A school of fish might seem like a sea of identical faces, but at least one species has no problem telling its comrades—and even strangers—apart, new research says.                                                                                                

To human eyes, which cannot see ultraviolet light, the Ambon damselfish (Pomacentrus amboinensis), appears yellow with a few spots.

But to damselfish, which can see ultraviolet wavelengths, their fellow species sport a complex array of facial patterns that are unique to each individual.

"The idea is that these patterns help the fish communicate secretly—without attracting the attention of predators, which, like us, are UV blind," says experiment leader Ulrike Siebeck of the University of Queensland, Australia. (See photo gallery: "Masters of Undersea Camouflage.")

Scientists could see these patterns when they viewed the