Mandarin dragonet

Photo: Lakshmi Sawitri · CC BY

Mandarin dragonets are among the most colourful fish in the ocean — their skin contains a blue pigment (cyanophycin) produced directly by the fish rather than by chromatophores, a mechanism shared by only one other fish species. They are covered in toxic mucus instead of scales, which protects them from predation and allows their vivid advertisement colouration without camouflage. The evening spawning display, which occurs nightly at consistent sites, is one of the most reliably predictable and visually spectacular courtship events in reef fish.