Coloration of reef organisms
 
column spacer Coloration of reef organsims
  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 icon.
 
 

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 latter, mimicry, being considered here. 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 UV PROTECTION is also included in its own, short section. CLICK ON a topic to learn about it.
 
 
 

Function of colours: defense: mimicry

 

Mimicry is when an animal's shape and colour resemble something else in order to attract its prey, hide from its prey, hide from its predators, or to benefit in copy-cat fashion by appearing to be another animal entirely. Fishes such as frogfishes that use lures to attract their prey are employing mimicry, and colours as well as form and behaviour are involved.

This section of mimicry deals with eyespot mimicry, while other sections deal with FISHING LURES & CAMOUFLAGE MIMICRY, AGGRESSIVE MIMICRY, and BATESIAN & MULLERIAN MIMICRY.

 
 

Function of colours: defense: mimicry: eyespot mimicry

 
 
seahorse dive leader for Biology of Caribbean Coral Reefs website photograph of a 4-eye butterflyfish taken from a video

"I've always liked butterflyfishes. I like their colours, their eyebars, their spousal devotion, their busyness and, in these 4-eyes, I like their eye-mimicking spots. Is this so that predators attack the wrong end, do you think? The spots are larger than real life...perhaps they mimic a much larger individual which the predator would be wise to leave alone." - Cayman Brac 2003

NOTE Chaetodon capistratus

 
 

photograph of a 4-eye butterflyfish Chaetodon capistratus
photograph of a four-eye butterflyfish from aboveMost world species of butterflyfishes have camouflaged eyes and a few have false eyespots, both features demonstrating that eyes are important signals to predators. False eyespots of butterflyfishes may function to misdirect attacks or generally to confuse potential predators. The eyespots are primarily located in areas of the body that would favour survival after attack. Note in the photograph on the Left the blue highlighting around the "pupil" of the fake eye, the contrasting white surrounds, and also the spines erected for defense. If such eyespots truly misdirect predators' attacks, then wouldn't we expect to see relatively more scarring around the butterflyfishes' tail regions?


Four-eye butterflyfish Chaetodon capistratus 0.75X

From above the illusion
is even better 0.5X


 

photograph of a mating pair of four-eye butterflyfishes swimming together
What about alternative ideas for the function of eyespots? We know that most or perhaps all species of butterflyfishes pair-bond as adults, so perhaps ideas relating to this aspect of their behaviour can be generated. Think about what these might be, then CLICK HERE for examples of ideas.

 

 

A possible mating pair of four-eye butterflyfishes
Chaetodon capistratus swimming together 0.25X

 

photograph of an adult rock beauty Holocanthus tricolour
But how do we explain "eyespots" in the juvenile stage of a reef-fish species, but not in the adult? Are we to believe that the spots act in defense of the juvenile, but are not "required" in the adult? The answer is yes, as we have to believe the "eye-spotless" adult colours must be serving another, presumably more important, function. Let's look at another Caribbean reef-fish species as an example, the rock beauty Holacanthus tricolor.drawing of a juvenile rock beauty Holocanthus tricolor

As a juvenile, the rock beauty has eyespots, but not as
an adult 1.5X. Note that the blue and yellow colours are
ones that transmit well through tropical seawater

 

The adult rock beauty is eye-spotless, but maintains the black,
yellow, and blue colours of the juvenile, the last two being
colours that are most visible in the clear waters of the reef
Is it possible that the colours serve both a defensive function
in the juvenile and a social function in the adult? 0.4X

 

photograph of an ocellate swimming crab showing eyespots
The ocellate swimming crab Achelous (Portunus) sebae inhabits shallow back-reef area in sand and rubble areas. Its defenses are swimming, and claws that are sharp and lightning fast. If these spots do not function in misdirecting or scaring off predatory attacks as hypothesised for fishes that bear similar-looking eyespots, then what could they possibly be for?

NOTE lit. "little eye" L.

 

 

This ocellate swimming crab is exhibiting another possible line of
defense: the ability to autotomise (drop) its appendages when under
duress. Note that one claw and several walking legs are missing.
These will grow back over the next couple of moults 0.7X

 
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