They are the toughest known animals on Earth and now the secret to one of their superpowers – resistance to radiation – is out.

Tardigrades, also known as water bears or moss piglets, are tiny, eight-legged creatures that live in small bodies of water in habitats such as moss across the planet and are renowned for their extreme survival skills. They can survive in the vacuum of outer space, withstand temperatures ranging from close to absolute zero to nearly 100°C, cope with pressures six times greater than those at the bottom of the deepest ocean and survive dehydration and being frozen for years on end. They can also defy hefty amounts of radiation that would be lethal to most other life on the planet – and now we know how they do it.

It is mainly down to a bizarre protective protein they evolved that somehow shields their DNA from radiation damage. Short for “Damage suppressor”, Dsup appears to work by physically cuddling up to DNA and cocooning it from harm, but without disrupting its normal functions. It may also help by somehow mopping up DNA-damaging agents called reactive oxygen species.

Five Reasons Why Tardigrades Are The Toughest Animal

1. Tardigrades change form to survive without water: In extreme conditions, tardigrades can dry out completely, replacing almost of the water in their bodies with a sugar called trehalose. As a result, they’re able to survive environments that would otherwise kill them.

2. Tardigrades’ minuscule size hides them from predators: For all their resilience, the tardigrade is one of nature’s smallest creatures. Barely the size of a poppy seed at less than 1.5 millimeters long, the tardigrade can exist hidden in sediments and seas, unnoticed by potential predators.

3. Tardigrades’ mouths contain sharp daggers: Though they may be little, they are fierce! The tardigrade’s mouth is a serious weapon, its dagger-like teeth used to spear algae and even other small animals.

4. Tardigrades traveled to space – and survived: To test the true resilience of tardigrades, Swedish researcher K. Ingemar Jonsson from Kristianstad University launched tardigrades into space on the FOTON-M3 spacecraft on low-Earth orbit in 2007. Exposed to open space conditions, most of the tardigrades survived exposure to vacuum and cosmic rays, with some even surviving deadly levels of UV radiation.

5. They’ve been around longer than nearly every other living organism: Tardigrades roamed the earth and seas far before humans did – and will most likely outlast us. Will the tardigrades be nature’s last organisms standing? Only time will tell.
(Source: National Geographic)

A 2015 study concluded that tardigrades had scavenged up to one-sixth of their DNA — and many of their protective genes — from bacteria and other organisms by a process called horizontal gene transfer. It was unclear how they would have done that, but we do know that their DNA breaks into small pieces when they are desiccated, while their nucleus becomes leaky when they rehydrate, perhaps allowing the entry of foreign DNA that could then mix with the water bear’s own genes.

We know horizontal transfer happens occasionally , but most cases involve less than 1 per cent of an organism’s genes. If water bears could really steal such a large proportion of DNA from other organisms, this would change how we think about evolution and the inheritance of genetic material: the tree of life would become a web with genes crossing between branches. But that evidence was disputed earlier this year — the putative foreign DNA may have just been the result of sample contamination. That study found instead that water bears have only around 1 per cent of foreign genes, as one would expect.