Coloration of reef organisms
 
 

tabulated information on function of colours in coral-reef organisms
Here is the sorting done in accordance with how the functions are dealt with in BCCR:

The "known" functions are fairly straightforward, and each is considered in BCCR.

As for the "unknown" functions, colours as non-functional metabolic byproducts are unlikely to have been selected for in evolution. Although common among terrestrial vertebrates, colours for distinguishing sex only occur in a few species such as parrotfishes and wrasses where sex change later in life leads to a dominant, terminal-male that is distinctly coloured from the harem females. In all other reef fishes and invertebrates, sexes are visually indistinguishable. Colour for temperature regulation is inapplicable, as most reef fishes and all invertebrates are ectothermic, that is, their internal temperatures are the same as the surrounding seawater. Exceptions to this may be large sharks and some large fishes where organ temperatures deep in the body may be warmer than the surrounding seawater, but this is simply a product of metabolism and is not actively regulated. As for sighting by predators made easy, well, you can judge that for yourself.

 
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