the snail with iron armor

the snail with iron armor

A golden snail with a foot made of iron scales looks like a sci-fi creature. But in some remote parts of the Indian Ocean, these snails are very real.

“It looks like an armored knight crawling on the deep-sea floor,” says Julia Sigwart, a biologist at Frankfurt’s Senckenberg Research Institute and one of the few people to study a living scale snail (Chrysomallon squamiferum)also known as a sea pangolin.

The habitat of the snails is extreme. They live several miles below the ocean’s surface at scorching hydrothermal vents that are bathed in toxic chemicals and can reach temperatures in excess of 300 °C (572 °F).

The ocean is one of the last truly wild places on earth. It is teeming with fascinating species that sometimes border on the absurd, from fish that peer upwards through transparent heads to golden snails with iron shells. We know more about outer space than the deep oceans, and science is only just beginning to scratch the surface of the rich diversity of life below.

As mining companies push to industrialize the seabed and global leaders continue to bicker over how to protect the high seas, a new Guardian Seascape series will showcase some of the weird, wonderful, majestic, ridiculous, tough and overwhelming creatures recently discovered. They show how much there is still to learn about the world’s least-known environment – and how much needs to be protected.

The snails’ entire body and lifestyle revolves around bacteria that grow in a special sac in their throats, which convert chemicals pouring out of the vents into energy, thus providing all of the snails’ food.

To keep their microbes well fed, scalefoot snails evolved huge gills to take in oxygen and chemicals from seawater and then release them through their bloodstream and an enormously spacious heart. A human heart of appropriate proportions would be as big as our head.

When you say a species is on the verge of extinction, everyone understands

Julia Sigwart, biologist

In 2019, scientists found that the scales on the snails’ base are not designed to protect against predatory attacks, but to ward off a toxic threat that comes from within. The bacteria hiding in a scalefoot snail’s throat release sulfur as a waste product that is deadly to snails (it’s a common active ingredient in snail and snail-killing pellets).

The internal structure of their scales acts like tiny exhaust pipes, drawing the dangerous sulfur from the snail’s soft tissue and depositing it outside as a harmless iron-based compound.

Although they have evolved many strange adaptations to survive on vents, scalefoot snails have not counted on humans showing interest in their habitat. All three of the sites they live in — an area less than 0.025 square kilometers (0.01 sq mi) that together would fit in St. Peter’s Square in Vatican City — are potential targets for deep-sea mining.

Mining companies are after gold, silver and other precious metals or rare metals that are deposited in the rock faces of black smoker chimneys. If their tiny habitats were damaged or destroyed, the scale foot snails would soon be gone.

Because of this, Sigwart and her team set out to assess the status of these rare animals, eventually having the scale snail listed as an endangered species on the International Union for Conservation of Nature Red List.

“It’s an incredibly powerful communication tool,” she says. “When you say a species is in danger of extinction, everyone in the world understands it.”

The scalefoot snail was the first species in the world to be listed as threatened due to deep-sea mining, but there are now many deep-sea molluscs that experts have assessed and placed on the world’s endangered species list.

Related: Deep-sea mining could wipe out hundreds of species, researchers warn

Of 184 endemic species living only on vents, from giant clams to a fuzzy snail named after Joe Strummer from The Clash, only 25 are considered non-extinct.

These species remain relatively safe, Sigwart explains, because they live in vent fields where future deep-sea mining development is specifically prohibited. These include marine protected areas in Canada’s territorial waters and around the Azores.

Most other species live on offshore hydrothermal vents that lie outside territorial limits and are therefore less protected and more open to mining exploration.

“These are Red List assessments that reflect the status and risk to the entire species and its potential to actually go extinct and lose us entirely,” says Sigwart, “and nobody wants that.”

For Sigwart, these unusual mollusks brilliantly illustrate that evolution is all about being good enough to get by. “It shows us the strange and tortuous paths life can take to adapt and survive,” she says.

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