Bake them, freeze them, shoot them with a gun, or send them into space: silent octopuses can survive just about anything. Some experts even believe this micro-animal octopus could outlive every other species on Earth, including humans, until the sun dies.
If you went into outer space without protection, you would die. But a tiny animal no more than 1mm long – the size of a stiletto – survived this and much more. Under a microscope, silent fish, also known as water bears or moss piglets, look intimidating. Their chubby deformed faces, ferocious claws and dagger-like teeth make them look more like a monster from Dr Who than an animal.
Scientists are now trying to use their superpowers for our own legs, which include insects and crustaceans, scientists have not yet determined how to categorise these creatures in the animal kingdom.
Quietwalkers like to hide in moist environments where moss, lichens and leaves abound. You may even find them in your garden. But they are also known for being able to survive in extremely inhospitable places. They have been found in the Himalayas, on the ocean floor, in Antarctica and even in very acidic Japanese hot springs, although this discovery has yet to be confirmed.
Quietwalkers can live in more than just harsh environments on Earth. In 2007, these creatures became the first known animals to survive after being sent into space.
When the satellite they flew on returned to Earth, scientists found that many, though not all, had survived. Some females had even laid eggs in space, and they had just hatched 0° C and freezing to 0.01° C above absolute zero.
In 2021, scientists even released bullets with the silentwalkers inside to see if they could survive the impact. Studies have shown that the silent bullets can survive up to 900 m/s (3,000 km/h), which is faster than a bullet fired from a regular gun.
So how do these seemingly weak creatures manage to survive in such extreme conditions, and how did they develop these superpowers? It turns out that the silent creatures have a lot of tricks up their sleeves.
Life on pause
One of the extreme states to which the silent gaiters have evolved to is drying (essentially, desiccation). For most animals, life without water is absolutely impossible. When cells dry out, the membranes that hold them together shrink and lose volume.
All this, the scientist found that when a silent fish dries out, it sucks in its head and eight legs before entering a deep state of anabiosis that is very similar to death.
“They literally pack their organs, concentrating them in an extremely small confined space,” said Nadja Mebjerg, associate professor of cell biology and physiology at the University of Copenhagen.
In this state, the silent fish’s metabolism slows to 0.01 per cent of its normal rate. It can remain in this state for decades, recovering only when exposed to water.
For example, in 1948, Italian zoologist Tina Franceschi took a pacifier that had been collecting dust in a museum for more than 120 years and added water, after which one of the creatures began to move its paw. Although the creature never fully revived, in 1995 scientists were able to bring back to life the pacifers dried for his colleagues further investigated the mechanism of how pacifers survive by losing all the water in their bodies.
They found that a type of TDP known as cytoplasmically abundant heat-soluble proteins (CAHS) is responsible for this. When TDPs are surrounded by water, they have a jelly-like consistency and don’t fold into three-dimensional structures like normal proteins. But when they dry out, these proteins turn into a semi-solid gel that softens the cellular content, holding it in place.
“When the quiescents start to dry out, they start producing these proteins in very, very large quantities, essentially filling the inside of their cells with these strange, disordered, soft proteins,” Boothby explains.
“The proteins float in the liquid at first, but when the cell dries out, they actually clump together and form t;barrels” can survive being heated to 125°C for a few minutes. In the 1920s, Benedictine monk Gilbert Franz Rahm brought the silentworms back to life by heating them to 151° C for 15 minutes. However, the quietflies can only do this when they are hiding in a “barrel”.
“Many species of pacifers can survive temperatures well above 100° C, but they only do so when they are dry,” Boothby says.” If you have a tychochodon in a drop of water, and you heat that water to very high levels, the tychochodon will die almost as easily as any other organism.”
In fact, while pacifers are known for their resilience in certain situations, they tend to be vulnerable to high temperatures, suggesting that even they could suffer from the effects of climate change. Møbjerg’s study found that P. Therefore, it is assumed that they must have other defence mechanisms.
In 2016, a team of scientists from Japan revived the silkworms that had been frozen in Antarctica for 30 years. The two quietflies in the sample were named SB-1 and SB-2 (SB stands for Sleeping Beauty), respectively.
Freezing is particularly dangerous for living things because at low temperatures, cell membranes lose flexibility and become more fragile. The biggest danger, however, is ice crystals.
“Crystals are really harmful to cells because they’re sharp,” Boothby says. “They can pierce membranes, break down proteins or destroy nucleic acids such as DNA, the backbone of the cell.”
Even so, some quiescents can tolerate freezing to temperatures just above absolute zero (-273.15 y, the question of how quiescents survive irradiation has a better answer. In 2016, Kunieda and his team discovered a protein known as Dsup (damage-suppressing protein) that wraps around DNA like a blanket, protecting it from the harmful effects of ionising radiation. Moreover, the researchers synthesised human cells so that they could also produce Dsup. They then irradiated these cells with X-rays and found that Dsup prevented the breakdown of human DNA.
“Radiation can damage DNA directly, but most biological damage occurs indirectly,” says Kunieda. For example, radiation energy is absorbed by water molecules, which break down to form highly toxic molecules known as reactive oxygen species (AFCs). The AFC then attacks DNA and destroys it.
To prevent it from breaking down in response to radiation.
Meanwhile, in 2024, a separate group of researchers in France discovered a second protein called TDR1, which also appears to bind to DNA and protect it from radiation damage. The study showed that the pacifers can also repair their own DNA, which is another handy tool to help them cope with radiation.
Survival lessons for humans
In recent years, we’ve learnt more about pacifers, and some researchers have begun to wonder how their unusual properties could be used to help humans. Some scientists, for example, are hoping to use their knowledge of quiescents to protect people with cancer from the harmful effects of radiation therapy.
Radiation therapy is a treatment method that uses high-energy no healthy tissue survived.
However, more research is needed to understand how the mammalian immune system reacts to such proteins before the treatment can be used in humans, as Dsup would be labelled by the human body’s immune system as a disruptor.
Scientists believe there may be other ways to utilise the superpowers of silent mammals to help humans. For example, in addition to protecting the cells of the quiescent fish, TDPs could help preserve vaccines or other sensitive biological materials that need to be stored for long periods of time.
Take, for example, haemophilia, a rare blood-clotting disorder. People with this disease can die from bleeding if they are in a car accident or injured.
To stop this, they are given the human clotting protein Factor VIII, which