Microscopic Invertebrates Bring Back To Life After 24,000 Frozen Years – 6/10/2021 – Science

When inland Brazil was full of saber-teeth and giant sloths, at a time when humans hadn’t even reached America, the Siberian winter froze some microscopic invertebrates. After 24,000 years “in the refrigerator”, the animals were brought back to life by researchers from Russia and were even able to reproduce.

The feat, described in an article in the scientific journal Current Biology, is probably not that surprising to those who were familiar with the so-called Bdelloides rotifers, creatures that vaguely resemble a thermometer (the traditional ones, transparent and with mercury inside ) and measure about a tenth of a millimeter. They were already notorious for their ability to spend long periods of time in paused animation, but nothing compares to the record they have now set.

Bdelloid rotifers don’t look much more complicated than a digestive tract surrounded by cilia, but like us, they also have differentiated and specialized tissues, including a small brain. This means that discoveries about their ability to survive long periods of freezing could be useful in applying similar processes to larger organisms – to preserve organs longer for transplant, for example.

“The more complex the organism, the more difficult it is of course to keep it alive in a frozen state. This is not possible for mammals today, ”said the coordinator of the study, Stas Malavin, from the Institute for Physico-Chemical and Biological Problems of Soil Science in Pushchino, Russia. “But seeing that this is not only possible with unicellular organisms, but also with an organism with a digestive system and a brain, albeit microscopic, is a big step,” he said in an official statement.

The revived rotifers that Malavin and his colleagues studied belong to the genus Adineta and were collected in the so-called “permafrost” (permanently frozen Arctic soil) of the Alazeya river basin in northeast Siberia. The 3.5 m depth from which the samples were taken, as well as the presence of mummified mammals from the Ice Age and other geological evidence strongly suggest that invertebrates have indeed spent the past tens of thousands of years frozen.

The age of the samples – 24,485 years to be precise – was determined using the carbon-14 method, the most commonly used organic substance.

The researchers incubated the samples under more pleasant laboratory conditions than in permafrost and after a month discovered not only the rotifers but also various microbes. The presence of small animal genetic material in the soil prior to this point of cultivation confirms that they were present from the moment the piece of land was originally frozen.

After thawing, invertebrates did not waste time and began to reproduce – which is much easier in the case of rotifers, since they are animals that adopt a strict form of parthenogenesis, or “virginity,” a form of reproduction other than sex depends.

For example, a parthenogenetic lineage was established in the Russian laboratory, from which 144 individuals were selected and subjected to a final challenge. The rotifers were refrozen (at a temperature of 15 degrees Celsius for a week) and then brought back to room temperature. At least some survived the trial, but strangely enough, they proved no more successful at it than their modern relatives. This suggests that the Ice Age rotifers weren’t anything special – the impressive frost survivability would be something more general to the group.

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