Russian researchers report that they isolated from permafrost a microscopic organism dating back about 24,000 years that they observed and reproduced in the laboratory. They report their work in an article published on June 7, 2021, in the journal Current Biology.
The animal in question is between 0.1 and 2 millimeters in size, but it truly represents a scale model of complex animals. Indeed, it has a constant number of cells, from birth to death, about a thousand. It has a brain made up of 150 to 200 neurons, multiple sensory organs, striated muscles, a stomach, and even jaws (trophi) housed in a pharynx called a mastax.
This microscopic multicellular organism, therefore, has everything a large one, because it contains, in an extremely limited volume, all the devices which are usually endowed with any multicellular animal. Their name: Bdelloïdes rotifers (fère: porte, roti: wheels). Why this denomination? Simply because the ciliary beating motion of their anterior rotator apparatus resembles two wheels.
Absence of any male among the Bdelloids
These organisms can survive in slowed-down life (cryptobiosis) for months or even years, only to revive in water. Their usual lifespan is only three to six weeks. More than 460 species of Bdelloids have been identified to date.
Surprisingly, no male has ever been observed. And for good reason: these rotifers reproduce exclusively through a process called obligatory parthenogenesis. Their descendants are natural clones. In other words, there are therefore only females, capable of reproducing on their own. You don't need a male for reproduction.
Most Bdelloïdes rotifers live in mosses or lichens, sometimes in plankton or forest humus, in environments that often dry out. The Bdelloids do the same and manage to survive in cryptobiosis. These tiny animals can then withstand extremely low temperatures. The survival of Bdelloïdes rotifers six to ten years after freezing between -20 ° C and 0 ° C has already been described. This time, Lyubov Shmakova, Stas Malavin, and their colleagues from the Institute of Physicochemical and Biological Problems of Soil Sciences (Pushchino, 120 km south of Moscow), report the survival of a Bdelloïde rotifer discovered in permafrost from northeastern Siberia.
Radiocarbon dating by accelerator mass spectrometry has made it possible to date this sample taken at a depth of 3.5 meters below the surface in the middle layers of the bed of the Alazeïa river. This material frozen in permafrost (also known as permafrost) dates from a period between 23,960 years and 24,485 years. "This is the longest observed survival of frozen rotifers," Russian scientists say. He added that the tiny organism discovered in permafrost is indeed a rotifer, as evidenced by the sequencing of actin genes (muscle molecule) and the comparison with the genome of contemporary isolates of rotifers.
Russian researchers indicate that this rotifer tolerated being frozen at a temperature of about - 15 ° C for a week. After that, biologists observed that it was able to reproduce continuously in the laboratory by obligatory parthenogenesis. A month later, they obtained several live rotifers. Several secondary cultures were thus obtained, these animals reproducing, as has been said, in a mode not involving any male.
Analyzes were then undertaken on this progeny. Analysis of the COX1 gene from three rotifers present in secondary cultures also confirmed that they were phylogenetically related to current Adineta isolates. It appears that these organisms are related to a contemporary isolate of Bdelloïde collected in Belgium: Adineta vaga.
Other organisms capable of surviving in frozen soils
The revival of a rotifer kept frozen for about 24,000 years is not the only example of organisms able to survive in habitats frozen for many years.
In 2018, Russian researchers (Pouchtchino) reported that nematodes contained in the permafrost of two localities in northeast Siberia had come back to life. These worms survived in frozen soils for 30,000 years.
Bryophytes (mosses) are also able to survive for many years in a state of latency. In 2013, Canadian researchers at the University of Alberta (Edmonton) reported resuscitating bryophytes trapped in ice for 400 years.
Finally, in 2012, a Russian team (Pouchtchino) reported the regeneration of a small herbaceous plant of the genus silenus and the Caryophyllaceae family (Silene stenophylla) from fruits preserved in a layer of Siberian permafrost, located 38 meters below the surface and dated 30,000 years ago. The plants have been tested for their sexual fertility. It should be noted that S. stenophylla requires cross-fertilization for sexual reproduction to take place. Most incredible is that flowers from these ancient plants were able to be fertilized artificially with pollen, also from permafrost and from other ancient plants. Eight to nine weeks passed between artificial pollination of the flowers and the ripening of the first seeds. The germination in the laboratory of the seeds taken from the old plants that had come back to life was 100%!
Marc Gozlan (Follow me on Twitter, Facebook, LinkedIn)
To know more :
Shmakova L, Malvin S, Yakovenko N, et al. A living bdelloid rotifer from 24,000-year-old Arctic permafrost. Curr Biol. 2021 Jun 7; 31: R697 – R713. DOI: 10.1016 / j.cub.2021.04.077
Shatilovich AV, Tchesunov AV, Neretina TV, Grabarnik IP, Gubin SV, Vishnivetskaya TA, Onstott TC, Rivkina EM. Viable Nematodes from Late Pleistocene Permafrost of the Kolyma River Lowland. Dokl Biol Sci. 2018 May; 480 (1): 100-102. doi: 10.1134 / S0012496618030079
Shain DH, Halldórsdóttir K, Pálsson F, et al. Colonization of maritime glacier ice by bdelloid Rotifera. Mol Phylogenet Evol. 2016 May; 98: 280-7. DOI: 10.1016 / j.ympev.2016.02.020
Iakovenko NS, Smykla J, Convey P, et al. Antarctic bdelloid rotifers: diversity, endemism, and evolution. Hydrobiologia. 2015; 761.5–43.
La Farge C, Williams KH, England JH. Regeneration of Little Ice Age bryophytes emerging from a polar glacier with implications of totipotency in extreme environments. Proc Natl Acad Sci U S A. 2013 Jun 11; 110 (24): 9839-44. DOI: 10.1073 / pans.1304199110
Yashina S, Gubin S, Maksimovich S, et al. Regeneration of whole fertile plants from 30,000-y-old fruit tissue buried in Siberian permafrost. Proc Natl Acad Sci U S A. 2012 Mar 6; 109 (10): 4008-13. DOI: 10.1073 / pans.1118386109
Newsham KK, Maslen NR, McInnes SJ. Survival of antarctic soil metazoans at -80 degree C for six years. Cryo Letters. 2006 Sep-Oct; 27 (5): 291-4. PMID: 17256060
On the Web :
Les Rotifères (Catholic University of Louvain, 2017)
Pierre Clement. Rotifers, Epigenetics and Evolution. Bulletin of the Zoological Society of France. 2009; 134 (3- 4): 203-24.
Pourriot R, Francez AJ. Practical introduction to the systematics of organisms in French continental waters. - 8: Rotifères. Publications of the Société Linnéenne de Lyon. 1986; 55-5: 148-76.
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