Coloration of reef organisms
column spacer Coloration of reef organisms
  hot buttons for colours section of Biology of Caribbean Coral Reefs website
This section continues the topic of how colours are created. Topics of HOW COLOURS ARE PERCEIVED and the FUNCTION OF COLOURS can be accessed via the icons.

How colours are created


Colours in marine animals are created by presence of other organisms, considered here, and by PIGMENT DEPOSITS, by CHROMATOPHORES, and by STRUCTURAL ELEMENTS.


How colours are created: presence of other organisms

seahorse dive leader for Biology of Caribbean Coral Reefs photograph of reef to show muted colours of invertebrates "We're always talking about how colorful the reef is, but take a look...mostly the corals are shades of brown - probably because their internal symbionts are brownish in colour. Most of the bright reef colours actually come from fishes and sponges." - Turks & Caicos 2007

photograph of a boulder coral Montastrea sp.
Colours of corals are predominantly brownish hues of green, purple, and yellow derived in part from pigments made by the corals themselves, and also from the brown colour of their photosynthetic symbiotic plant cells.



Boulder coral Montastrea sp. 0.5X



  illustration to show location of pigments and symbionts in a coral polyp
The pigments are usually in the epidermis, and lie above the symbionts in the deeper gastrodermis.
  illustration showing how pigments and symbionts contribute to colours in corals   illustration showing how deeper reflective layers increase light exposure of symbionts
  Sunlight penetrates the skin of the polyp and reflects off both pigment granules and symbionts, imparting in the example shown here an overall brownish-pinkish tinge. The pigments partially shade the symbionts and may provide protection in high UV-light conditions. Dove et al. 2001 Coral Reefs 19: 197   In comparison, coral species that llive in low-light conditions may have auxillary reflective pigments located below the symbionts that bounce light back
up to the symbionts, perhaps adding different hues to the overall colour

photographs of various purplish-coloured spongesIn a similar way, colours of sponges are a combination of pigments and the colour of their cyanobacterial symbionts. These may comprise up to 1/3 the volume of the sponge, and impart mauve or violet hues to their hosts.

NOTE also known as blue-green algae. More on their relationship with sponges can be found at PRIMARY PRODUCERS: PHOTOSYNTHESIS IN INVERTEBRATES:SPONGES

Sponges: Top L & Bottom L: branching tube sponge Pseudoceratina crassa

Top Mid: azure vase sponge Callyspongia plicifera

Top R: unknown

Bottom R: branching vase sponge Callyspongia vaginalis


photograph of opisthobranch Elysia crispata courtesy Anne Dupont, Florida
Finally, certain algal-sucking snails that take up and utilise the photosynthetic chloroplasts of their plant foods for their own nutrition may reflect the colours of the symbionts. Photograph courtesy Anne Dupont, Florida.

NOTE for more information on these snails and their chloroplasts go to PRIMARY PRODUCTIVITY: INVERTEBRATES: SNAILS


Lettuce sea slug
Elysia crispata

hot button for preemptive competition part of Biology of Caribbean Coral Reefs hot button for overgrowth competition part of Biology of Caribbean Coral Reefs hot button for chemical competition part of Biology of Caribbean Coral Reefs 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