Tour of Ocean Habitats

Coral Reef Invertebrates


Fish aren't the only animals out on the reef.   The invertebrates are varied and fascinating in their own right.


Brittle Stars are related to starfish, but with long, slender arms.  They are usually found under rocks. This is the Spiny Ophiocoma Brittlestar, Ophiocoma echinata

Tube worms are related to the Christmas Tree Worms mentioned above.  Like the Christmas Tree Worms, Tube Worms or Feather Dusters live in a burrow sunk into the coral rock.

Fire coral is a distinctive coral form with its light brown color and flat-topped spires.  Brushing against it leaves a nasty, itching rash, hence the common name.  Note the fish making good use of this noxious coral as a safe retreat.

This small polychaete worm lives among the coral rocks. In many species, the long hairs are coated with irritating substances and quickly shed into the skin of an unsuspecting predator.


The Long-spined Sea Urchin (Diadema antillarum) used to be quite common in the Caribbean. Disease and some bad advice to divers (divers were told to kill the urchins to protect the reefs) cause the population to crash in the 1980's.  With the urchins out of the way, their real prey (algae, not the coral) grew rapidly, overcoming some reefs.

Giant clams like this are found on Pacific reefs, where they can grow to 3 feet across (they don't eat or trap divers!).  This specimen at Sea World in Orlando was only a couple of inches across.

These Soft Corals (AKA Dead-man's Fingers) are able to grow upright yet avoid the danger of being toppled in storms or big waves.  Their soft bodies bend with the waves.

Another soft coral.

Sea Cucumbers are unique, soft-bodied echinoderms related to sea urchins, sea stars (starfish) and brittle stars.

Another Sea Cucumber in a tank at Sea World.  The branching structures are the respiratory apparatus; many species can void these - as well as much of the viscera - in the face of a predator, giving the sea cucumber time to escape.

Yet another Sea Cucumber, this one on a rock in the Florida Keys.

A Sea Urchin in an aquarium.


Sponges are an important part of the reef.  In the Phylum Porifera, they feed by filtering their food out of the water using currents created by choanocytes (collar cells).  Some sponges deep on the reef have skeletons of calcium and may actually contribute more mass to the reef than the stony corals.

Squid are also common on reefs, and often come out at night.  All are predators.

Turning (or setting?) the table:  Sea Urchins on sale at a market in Paris.  A good portion of our diet comes from the oceans; its shores, and the coral reefs.




Proceed to Coral Reefs Proceed to Mangrove Swamps
Proceed to Coral Reef Fish Proceed to Sandy Shores
Proceed to Coral Reef Invertebrates Proceed to Rocky Shores