Coloration in reef organisms
column spacer Coloration in reef organisms
  hot buttons for colours section of Biology of Caribbean Coral Reefs website
This section deals with the function of colours. Topics of HOW COLOURS ARE CREATED and HOW COLOURS ARE PERCEIVED can be accessed via the icons.

Function of colours

  Functions of colours and colour patterns in reef animals mainly fall into two categories of SOCIAL and DEFENSE, one topic of the former, territorial communication, being considered here. Other social and defense topics can be found in their own sections. Most or all of these topics have been mentioned elsewhere in the BCCR but, by its nature, this section on FUNCTION OF COLOURS pulls them together in broad summary. A third category of OTHER: UV PROTECTION also has its own, short section. CLICK ON a topic to learn about it.

Function of colours: social: territorial communication

seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of parrotfish taken from a video

"Terminal-phase male parrotfishes are so much brighter than the initial-phase female. For example, compare the terminal-phase male stoplight with the initial-phase one. Could this be to communicate his worth as a mating partner to females? Or perhaps it just makes him stand out in territorial confrontations with other males. " - Little Cayman 2002.

NOTE Sparisoma viride


photograph of a terminal-phase stoplight parrotfish Sparisoma viride
Terminal-phase males of protogynous species such as parrotfishes and wrasses establish and police territories that include the home ranges of several reproductively mature females. Other sexually mature males, but lacking the terminal-phase coloration, are bossed out of the area.

NOTE lit. "first female", referring to a species that changes sex from female to male during its life cycle. For more information on this subject refer to COMPETITION: MOTILE ORGANISMS: SPACE/TERRITORY COMPETITION


Bright coloration of a terminal-phase (male) stoplight
parrotfish Sparisoma viride is thought to allow easy
recognition of one territory holder by other adjacent
territory holders and by invading males looking
to set up their own territories...and harems 0.3X

seahorse dive leader for Biology of Caribbean Coral Reefs Website photograph of a stoplight parrotfish being cleaned taken from a video

Bright colours in territorial males helps in maintaining harems and forcing out other males, but one wonders, as in this terminal-male stoplight parrotfish, if there is risk of attracting the attention of their own predators. - Little Cayman 2002

NOTE Sparisoma viride


photograph of several bluehead wrasses Thalassoma bifasciata showing all life stages
Initial-phase bluehead wrasses are yellow in colour and are mostly female. If the current terminal-phase dominant male is eaten by a predator or otherwise disappears, a new one develops, mostly from a female, but sometimes from a male. The transformation begins within a short time after disappearance of the male, takes a few days to complete, and is irreversible.




Mixed life-stages of bluehead wrasses Thalassoma bifasciatum,
including several juveniles and initial-phases with all-yellow bodies,
2 terminal-phase males with blue and green bodies, and one transitional-phase
(changing from female to male) with a blue head and tail, and yellow body 0.8X


photograph of mixed phases of bluehead wrasses Thalassoma bifasciatum
The blue-green colours of terminal-phase male bluehead wrasses transmit well through tropical seawater and presumably help the competing territorial bosses to see one another. Border disputes between the males are mainly ritualistic, involving mock attacks and mouth-gaping.




Two terminal-phase male bluehead wrasses Thalassoma
are just blurs as they swim around several
initial-phase, likely harem-female, individuals 0.7X


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