Scientists unravel the mystery of the most tenacious creature on Earth by looking into its genome
Silent worms are microscopic invertebrates known for their ability to survive and reproduce even under the most unfavorable conditions: in darkness, extreme cold and heat, high pressure, very salty environments, and even in a space vacuum. Scientists have been able to decipher one of their superpowers – the ability to easily tolerate the complete absence of water.
Details of the opening
Although they cannot be seen with the naked eye, they live everywhere – in sea and fresh water, on land, and even in the ice-covered Antarctic. They can also be found in radiation-contaminated areas, as they can easily tolerate such conditions.
Previous studies have shown that a unique set of genes allows the moths to survive in conditions unbearable for other organisms, so scientists have begun to decipher the genome of these amazing creatures.
A team from the UK, Norway, and Japan studied the genes responsible for anhydrobiosis, a state of dormancy that silent animals enter to conserve the last of their water resources when they are almost completely dry. This allows them to stop metabolizing until the situation around them becomes favorable again, even if it takes decades. After that, they restart the metabolic process, replenish moisture reserves, and live on.
The genes that regulate this process are located in different parts of the cell, and a distinctive feature of at least some species of silent worms is that there are two sets of genes at once. Like some other animals, they also have a gene for stress resistance.
To understand how such a genome evolved and where such resilient creatures came from, scientists identified and analyzed gene sequences from 13 genera of moths. The sample includes representatives of two main classes of this type – Heterotardigrada and Eutardigrada.
Initially, they speculated that resistance to desiccation probably arose as an adaptation to the terrestrial environment when silent marine species began to spread beyond marine waters. But in reality, they discovered a complex network of genetic intertwining, some links of which were duplicated in some species, and in others they were absent altogether. At the same time, the effectiveness of anhydrobiotic treatment does not always depend on the types and number of genes that seem to be associated with it.
The researchers left further “unraveling” of the genome for the future, but the information obtained was enough to restore the main chain of evolution of the slow-moving animals.
- First, we managed to confirm the hypothesis that the common ancestor of all slow-moving animals once had to adapt to life offshore, and that it had some of the genes responsible for saving them from drought. Perhaps this happened during the resettlement to freshwater bodies, where there is water, but unlike the sea, there is also a risk of shallowing and drying up.
- In addition, the analysis showed that different species of moths received some of these genes after separation from a single common ancestor. This is indicated by different sets of genes and different behavior of proteins in different species – for example, in some species they turn into granules when dried, and in others into thin threads. Thus, the development of resilience to extremely dry conditions took place in at least two stages.
What exactly do silent movers do to survive
In a new paper, a team of researchers claims to have discovered at least one of the chemical switches that allows for anabiosis, also called “tune.”
In a series of experiments, evidence has been found that reactive oxygen species (ROS) seem to play an important role in mediating the tune process.
The researchers found that in silent moths, ROS seem to signal the oxidation of the amino acid cysteine, which in turn is crucial for tune formation. And when the team found a way to turn off the ability to oxidize cysteine in their tiny subjects, the noctules instantly lost their ability to tune.
These specific findings are based on the study of only one species, Hypsibius exemplaris. And even if this study stands up to further scrutiny by independent experts, the researchers realize that this is only the beginning of their work. The fact is that not all species of these creatures succumb to tuning-some later species use other survival strategies that have yet to be explored.
