Secret Signal: Fish allurement that predators don’t see

In a rare demonstration of secret messaging in animals, a swordtail fish uses ultraviolet (UV) wavelengths as a private courtship channel, biologists now report.

SWORDED AFFAIRS. Male swordtails trail their exaggerated tails. Ryan/G. Rosenthal
Picture above shows the bright horizontal stripes, in the ultraviolet spectrum, that entice females.