Scientists discover weakness of near-indestructible tardigrade

Tardigrades – the microscopic eight-legged animals – have been found to ‘hitch a ride’ on the backs of land snails, according to a new study.

However, researchers at Poland’s Adam Mickiewicz University also discovered that the near-indestructible creatures are less likely to survive when covered in snail slime.

Also known as water bears, tardigrades can live in extreme environments – including outer space – that would kill most other forms of life.

Finding a weakness in the animals is, therefore, uncommon – but experts believe snail mucus could be that rarity.

The new research saw Zofia Ksiazkiewicz and Milena Roszkowska, of Adam Mickiewicz University, place tardigrades in the middle of a box to see if they could cross a surrounding barrier on their own. They then compared this movement to when a land snail was allowed to move over them.

Left alone, tardigrades were not able to move outside the barrier but when they stuck themselves to land snails they were moved significantly, the academics noted.

They concluded that land snails could effectively aid the transfer of tardigrades – which, on average, measure around 0.5mm in length – to a new environment.

In a separate experiment, tardigrades were rehydrated after anhydrobiosis and some were exposed to snail mucus.

Anhydrobiosis is an ability that tardigrades have, whereby they can tolerate almost complete dehydration for years until water is available to them again. It is one of the characteristics that enables them to survive extreme conditions.

Researchers found that 98 per cent of the animals not exposed to snail mucus survived, compared with 34 per cent who were covered in the slime.

Ultimately, they deduced that snails may help tardigrades by moving them to new areas – but may also negatively affect tardigrades by reducing their chances of survival.

Writing in the journal Scientific Reports, the authors said: “Results of our experiments support the assumption that snails may transfer active tardigrades for short distances.

“On the other hand, the effect of the snails’ mucus on tardigrade recovery to active life after anhydrobiosis was negative.”

And they added: “Death rates of tardigrades in anhydrobiosis (tun) were higher when affected by mucus compared to mucus-free tuns.”

The breakthrough comes two years after a group of scientists at the University of Copenhagen discovered that the tiny animals struggle to survive in hot water.

Tardigrades can live in fresh and salt water, as well as on land, but need water in particular to live actively.

This research suggested that the creatures “rapidly wilt” in hot conditions, with water temperatures of almost 38C (100F) found to be able to kill some tardigrades in just one day.

With global temperatures rising due to the climate crisis, the authors warned at the time this could quickly become a serious problem for tardigrades, despite their ability to survive being frozen in ice for several years – with no oxygen – and be exposed to cosmic rays in outer space.