Iron-plated Snail

This post contributed by Nadine Lymn, ESA Director of Public Affairs

 Another example of the ingenuity of nature: researchers are finding inspiration in the extraordinarily strong exoskeleton of a deep-sea snail, Crysomallon squamiferum.  The mollusk’s iron-plated shell is giving researchers insights that could lead to stronger materials for airplane hulls, cars, and military equipment.

Researchers at the National Science Foundation (NSF)-supported Materials Research Science and Engineering Center at the Massachusetts Institute of Technology (MIT) write about the snail’s iron-plated protection in the January 19 issue of the Proceedings of the National Academy of Sciences.

Also called the “scaly-foot gastropod”, Crysomallon squamiferum was discovered back in 1999, over two miles below the central Indian Ocean, deep within hydrothermal vent fields.  Fluids in these vents are high in sulfides and metals, which the snail incorporates into its shell.  The gastropod’s shell has three layers: a highly calcified inner layer, a thick organic middle layer, and an outer layer that is fused with granular iron sulfide.  It is unlike any other known natural or synthetically engineered armor.

MIT project leader Christine Ortiz and her colleagues have been testing the shell’s properties, simulating predatory attacks with computer models as well as with “indentation testing”—striking the top of shells with a sharp probe to measure the hardness and stiffness of the shell.

In a NSF press release Ortiz says:

Our study suggests that the scaly-foot gastropod undergoes very different deformation and protection mechanisms compared to other gastropods.  It is very efficient in protection, more so than the typical mollusk.

Potential predators that are found in the same regions as C. squamiferum include the cone snail, which penetrates its prey with a harpoon-like tooth before paralyzing it with venom, and sea-faring crabs, which use their claws to squeeze for days until the mollusk’s shell gives way. 

The researchers write in the PNAS report that C. squamiferum’s impressive exoskeleton is:

…..advantageous for penetration resistance, energy dissipation, mitigation of fracture and crack arrest, reduction of back deflections, and resistance to bending and tensile loads.

Another vivid example of the evolutionary race between prey and predator which in this case also holds promise for better protective materials for humans.

Photo credit: Dr. Anders Warén, Swedish Museum of Natural History, Stockholm, Sweden.

Yao, H., Dao, M., Imholt, T., Huang, J., Wheeler, K., Bonilla, A., Suresh, S., & Ortiz, C. (2010). Protection mechanisms of the iron-plated armor of a deep-sea hydrothermal vent gastropod Proceedings of the National Academy of Sciences, 107 (3), 987-992 DOI: 10.1073/pnas.0912988107