Function of colours
 
column spacer Function of colours
  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.
 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of coral-gorgonians taken from a video "We've noted often during the virtual dive the bright coloration of coral-reef fishes, but I wonder what role coloration could play in the lives of coral-reef invertebrates." - Turneffe Island 2002. Video courtesy Andy Stockbridge, Belize.
 
 
REVIEW: before we start on functions of coloration in reef animals, let's take a moment to review a list of possible functions. Most entries in the selection below are fairly obvious, others less so, and a few are dubious. As an exercise, mentally sort them into 2 categories of KNOWN, LIKELY, OR COMMON FUNCTION, and UNKNOWN, UNLIKELY, OR UNCOMMON FUNCTION, then CLICK HERE to see them sorted in a way compatible with what is presented in BCCR. Keep in mind that some entries are controversial, most are untested, and there is some overlap. Note too that many are considered in other parts of BCCR. Ideas from Marshall et al. 2003 Copeia (3): 455. drawing of boxes for quiz on functions of colours

pattern disruption
sighting by predators made easy
camouflage
non-functional metabolic byproduct
induce confusion

warning coloration
species recognition
mating display
attack misdirection

territorial communication
temperature regulation
mimicry
countershading
distinguishing sex
 
 

Function of colours

  Functions of colours and colour patterns in reef animals fall into 2 broad categories of SOCIAL and DEFENSE, one topic of the former, species recognition, being considered here. Two other "SOCIAL" topics, that of TERRITORIAL COMMUNICATION and MATING DISPLAY, can be found in their own section. 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 as a broad summary. A third category of OTHER: UV PROTECTION is also included in its own, short section. CLICK ON a topic to learn about it.
 
 
 

Function of colours: social: species recognition

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of an arrow crab in a crevice taken from a video

"What a gaudy little fellow. It's an arrow crab hunting for food. Perhaps its bright colours are for species recognition. Or maybe it just wants to keep track of where its claws are!" - Turneffe Island 2002. Video courtesy Andy Stockbridge, Belize.

NOTE Stenorhynchus seticornis

 
 

photograph of a queen angelfish Holacanthus ciliaris
There is no mistaking the brilliant colour-demarcations of queen angelfishes, but if these colours function solely for recognition of one member of the species by another, it seems like overkill.

 

 

 

 

Queen angelfish Holacanthus ciliaris 0.25X

 

shoal of French gruntsIn schooling or shoaling species, bright colours may be important in enabling the members to stay together.shoal of sergeant-majors

Shoal of French grunts Haemulon flavolineatum 0.15X. Note in this
photo and the one of the queen angelfish
above the presence of black, blue, and yellow colors. These transmit well through seawater, and have commonly evolved in Caribbean reef fishes

Shoal of sergeant-majors
Abudefduf saxatilis
0.2X

 

 

photograph of a spotfin butterflyfish Chaetodon ocellatus
Distinctive markings near the tail in aggregating species or in pair-bonding species photograph of a pair of 4-eye butterflyfishs Chaetodon capistratusmay enable the trailing member of a pair or group to maintain visual contact.
Kelly & Hourigan 1983 Anim Behav 31: 615.

Like most butterflyfish species,
the spotfin Chaetodon ocellatus
tends to travel in pairs 0.4X

Do the false eyespots on 4-eye butterflyfishes Chaetodon capistratus function as an aid in pair-travelling as well as for misdirecting attacks by predators to the tail region? 0.4X

 
photographs of eye coloration in various reef fishes with respect to consideration of functionEyes in many reef fishes are conspicuously highlighted, and may act as possible recognition cues for conspecifics.
 

photograph of a 3-spot damselfish Stegastes planifrons
Different adult and juvenile colorations in a species may allow the 2 life stages to coexist because the adult does not associate the juvenile coloration with a possible competitive threat for food and space.

NOTE lit. "live together". In ecology it has the meaning of living together without competition driving one of the participants away
photograph of a juvenile 3-spot damselfish Stegastes planifrons
The 3-spot damselfish Stegastes planifrons is just one of many
examples of reef-fishes where adults (Left) and juveniles (Right) are distinctively coloured 1X





0.25X

  So far, this part of how colours function in species recognition has dealt with intraspecific recognition; that is, recognition of one member of a species by another. However, what about interspecific recognition, but not simply instances of a predator identifying a prey or a territorial encounter?
For example, cleaner fishes require that they be easily located and recognised by their client fishes from a distance, and this suggests that "stand-out" or "poster" colours, ones that transmit well through seawater and are easy to see, would be advantageous. The cleaner-fish species featured below have yellow combined with blue and black, combinations that transmit well through seawater. Thresher 1977 Z Tierpsychol 43: 152.
 
photograph of cleaner gobies Gobiosoma sp.
photograph of a juvenile French angelfish
photograph of a juvenile hogfish Bodianus rufus
Cleaner gobies Gobiosoma sp. 0,75X Juvenile French angelfish Pomacanthus paru are cleaners and have their own cleaning stations 0.5X Brightly coloured juvenile spotfin hogfish Bodianus pulchellus cleans a willing sergeant-major 0.33X
 

photographs of various cleaner shrimps to show their coloration
Are cleaner shrimps as easy to see by their clients as cleaner fishes? Their colours, although quite noticeable to our eye, nonetheless seem more muted than those of cleaner fishes. Note the variegated colours of red, blue, mauve, purple, and white. Except for the brilliant blue of the Pederson shrimp that is notably a "stand-out" or "poster" colour in the clear waters of the reef, colours of the other species, especially shades of red, will not transmit well through seawater. In fact, against some backgrounds they almost seem to camouflage the shrimps.

 

 
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