Fish scales may point to armour of the future

Scales that protect a quarrelsome fish from the bites of its own fellows as well as from predators may hold the key to the armour of the future, U.S. researchers reported on Sunday.

The light, multilayered design of its scales has helped Polypterus senegalus survive for 96 million years, the team at the Massachusetts Institute of Technology reports.

Writing in the journal Nature Materials, the MIT team said they had figured out how it works. Each scale is layered so it deflects the pressure of a crunching bite, they said.

Cracks do not travel far - the design forces cracks to run in a circle around the penetration site, rather than spreading through the entire scale and leading to catastrophic failure, they said.

"Many of the design principles we describe - durable interfaces and energy-dissipating mechanisms, for instance - may be translatable to human armour systems," MIT's Christine Ortiz, who led the study, said in a statement.

With funding from the U.S. Army, Ortiz and colleagues carefully studied scales from P. senegalus, which lives at the bottom of freshwater, muddy shallows and estuaries in Africa.

It is noted for its heavy armour.

"The primary predators of P. senegalus are known to be its own species or its carnivorous vertebrate relatives, and biting takes place during territorial fighting and feeding," Ortiz and colleagues wrote in their report.

It evolved the armour millions of years ago, when fearsome predators lurked. "In ancient times, many large invertebrate predators existed. For example, the carnivorous eurypterid was a giant arthropod that possessed biting mouth parts, grasping jaws, claws, spines and a spiked tail," they wrote.