Diversity of reef organisms

A healthy reef supports a rich diversity of organisms.  CLICK ON an icon to see some examples of Caribbean reef plants and animals. Throughout the VIRTUAL DIVE we’ll see these and many other reef-dwellers and will study what they do, how they behave, and how they interact. 

hot buttons for diversity section of BIOLOGY OF CARIBBEAN CORAL REEFS website diversity of corals diversity of gorgonians diversity of sponges diversity of worms diversity of molluscs diversity of crustaceans diversity of echinoderms diversity of tunicates diversity of turtles diversity of fishes diversity of sharks/mammals
icon for coral-diversity section of BIOLOGY OF CARIBBEAN CORAL REEFS website


There are about 50 common species of corals in the Caribbean Sea. A few representatives are featured below. Some commonly encountered relatives of Caribbean corals, other than gorgonians, are presented below the corals section.

seahorse "dive leader" in BIOLOGY OF CARIBBEAN CORAL REEFS website photograph of a coral reef taken from a video

"On this quick swim over the reef crest we’re looking at about one-tenth of the 50-or-so
common species of stony corals that live in the Caribbean region"
- Cayman Brac

A selection of stony corals:

NOTE hard corals are known as stony, or scleractinian, corals which separates them from soft, or alcyonacean, corals.  Reef-building scleractinians are also referred to as hermatypic corals

photograph of stony coral Agaricia tenuifolia
Lettuce coral Agaricia tenuifolia 3X
photograph of cathedral coral Dendrogyra cylindrus
Pillar or cathedral coral Dendrogyra cylindrus 0.2X
photograph of brain coral Diploria sp.
Brain coral Diploria sp. 0.5X
photograph of staghorn coral  Acropora cervicornis
Staghorn coralAcropora cervicornis 0.5X
photograph of flower coral Mussa angulosa
Flower coral Mussa angulosa 0.3X
photograph of finger coral Porites porites
Finger coral Porites porites 0.25X
photograph of boulder coral Montastraea annularis
Boulder coral Montastraea annularis 0.1X

Relatives of Caribbean corals

Caribbean relatives of corals, other than gorgonians, include hydroids, hydrocorals, siphonophores, jellyfish, and sea anemones.  All are classified in the Phylum Cnidaria.  All have the common properties of a 2-cell-layer construction, blind gut (mouth but no anus), and nematocysts for capturing food and for protection. Cnidarians exist in 2 basic forms: polyp (like a sea anemone or coral) and medusa (like a jellyfish). There are 3 Classes in the Phylum Cnidaria and representatives of each are featured below. Class Hydrozoa includes hydroids, fire corals, and Portuguese man-of-wars. Class Anthozoa includes corals, sea anemones, and gorgonians. Class Scyphozoa includes jellyfishes.

NOTE also known as stinging cells.  However, they are not cells; rather, are complex microscopic structures located within cells capable of discharging a thread at great velocity to entangle or poison a prey or predator

seahorse dive leader photograph of an anemone Condylactis gigantea taken from a video

The giant anemone is one of the largest Caribbean sea anemone. Note in the first video the bare rocks around the anemone, a likely result of its stinging cells. The second video shows a blue-tipped morph of the species, one of several colour varieties. The function of the colour is unknown - Bonaire 2008

NOTE Condylactis gigantea


photograph of hydroid Sertularella speciosa
Polyp form of the hydrozoan Sertularella speciosa. The polyps, visible as tiny white projections. Two types of polyps are present: feeding & reproductive 5X
photograph of a fire-coral colony Millipora sp.
Fire coral Millipora sp. is a hydrozoan named for its extremely potent stinging cells borne by special defensive polyps. Thus, there are 3 types of polyps in Millipora 1X
photograph of rose lace-coral Stylaster roseus
As do most corals and all species shown here, rose lace-corals Stylaster roseus exist in colony form, with all polyps being inter-connected for sharing of nutrients
photograph of Portuguese-man-of-war Physalia sp. courtesy Cindy Young
The Portuguese-man-of-war Physalia sp. is a colony of polyps, one serving as a flotation bell, and others for feeding, defense, and reproduction borne on tentacles 1X
photograph of 2 fishes caught in the tentacles of a Portuguese-man-of-war Physalia sp.
Two fishes caught by a Physalia and stranded on the shore. Large numbers of extremely toxic nematocysts enable the catching of relatively large prey 1X
photograph of a chondrophore, the by-the-wind-sailor Velella velella
By-the-wind sailors Velella sp. have a colonial construction similar to that of Physalia, with polyps for flotation, feeding, defense, and reproduction 1.5X
photograph of sea anemone Condylactis gigantea
The largest sea anemone in the Caribbean, Condylactis gigantea 0.4X. The stinging cells, which are not toxic to humans, are located in the white clusters on the tentacles
photograph of sea anemone Lebrunia danae
The sea anemone Lebrunia danae inhabits crevices and extends its tentacles at night. Unlike Condylactis, which is harmless to humans, Lebrunia can give a potent sting 1X
photograph of jellyfish Aurelia aurita
The predominant life phase of a jellyfish Aurelia aurita is the medusa form, but it does have an alternate life phase, the polyp 0.3X
seahorse dive leader for diversity section of BIOLOGY OF CARIBBEAN CORAL REEFS website photograph of fire coral on reef taken from a video

Fire corals are obvious features of Caribbean reefs. If you look closely at the specimen in the beginning video, you may see a white fuzz covering the branches. These are the defensive polyps, bearing highly toxic stinging cells. Although you shouldn't be touching anything on the reef, be especially careful with these. Fire corals are aggressive colonisers on the reef and, as shown by the second video, will out-compete gorgonians and other reef dwellers for living space - Turks & Caicos 2003

NOTE Millepora spp.