonstrates the ability of multicellular organisms to survive long-term cryptobiosis under conditions of natural cryopreservation. Another unique factor is that for the first time this hypothesis has been proven on a record length time-scale as all previous studies have shown that nematodes could survive in extreme environments like freezing temperatures for at least 25 years. There is a strong possibility that other multicellular organisms, including humans, could perhaps survive cryogenic preservation too.
Though it is now a common practice to ‘freeze’ one’s eggs, or semen for example, to bear children even when one becomes infertile. However, stem cells and other tissues which are very useful for conducting research cannot be preserved through this process. So, successful cryopreservation of different biological samples shall would be critical for any future clinical application or human trials. This technology has been strengthened in past decades with use of superior cryoprotective agents (which protect biological tissue from damage of freezing) and better temperature. Better understanding of freezing and thawing process can advance our understanding of cryopreservation. Cryogenic freezing remains a controversial topic and borders more towards science fiction. Any talk of an organism being ‘asleep’ for thousands of years and then springing back to life is baffling and surreal. Looking at this study, it seems like it can be a real and naturally occurring process, at least for worms. If no physical damage is done to the organism and their integrity is maintained in frozen environment then thawing should be possible. Around two decades ago, the same group of researchers had pulled spores and brought them back to life from a single-celled bacterium which were buried inside 250 million years old salt crystals, however, the work is still ongoing and requires more evidence. Such adaptive mechanism used by worms for instance can be of scientific importance for fields of cryomedicine and cryobiology.
A. V. Shatilovich et al. 2018, ‘Viable Nematodes from Late Pleistocene Permafrost of the Kolyma River Lowland’, Doklady Biological Sciences, vol. 480, no 1, DOI: https://doi.org/10.1134/S0012496618030079