Coloration of reef organisms
Coloration in reef organisms

hot buttons for colours section of Biology of Caribbean Coral Reefs website
Topics relating to colours include how colours are created, considered here, and HOW COLOURS ARE PERCEIVED and the FUNCTION OF COLOURS, dealt with in other sections.

How colours are created

Colours in marine animals are created by pigment deposits, considered here, and by CHROMATOPHORES, by refraction of light from STRUCTURAL ELEMENTS, and by the PRESENCE OF OTHER ORGANISMS.

How colours are created: pigment deposits

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

"Aren't these little fishes pretty?! Their colours are mostly from chromatophores, although some of the the black colours are from pigment deposits in cells which don't change in size...and in these shiners the reflectivity is caused by white pigments in cells that also don't change in size." - Little Cayman 2003

NOTE unknown ID

drawing showing mechanism of production of black and white colours in fishes
Black is a common colour in reef fishes, such as the banded butterflyfish Chaetodon striatus shown here. It may result from black melanophores that can be regulated in size, but it and almost all white colours in fishes can also result from pigment deposits either within cells or in tissues that cannot be regulated in size as are the chromatophores. White coloration in fishes is created from light reflecting off a deeper layer of pigment-containing cells known as iridiphores. In the banded butterflyfish featured here, the black colours are from light reflected from melanin-containing cells in the dermis, while the white colour is from light reflected from a deeper iridiphore layer.

NOTE "black" "to carry" these are a type of chromatophore specialised to carry the black pigment melanin. This is the same pigment that our own bodies manufacture when tanning in the sun

photograph of a peacock flounder Bothus lunatus
Peacock flounders Bothus lunatus have one or two larger deposits of melanin pigment along the midline of the body, and several smaller deposits on the peripheral fins. While some of these deposits are more-or less permanently visible, the fish can augment their size and intensity by increasing the size of adjacent melanophores. Such adjustments allow finer control on the camouflaging effect.




Peacock flounder Bothus lunatus 0.5X

photograph of a king-helmet shell Cassis flammea
In molluscs, shell colours derive mainly from coloured matter within the crystalline photograph of a Caribbean fighting conch Strombus pugilismatrix of calcium carbonate that makes up the shell. The coloured matter may be pigment deposits, including some melanin, but more commonly are deposits of coloured by-products of the animal's own metabolism.

Colorful king-helmet shells Cassis
are now extremely rare
because of over-collecting. This
is a museum specimen 0.4X

West Indies fightig conch
Strombus pugilis

photograph of flame augers Terebra turinus showing imprecise colour pattern between individuals
Deposition of pigments in the shells of molluscs is quite imprecise, as shown by this array of flame augers from Barbados. So, while the pattern of pigment deposition to form the "flames" is certainly characteristic for the species in these 4 individuals, considerable variation exists both between and within individuals in the precise details of the pattern.





Flame augers Terebra taurinus 1.2X

photograph of spiny lobster Justitia longimanus
Lobsters, shrimps, and other crustaceans have an abundance of red caroteoid pigments. These exist both as colour-changeable chromatophores in the skin underlying the exoskeleton, and as pigment deposits in the exoskeleton itself. The pigment is obtained from seaweed and phytoplankton foods directly, or from animal prey that themselves eat the plant material.

NOTE lit. "outside skeleton". In arthropods it is the hard outer non-living casing conissting of protein and carbohydrates impregnated with calcium salts. The exoskeleton is periodically moulted, sometimes several times per year, to allow the animal to grow in size




Spiny lobster Justitia longimanus
containing carotenoid pigments 0.2X

Colours in most marine invertebrates, such as sponges, are also created by pigment deposits. Sponges consist of aggregations of cells with no tissues or organs. The cells are of different types, some involved in water flow and feeding, and others with protection, reproduction, and defense. One type, known as a chromatocyte (lit. "colour cell), contains pigments and imparts the overall colour to the sponge. The photographs below show a variety of sponge colours. Photograph below Right courtesy Anne Dupont, Florida.
photograph of purple tube sponges photograph of colorful Caribbean sponges photograph of rope sponges courtesy Anne Dupont, Florida
Above: purple tube sponge Aplysina sp. 0.2X
Middle: pink vase sponge Niphates digitalis 0.25X Right: rope sponge Aplysina cauliformis 0.25X

photograph of a school of shiners
Shiners and other reflective fishes such as sardines, anchovies, and the like, have a layer of iridiphores in their skin, similar to the type noted above for the banded butterflyfish. In shiners, however, the iridiphores differ somewhat in that they are filled with white, reflective, crystalline guanine and act like mirrors, reflecting light almost unchanged from their surfaces.

NOTE guanine is a by-product from the breakdown of nucleic acids. Mirror-reflectivity and its role in camouflae is considered elsewhere: FUNCTIONS OF COLOURS: DEFENSE/CAMOUFLAGE

hot button for how colours are created part of BCCR hot button for how colours are perceived part of BCCR hot button for functions of colours part of BCCR