Crabs can produce a bromine-rich biomaterial 1.5 times harder than Perspex "and extremely fracture resistant", said University of Oregon scientists.
According to the University, the material is a new member of a class of structural biomaterials that employ heavy atoms like zinc, iodine and iron.
"It's not yet clear why heavy elements are used," lead researcher Robert Schofield said. "Perhaps the mass of the atoms themselves plays a role in damping vibrations that can lead to fracture."
The translucent substance is found on the claw tips of pachygrapsus cassipes and is also is present on the walking legs of cancer magister.
"The types of crabs that use this trick for their claw tips rely on the tips fitting together like forceps in order to pick and hold bits of food, and fracture damage could make the tips useless," said Schofield. "They include many common crabs such as hermit crabs, which have one large claw for crushing, and a small claw tipped with this biomaterial for finer work."
The material can bend six times further before breaking than the material used in other regions. "If the tip were made of the same material as the rest of the crab, it could never stay sharp and the crab would have difficulty clinging," added Schofield.
These heavy-element biomaterials had escaped notice until now because they are typically employed by small organisms such as insects - which the team developed custom machines and techniques to measure.
"It turns out that fracture tends to be a bigger problem for small organisms than for large ones," Schofield said. "Humans are just starting to try to engineer tiny machines and tools, and we have a lot still to learn from organisms that have coped with being small for millions of years."
