To see off piranha this fish has strong armour

FISH SCALES have to be tough, to provide protection, flexible, to permit movement and light, to preserve buoyancy. These conflicting requirements have driven the evolution of scales that can endure considerable punishment without impinging on mobility. But work just published in , by Robert Ritchie and Marc Meyers of the University of California’s campuses at Berkeley and San Diego respectively, suggests that one fish, the pirarucu, has taken things to extremes. The reason is that pirarucu share their habitat with piranha.Pirarucu can be 4.5 metres long and may weigh 200kg. That makes them one of the world’s largest freshwater fish. The places they call home are often lakes cut off from river channels in the Amazon basin. Just the sort of habitat favoured by piranha.