A gold snail with a foot covered in iron scales looks like a science fiction creature. But in some remote parts of the Indian Ocean these snails are very real.
“It looks like an armored knight crawling across the bottom of the deep sea,” says Julia Sigwart, a biologist at the Senckenberg Research Institute in Frankfurt and one of the only people to have seen a living scaly-footed snail (Squamiferous chrysomal)also known as sea pangolin.
The habitat of the snails is extreme. They live several miles below the ocean’s surface on burning hydrothermal vents, which are immersed in toxic chemicals and can reach temperatures of over 300 ° C (572F).
The snails ‘entire body and lifestyle revolves around bacteria that grow inside a special pouch in their throat, which convert the chemicals escaping from the vents into energy and thus provide all the snails’ food. .
To keep their microbes well fed, scaly-footed snails have developed huge gills to absorb oxygen and chemicals from seawater, then distribute it through the bloodstream and an extremely capacious heart. A human heart of equivalent proportions would be the size of our heads.
In 2019, scientists discovered that the scales on the snails’ legs serve not to protect against predatory attacks but to ward off a toxic threat that comes from within. Bacteria hidden in the throat of a scaly-footed snail release sulfur as a waste product, which is deadly to snails (it’s a common active ingredient in snails and slug-killing pellets).
The internal structure of their scales acts as tiny exhaust pipes, drawing the dangerous sulfur away from the soft tissues of the snails and depositing it on the outside as a harmless iron-based compound.
Although they have developed many strange adaptations to survive the vents, the scaly-footed snails have not aimed at humans by showing interest in their habitat. All three sites they live in: an area of less than 0.025 sq km (0.01 square miles), which together would fit inside St. Peter’s Square in Vatican City, are potential targets for deep-sea mining.
Mining companies look for gold, silver and other precious or rare metals deposited in the rock faces of the black smoke chimneys. If their tiny habitat areas were damaged or destroyed, the scaly-footed snails would soon disappear.
That’s why Sigwart and his team began assessing the status of these rare animals and eventually added the scaly-footed snail to the International Union for Conservation of Nature’s red list as an endangered species.
“It’s an incredibly powerful communication tool,” he says. “When you say that a species is in danger, everyone in the world understands it.”
The scaly-footed 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 mollusks that experts have evaluated and added to the global list on the way. extinction.
Out of 184 endemic species that live only on vents, from giant clams to a hairy snail named after Joe Strummer of the Clash, only 25 are not considered endangered.
These species remain relatively safe, explains Sigwart, because they live in relief fields where there is an explicit ban on any future development of deep-sea mining. This includes marine protected areas in the territorial waters of Canada and around the Azores.
Most of the other species live on hydrothermal vents on the high seas, which are beyond territorial limits and therefore less protected and more open to mining exploration.
“These are the red list assessments that reflect the status and risk to the entire species and its potential to actually become extinct and for us to lose it completely,” says Sigwart, “and nobody wants that.”
For Sigwart, these unusual mollusks brilliantly illustrate how evolution is about being good enough to get by. “It shows us the strange and twisted paths life can take to adapt and survive,” he says.