Among the ocean’s many mysteries is a creature often called the “sea pangolin.” While its name suggests an armored land mammal, this deep-sea inhabitant is a fascinating example of life’s adaptability in extreme environments.
Unmasking the Sea Pangolin
The “sea pangolin” is not a relative of scaly land mammals. It is a deep-sea snail, scientifically known as Chrysomallon squamiferum. It is also called the scaly-foot gastropod or volcano snail.
Its distinctive appearance led to the nickname. The snail’s soft foot is covered in hundreds of overlapping dermal sclerites. These scales give it an armored, plated look, reminiscent of a pangolin’s protective covering.
Life in the Extreme Deep
This unique gastropod makes its home in challenging deep-sea hydrothermal vents. These vents are found primarily in the Indian Ocean, at depths ranging from approximately 2,400 to 2,900 meters (about 1.5 to 1.8 miles) below the surface. The scaly-foot gastropod is known from only three specific vent fields: Longqi, Kairei, and Solitaire.
Life around these vents is characterized by immense pressure, no sunlight, and extremely high temperatures, with water sometimes exceeding 350°C (662°F) as it erupts from “black smoker” chimneys. The water also contains dissolved toxic chemicals, such as hydrogen sulfide. Unlike most life on Earth that relies on photosynthesis, organisms in these deep-sea ecosystems derive their energy through chemosynthesis, a process that uses chemical reactions rather than sunlight.
Biological Marvels
The scaly-foot gastropod thrives in its harsh surroundings. Its shell has three distinct layers, with the outermost layer incorporating iron sulfides, including pyrite, often called “fool’s gold.” This iron-infused armor makes its shell strong and gives it a metallic appearance.
An adaptation for nourishment involves a symbiotic relationship with chemosynthetic bacteria. The snail hosts these bacteria in a specialized, large esophageal gland, about 1,000 times larger than in other snails. These bacteria convert chemicals from the vent fluids into usable nutrients. As a result, adult scaly-foot snails do not eat in the conventional sense, relying entirely on these internal “food factories.”
Other adaptations include a large heart, considered the largest relative to its body size in the animal kingdom. This sizable heart likely aids in circulating oxygen in the low-oxygen conditions of its deep-sea home. The snail is also blind, an adaptation in an environment where no sunlight penetrates.
Facing the Future
The scaly-foot gastropod is classified as endangered by the International Union for Conservation of Nature (IUCN). This designation marks it as the first animal endemic to deep-sea hydrothermal vents to be listed on the IUCN Red List of Threatened Species.
The primary threat to this species is deep-sea mining. There are ongoing investigations into mineral extraction in two of the three known locations where the scaly-foot gastropod resides. These mining activities target valuable minerals found near hydrothermal vents, posing a risk of habitat destruction or severe reduction for this specialized species.