A golden snail with a foot covered in 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 a knight in armor crawling under the sea,” says Julia Sigwart, a biologist at the Senckenberg Research Institute in Frankfurt and one of the only people to see a live scaly foot snail (Chrysomallon squamiferum)also known as sea pangolin.
The habitat of snails is extreme. They live several kilometers below the ocean’s surface in scorching hydrothermal vents, which are bathed in toxic chemicals and can reach temperatures of over 300C (572F).
The ocean is one of the last truly wild spaces in the world. It’s teeming with fascinating species that sometimes seem to border on the absurd, from fish that look up through transparent heads to golden snails in iron armor. We know more about deep space than we do about the deep oceans, and science is just beginning to scratch the surface of the rich variety of life in the depths.
As mining companies push to industrialize the seafloor and global leaders continue to squabble over how to protect the high seas, a new Guardian Seascape series will feature some of the strangest, wonderful, majestic, ridiculous, hardcore and mind-boggling creatures most recently discovered. They reveal how much there is still to learn about Earth’s lesser-known environment – and how much there is to protect.
The snails’ entire body and lifestyle revolves around bacteria that grow inside a special pouch in their throat, which converts the chemicals coming out of the openings into energy and thus provides all of the snails’ food.
To keep their microbes well fed, scaly-footed snails evolved huge gills to absorb oxygen and chemicals from seawater and then distribute them through the bloodstream and an extremely spacious heart. A human heart of equivalent proportions would be the size of our heads.
When you say that a species is threatened with extinction, everyone understands that
Julia Sigwart, biologist
In 2019, scientists discovered that the scales on snails’ feet are not meant to protect against predatory attacks, but to ward off a toxic threat that comes from within. Bacteria lurking 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 pellets that kill slugs and snails).
The internal structure of their scales acts as tiny exhaust pipes, pulling dangerous sulfur out of the snails’ soft tissues and depositing it as a harmless iron-based compound on the outside.
While they evolved many strange adaptations to survive in vents, scaly-footed snails didn’t count on humans showing interest in their habitat. All three places where they live – an area of less than 0.025 km2 (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 are after the gold, silver and other precious or rare metals deposited on the rocky walls of the smoker’s black chimneys. If their small areas of habitat are damaged or destroyed, scaly-footed snails will 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 a threatened species.
“It’s an incredibly powerful communication tool,” she says. “When you say a species is threatened with extinction, everyone in the world understands that.”
The scaly-footed snail was the first species in the world to be listed as endangered because of deep-sea mining, but there are now many deep-sea molluscs that experts have evaluated and added to the global endangered list.
Related: Deep sea mining could drive hundreds of species to extinction, warn researchers
Of the 184 endemic species that live only in vents, from giant clams to a downy snail by the name of Joe Strummer of the Clash, only 25 are not considered endangered.
These species remain relatively safe, explains Sigwart, because they live in ventilation fields where there is an explicit ban on any future development of offshore mining. This includes marine protected areas in Canadian territorial waters and around the Azores.
Most other species live in offshore hydrothermal vents, which are beyond territorial limits and therefore less protected and more open to mining.
“These are the red list ratings that reflect the status and risk for the entire species and its potential to actually go extinct and completely lose it,” says Sigwart, “and nobody wants that.”
For Sigwart, these unusual clams brilliantly illustrate how evolution is just about being good enough to survive. “It shows us the strange and tortuous paths life can take to adapt and survive,” she says.