A deep-sea snail shell鈥檚 ability to withstand heavy blows could inspire new generation of body armour.
Crysomallon squamiferum, commonly known as the scaly-foot gastropod, was discovered in 1999 in the Kairei 鈥渂lack smoker鈥� field on the Central Indian Ridge, at a depth of 2420 metres.
at the Massachusetts Institute of Technology and her colleagues studied the snail鈥檚 three-layered shell to find out how it defends itself from crab attacks.
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To assess the shell鈥檚 strength and stiffness, they penetrated it with diamond-tipped probe 鈥� applying the same amount of force that an attacking crab鈥檚 claws might use. They then used the data to model the shell鈥檚 layers and launched a virtual crab attack on it.
Iron hard
It turns out that the snail employs some unique tricks to protect itself. For example, the shell鈥檚 outermost layer consists of strong particles of iron sulphide created in the hydrothermal vents, each around 20聽nanometres across, embedded in a soft organic matrix secreted by the snail. This structure is designed to crack when hit, but in a way that absorbs energy.
Cracks spread only by fanning out around the iron sulphide particles. This 鈥渕icrocracking鈥� not only absorbs energy, it also ensures that larger cracks do not form. What鈥檚 more, the particles of iron sulphide may blunt and deform intruding claws, the study suggests.
A thick, spongy middle layer acts as padding to dissipate further the energy of the blow. This makes it less likely that the mollusc鈥檚 brittle inner shell, which is made of calcium carbonate, will crack.
The middle layer may be an important adaptation to life at a deep-sea hydrothermal vent, suggests Cortiz: the acidic water near black smokers dissolves calcium carbonate and so can quickly enlarge fractures.
The three-layer design could be used to improve body armour 鈥渨ithout the addition of excessive weight鈥�, says Ortiz.
Crack to survive
The idea of coating armour in iron-based nanoparticles that dissipate the energy of a blow by generating microcracks is 鈥渓argely unexplored in synthetic systems鈥� and particularly promising, says Cortiz.
Helmets, motorbikes and Arctic pipelines that collide with icebergs, leading to costly oil spills, could also benefit, says Cortiz, who is also exploring the armour systems deployed by the marine molluscs known as chitons, sea urchins, beetles and a fish known as the Senegal bichir.
鈥淚t is the first step in understanding how we could create an engineered synthetic mimic of a protective structure,鈥� she says.
Journal reference: , DOI: 10.1073/pnas.0912988107
