Volcano Snail

The volcano snail lives comfortably in temperatures of up to 750 degrees Fahrenheit.

Facts

• The volcano snail is the only animal on earth whose body is made up of mineralized iron.
• You can pick up a volcano snail with a magnet.
• The volcano snail can withstand temperatures of up to 750 degrees Fahrenheit.
• The volcano snail could go extinct if conservation efforts are not made for it with the onset of seabed mining and exploration. Its habitats are on the verge of being destroyed by human activity.
• Volcano snails don’t have to eat. They have a symbiotic relationship with bacteria that live in their esophageal gland. These bacteria produce energy for them.
• The volcano snail lives in deep-sea hydrothermal vents 1.5 to 1.8 miles below sea level. The atmospheric pressure here is crushingly low, but the snails have adapted to it.
• Volcano snails have under-developed digestive systems, which is why they do not need to eat. Their radula is weak, and they have very a simple digestive tract.
• The esophageal gland of volcano snails is a thousand times larger than in other snail species. This is to house the endosymbiotic bacteria that supplies their nutritional needs.
• The volcano snail has hundreds of pieces of iron attached to its foot called sclerites. Their actual function is unknown.
• The heart of the volcanic snail makes up 4% of its entire body volume. This is a very high proportion for any animal. The reason for their having such a big heart is believed to be efficient oxygen production for the endosymbiotic bacteria.
• Volcano snails do not have eyes or tentacles.
• The shell of the volcanic snail is made up of three layers. The middle layer is organic, proteinous, and very tough. It is so tough that scientists are bent on figuring out how to use its features to create military-grade protective gear from it.

Summary

The volcano snail is one of the most unconventional snail species and animals in the world. They live in shells made of iron, they have iron bits on their feet, and they don’t need to eat. These scaly-foot snails live in extreme conditions of heat and pressure. They can be considered living relics, since their awe-inspiring features used to be pretty common…half a billion years ago.

Scientific Name

The volcano snail is classified as Chrysomallon squamiferum. Chrysomallon comes from Ancient Greek and means “golden-haired” after the golden color of one of the iron sulfide compounds, pyrite, which is located in the shell of the snail. The specific name, squamiferum, is from Latin and means “bearing scales,” alluding to the iron pieces on the foot of the snail called sclerites.

Volcano snails are deep-sea snails which inhabit the hydrothermal vents miles below sea level. These vents spew scalding hot mineral water and the volcano snails have adapted to the extreme conditions of this environment by encasing themselves in iron.

Volcano snails are also commonly known as sea pangolins, scaly-foot gastropods, and scaly-foot snails. They belong to the family Peltospiridae which is a very small family of gastropods that contains no subfamilies. The snails also belong to the order of deep-sea snails, Neomphalida. Neomphalida contains only one superfamily called Neomphaloid.

Evolution and History

The volcano snail’s hydrothermal habitat influenced some of its physical and dietary evolutionary traits over millions of years. Mineralized iron and sulfur infuse the shells and bodies of these snails. However, while volcano snails are the only animals on earth who have this incredible feature, it was a pretty common physical trait in the Cambrian Epoch 540 million years ago.

Volcano snails are able to withstand harsh temperatures of 750 degrees Fahrenheit and extremely low pressure due to their iron-clad armor.

Studies of the volcano snail’s genes reveal that the genes which control its scaly foot and shell actually did not evolve much in the last 540 million years. That means that the genes are much older than this.

The volcano snails also developed large hearts which make up 4% of its body volume, an unusually large proportion. This is to provide enough oxygen for the endosymbiotic bacteria that live in its stomach and provide for its nutritional and energy needs.

The sea pangolin comes from the gastropod family Peltospiridae whose first recorded appearance in history occurred in the Eocene Period 47.8 million to 41.3 million years ago.

Appearance

The volcano snail has one of the most unique and bizarre bodies in the animal kingdom. It is the only animal species whose body is made of mineralized iron. Because this snail lives in hydrothermal vents miles deep in the ocean, it is subject to intense atmospheric pressure and intense heat of up to 750 degrees Fahrenheit. It has adapted to these conditions by forming a body that can withstand and protect it.

Their Shell

The shell of the sea pangolin consists of three layers: the outer layer, middle layer, and inner layer.

The outer layer of the volcano snail’s shell is made of iron sulfides and is the only animal whose skeleton possesses this substance. The outer shell is 30 nanometers thick and black.

The middle layer of the shell is the periostracum or the waterproof organic layer of “skin” found in gastropods. It is thick, brown, and made of a variety of proteins which are conchin. This middle layer of the snail’s shell is tough and protects the body against physical stress and tension such as a predator attack. It also serves to disperse excess heat.

The inner layer of the shell is creamy white in color due to the presence of aragonite, a type of calcium carbonate. The shell of the sea pangolin has three whorls and the shell opening is elliptical.

Their Foot

The snail foot is one of the most characteristic features of the volcano snail. Hundreds of iron sclerites reinforce its sides that measure about one to five millimeters each. These sclerites are hard, calcified pieces of mineralized iron with soft tissue at each one’s core. The outermost layer of the sclerite is made of iron pyrite and greigite, sulfides. The sclerites give the snail’s foot a scaly appearance, hence its nickname “scaly-foot gastropod.” The function of the sclerites are currently unknown. The body of the volcano snail is red in color.

Their Internal Organs

The volcano snail’s internal organs differ from a lot of snail and animal species as well. It has a really big heart, and we don’t mean its kindness. Its heart makes up about 4% of its body volume which is large for any animal. To compare, the human heart is only 0.3% of our body volume.

The digestive system of the sea pangolin is simple and lacks development that zoologists believe that it doesn’t eat, so it depends on endosymbiotic bacteria to produce energy for it. The snail has an esophageal gland where these bacteria reside. It also has a stomach, a reduced intestine, and an anus just above the genital opening.

The volcano snail does not have eyes or tentacles.

Behavior

There is little to almost no information about the behavior and habits of the volcano snail due mostly to the harshness of its environments.

The scaly-foot gastropod lives at hydrothermal vents in the Indian Ocean. Here, they interact with other often venomous snail species and crabs as well who prey on the volcanic snail.

It is unclear whether or not the snails live a solitary life, but it is possible, especially considering the fact that they are hermaphrodites. They do not need to mate with other snails to reproduce.

Volcano snails also live a sedentary lifestyle. Because they partner with endosymbiotic bacteria to cater for their nutritional needs, they do not need to hunt for prey. Their digestive system is poorly developed anyway, so they are not active creatures.

Diet

A fun fact about volcano snails is that they do not need to eat food to survive. While this may sound impossible, it is perfectly normal life for the snail. The volcano snail is an obligate symbiotroph.

After their larval stage, they get all of their nourishment not from feeding, but from endosymbiotic bacteria. These bacteria make their own food through a process called chemoautotrophy, or chemosynthesis.

The volcano snail has an esophageal gland that houses the endosymbiotic bacteria. This gland is about a thousand times bigger than it is in other snails to properly lodge the bacteria. It also has a stomach containing pellets, likely sulfur granules made by the bacteria to detoxify hydrogen sulfide.

Habitat and Population

Volcano snails are endemic to Africa, particularly, the island of Mauritius in the Indian Ocean. This snail boasts of hydrothermal vent origins and resides in the deep ocean ridges.

The range of the volcano snail has a limit. It occupies the hydrothermal vents deep in the Indian Ocean. The snail is at depths of 1.5 to 1.8 miles below sea level at severe atmospheric pressure. To put this into perspective, humans can only survive at about 22 miles underwater before our bones crush under the pressure.

Volcano snails inhabit three recorded locations: the Longqi vent field, the Kairei vent field, and the Solitaire vent field. The main difference between these three vent fields is the level of iron concentration. Due to the inaccessibility of these locations, there is difficulty in obtaining information about the volcano snails who live in these regions. However, the Chrysomallon squamiferum population at the Longqi vent field is reportedly teeming.

Nevertheless, the volcano snail is an endangered species according to the IUCN Red List of Threatened Species. Its habitat is under threat due to human activities of deep-sea mining and exploration.

Reproduction and Lifespan

Like many other snail species, the volcano snail is simultaneously hermaphroditic. This means that it has both male and female sexual reproductive organs present at the same time. It is the only species in the family Peltospiridae to be a simultaneous hermaphrodite. Volcano snails practice self-fertilization.

Volcano snails lay eggs that do not depend on the mother for nutrients, and solely rely on a yolk sac for nourishment. Their eggs are also negatively buoyant, meaning that they are heavier than water.

Volcano snails might have a larval or planktonic stage of life after the eggs hatch, but this is under speculation. Because of the volcano snail’s rarity and also its tight range, it is not easy to be studied. The intricate details of its reproductive life cycle are still under research.

The lifespan of the volcano snail is unknown, but sea snails typically survive for up to ten years or even more in the wild. Volcano snails do not do well in aquarium environments and only survived over three weeks in one.

Predators and Threats

Because of their deep-sea hydrothermal habitat, the scaly-foot gastropod does not have many natural predators. However, it does have a couple of known predators: other venomous snails and crabs that inhabit the area. The volcano snail’s shell seemingly protects it from attacks, but it can still be hurt or die by the assailants. These animals not only prey on the volcano snail, but also compete with it for living space.

The main threat volcano snails face is habitat loss due to seabed mining. Currently, two of the three locations where the snail inhabits have the go-ahead to start the mining exploration process, namely, the Longqi and Kairei vent fields. Seabed mining disrupts the ecosystem and the temperatures of the vent fields which the volcano snails have an adaptation to. No conservation efforts are in place to secure the future of the scaly-foot gastropod.

Read Next

• Discovered in the Deep: The Snail with Iron Armor
• 5 Incredible Deep Sea Creatures Seem Straight From Science Fiction
• 10 Deep Sea Creatures: Discover the Rarest Scariest Animals Beneath the Seas!

1. , Available here: https://www.nature.com/articles/s41467-020-15522-3
2. , Available here: https://www.marinebio.org/species/scaly-foot-snails/chrysomallon-squamiferum/
3. , Available here: https://en.wikipedia.org/wiki/Scaly-foot_gastropod
4. , Available here: https://pubmed.ncbi.nlm.nih.gov/33319911/