Chrysomallon squamiferum

Geographic Range

Volcano Snails (Chrysomallon squamiferum) live in 3 different deep-sea hydrothermal vent fields, all located in the Indian Ocean off the Eastern and Southern coasts of Madagascar. Originally found in the Kairei vent field, and later found in the Solitaire and Longqi vent fields. The Longqi vent field is located 2,300 km southwest of the Kairei vent field, and the Kairei field is 700 km south of the Solitaire field. (Chen, et al., 2015a)

  • Biogeographic Regions
  • indian ocean


Volcano Snails inhabit 3 different hydrothermal vent fields located in the Indian Ocean. They are found in the Kairei, Solitaire, and Longqi vent fields, 2,400 to 2,900 meters deep near black-smoker chimneys that emit minerals. The deep sea vents can heat up to over 400 degrees celsius or 700 degrees Fahrenheit, but the water does not boil due to the ~250 atm or 3,670 psi of pressure. (Chen, et al., 2015b; National Oceanic and Atmospheric Administration, 2023; Woods Hole Oceanographic Institution, 2023)

  • Range depth
    2400 to 2900 m
    7874.02 to 9514.44 ft
  • Average depth
    2600 m
    8530.18 ft

Physical Description

Volcano Snails have shells that swirl inwards 2-3 times, and sclerites that surround the snail's foot, giving them the nickname "scaly-foot gastropod". The snails have two cephalic tentacles and no eyes.

Younger snails have both a smaller shell size and smaller sclerites. Young volcano snails have a few rows of sclerites, whereas adults have many sclerites in an asymmetrical fashion.

Each of the groups of snails in the three different vent fields has a different shell and sclerite color because the smokers emit slightly different chemicals. Those that live in the Solitaire vent field have a white color due to lack of iron, while those in the Kairei vent field have a black color and are also magnetic because of the greigite presence. Those located in the Longqi vent field have a brown-golden color due to the presence of both pyrite and greigite. (Chen, et al., 2015c; Chen, et al., 2015a; Crew, 2021; Micu, 2021)

  • Sexual Dimorphism
  • sexes alike
  • Range length
    5 to 45 mm
    0.20 to 1.77 in
  • Average length
    32 mm
    1.26 in


Due to the lack of research on the life cycle and the reproductive cycle, there is also a lack of knowledge on the growth of volcano snails. Scientists do know that juvenile snails do not have mature gonads, and adults have varying levels of gonad maturity. Juvenile snails also have smaller shell sizes than adults. (Chen, et al., 2015b)


Since volcano snails are simultaneous hermaphrodites, and they self-fertilize, they have no competition and no specific mating behaviors. (Chen, et al., 2015b; "Scaly-Foot Snails; Chrysomallon Squamiferum", 2023)

Volcano snails are simultaneous hermaphrodites, meaning each individual has the ability to produce both egg and sperm cells, and self-fertilizes. Spermatophores are produced and are likely the method of internal fertilization. Little research has been done on these snails' reproductive process due to their extreme habitat. (Chen, et al., 2015b; "Scaly-Foot Snails; Chrysomallon Squamiferum", 2023)

There is no current research on the parental investment of volcano snails.


There is little to nothing known about the lifespan of volcano snails. There was an instance of the species being kept alive for over 3 weeks in captivity at atmospheric pressure. (Japan Agency for Marine-Earth Science and Technology, 2009)


There is little known about the behavior of the volcano snails, but they are assumed to be sedentary and solitary due to the simplicity of their digestive system and not needing a mate for reproduction. (Chen, et al., 2015b)

Home Range

Due to limited information about behavior, the home range of volcano snails is unknown.

Communication and Perception

Research on the interactions of volcano snails with others and the environment is very limited, however, scientists do know that they have no eyes or optic nerves. There are nerves in the cephalic tentacles, as well as in the mantle and foot muscles. (Chen, et al., 2015b)

Food Habits

Volcano snails are obligate symbiotrophs, meaning they need a symbiotic relationship to survive. They have a larger oesophageal gland that houses chemosynthetic bacteria, that provide energy to the snails. Scientists also found pellets in the hindgut which are thought to be sulfur made by the endosymbionts and allow for detoxing the hydrogen sulfide. (Chen, et al., 2015b; Goffredi, 2010; "Scaly-Foot Snails; Chrysomallon Squamiferum", 2023)

  • Other Foods
  • microbes


Volcano snails have their sclerites and protected shells to protect themselves from predators like the genus Phymorhynchus. They inject venom into their prey, so the volcano snail's protection prevents these attacks. (Warén, et al., 2003)

Ecosystem Roles

Volcano snails act as prey to predatory gastropods like the Phymorhynchus genus. Since they have endosymbiotic bacteria in their oesophageal gland, they do not need to hunt and therefore are not predators. (Warén, et al., 2003)

Mutualist Species
  • No direct species named; described as thioautotrophic gammaproteobacteria

Economic Importance for Humans: Positive

The main importance of volcano snails is knowledge. Their ability to make their own armor out of the minerals surrounding them has never been seen before, so anything that can be learned is important.

  • Positive Impacts
  • research and education

Economic Importance for Humans: Negative

There is no known adverse effect of volcano snails on humans.

Conservation Status

Volcano snails are labeled as endangered. It is the first species to be named endangered due to deep sea mining. Two of the three known seabeds they inhabit have mining licenses, and none are protected from deep-sea mining. (Sigwart, 2017; Sigwart, 2019; Sigwart, et al., 2019a; Sigwart, et al., 2019b)

Other Comments

Other common names for volcano snails are the scaly-foot gastropod, sea pangolin, or scaly-foot snail. It did not have a scientific name until 2015, despite its discovery in 2001. (Chen, et al., 2015a)


autumn ryann (author), Colorado State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.



union of egg and spermatozoan

internal fertilization

fertilization takes place within the female's body

native range

the area in which the animal is naturally found, the region in which it is endemic.

oceanic vent

Areas of the deep sea floor where continental plates are being pushed apart. Oceanic vents are places where hot sulfur-rich water is released from the ocean floor. An aquatic biome.


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.


remains in the same area


lives alone


uses touch to communicate


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


2023. "Scaly-Foot Snails; Chrysomallon Squamiferum" (On-line). Marine Bio. Accessed February 10, 2023 at

Chen, C., J. Copley, K. Linse, A. Rogers, J. Sigwart. 2015. How the mollusc got its scales: convergent evolution of the molluscan scleritome. Biological Journal of the Linnean Society, Volume 114, Issue 4: 949-954. Accessed February 10, 2023 at

Chen, C., J. Copley, K. Linse, A. Rogers, J. Sigwart. 2015. The heart of a dragon: 3D anatomical reconstruction of the ‘scaly-foot gastropod’ (Mollusca: Gastropoda: Neomphalina) reveals its extraordinary circulatory system. Frontiers in Zoology, Volume 12, Issue 13: 1-16. Accessed February 10, 2023 at

Chen, C., K. Linse, J. Copley, A. Rogers. 2015. The ‘scaly-foot gastropod’: a new genus and species of hydrothermal vent-endemic gastropod (Neomphalina: Peltospiridae) from the Indian Ocean. Journal of Molluscan Studies, Volume 81, Issue 3: 322-334. Accessed February 10, 2023 at

Crew, B. 2021. "The scaly-foot snail’s shell is made of actual iron – and it’s magnetic" (On-line). Australian Geographic. Accessed February 18, 2023 at

Goffredi, S. 2010. Indigenous ectosymbiotic bacteria associated with diverse hydrothermal vent invertebrates. Applied Microbiology International, Volume 2, Issue 4: 479-488. Accessed February 10, 2023 at

Japan Agency for Marine-Earth Science and Technology, 2009. "Extensive population of a “rare” scaly-foot gastropod discovered" (On-line). Accessed February 25, 2023 at

Micu, A. 2021. "The Iron Snail lives on volcanic vents, two miles under the sea, all thanks to its spectacular armor" (On-line). ZME Science. Accessed February 18, 2023 at

National Oceanic and Atmospheric Administration, 2023. "What is a hydrothermal vent?" (On-line). NOAA. Accessed February 18, 2023 at,reemerges%20to%20form%20the%20vents.

Sigwart, J., C. Chen, E. Thomas. 2019. "Scaly-Foot Snail" (On-line). IUCN Red List. Accessed February 10, 2023 at

Sigwart, J. 2017. "Deep-sea conservation and the ‘scaly-foot gastropod’" (On-line). The Newsletter of the IUCN/SSC Mollusc Specialist Group. Accessed February 10, 2023 at

Sigwart, J. 2019. "Sea Pangolin: the first ever species endangered by potential deep sea mining" (On-line). The Conversation. Accessed February 10, 2023 at

Sigwart, J., C. Chen, E. Thomas, L. A, M. Böhm, M. Seddon. 2019. Red Listing can protect deep-sea biodiversity. Nature Ecology and Evolution, Volume 3: 1134. Accessed February 10, 2023 at

Warén, A., S. Bengtson, S. Goffredi, C. Van Dover. 2003. "A Hot-Vent Gastropod with Iron Sulfide Dermal Sclerites" (On-line pdf). Science. Accessed February 10, 2023 at

Woods Hole Oceanographic Institution, 2023. "Hydrothermal Vent Boiling Points" (On-line). Dive and Discover. Accessed February 18, 2023 at,A%20hydrothermal%20vent%202%2C500%20meters%20deep%20experiences%20250%20atmospheres,3%2C672.5%20pounds%20per%20square%20inch.