The "Hyper-Visible World" hypothesis for the dazzling colours of coral reef fish.

No evolutionary explanation for the striking colouration of coral reef fish has been established to date. Here I present the "Hyper-Visible World" hypothesis, which proposes that coral reef habitats impose special conditions on the evolution of body-colour communication for mobile fish - that is, fish that roam across coral reef formations. The special conditions are: 1) the high clarity of water during daylight hours, and 2) the unpredictable pattern/ visual complexity of the coral habitat itself. The hypothesis suggests that, in a signal transmission framework, the visual exposure (signal) of mobile fish cannot be effectively reduced so as to make a difference to predator-prey interactions. This negates the possibility of effective colour-based camouflage. In contrast, the selective pressures that usually come secondary to camouflage (such as sexual, aposematic or territorial display) benefit from these same conditions, driving the evolution of the colour patterns in this environment - the conspicuousness and dazzling colour diversity that we commonly associate with coral reef fish.