Spectacular Facts About Sea Fans (Gorgonians)

01
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What Are Sea Fans?

Donateur Wreck, Cote d'Azur, France
Borut Furlan/WaterFrame/Getty Images

Sea fans are a type of soft coral that is often found in warm waters and around reefs. There are also soft corals that live in deep waters. These are colonial animals that have a beautiful, branching structure that is covered by a soft tissue.​ This image shows sea fans around a shipwreck.

Gorgonians are in the Class Anthozoa, which also includes other soft corals (e.g., sea whips), sea anemones and stony or hard corals. They are in the subclass Octocorallia, which are soft corals that have eightfold radial symmetry. 

 

02
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Sea fans have feathery polyps.

Sea fan, showing polyps, Fiji
Danita Delimont/Gallo Images/Getty Images

Like other corals, gorgonians have polyps. The polyps have tentacles arranged as a pennate, which means they have one main tentacle with branches off of it, like a feather. They can withdraw into the leathery tissue of the coral.

Feeding

Sea fans use their polyps to trap small food particles, such as phytoplankton and bacteria. The sea fan usually grows so that it is best oriented so that the prevailing water current flows over the sea fan so food can be easily trapped.

The polyps are connected by fleshy tissue.  Each polyp has a digestive cavity, but it is connected by tubes in the tissue. The whole sea fan is supported by a central axis (which looks a bit like the stem of a plant or trunk of a tree). This is made of a protein called Gorgon, which is how these animals get the name gorgonians.  Although this structure makes the sea fan look like a plant, it is an animal.

Some gorgonians are inhabited by zooxanthellate, dinoflagellates which conduct photosynthesis. The gorgonian benefits from the nutrients produced during that process. 

03
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Sea fans host other marine life.

Pygmy seahorse on gorgonian
Pygmy seahorse on gorgonian. Jeff Rotman/Photolibrary/Getty Images

Sea fans may support their own community of creatures. Tiny pygmy seahorses perch on their branches, using their long, prehensile tails to hold on.  One type of seahorse which lives on these corals is the common pygmy or Bargibant's seahorse.  This seahorse has two color morphs - one a pinkish color and one yellow. The seahorses have knobby bodies that blend in perfectly with their coral home. Can you see the pygmy seahorse in this image?

Bivalves, sponges, algae, brittle stars and basket stars also live on sea fans.

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Sea fans are colorful.

Reef with variable gorgonians (Paramuricea clavata)
Reef with variable gorgonians (Paramuricea clavata). Borut Furlan/WaterFrame/Getty Images

Gorgonians can get pretty large - up to 3 feet tall by 3 feet wide. They can be a variety of colors, including pink, purple, yellow and sometimes white. You can see a colorful collection of sea fans in this image. 

Although the sea fans have branches, most of these organisms are flat, rather than bushy.

Sea Fan Reproduction

Some gorgonians reproduce sexually. In this situation, there are male and female colonies of sea fans that broadcast sperm and eggs into the water column. The fertilized egg turns into a planula larvae. This larva swims at first and then metamorphoses and settles to the bottom and becomes a polyp.

From the first polyp, additional polyps bud to form a colony. 

These corals may also reproduce asexually, such as when they bud from one polyp, or produce a new colony from a fragment of coral. 

05
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Sea fans may be used as souvenirs.

Colorful gorgonian
Colorful gorgonian. Photosub Images/Moment/Getty Images

Sea fans may be collected and dried and sold as souvenirs. They also are harvested or grown for display in aquariums.

One of the best uses of sea fans is in the wild. Sea fans create a colorful, calming presence while you're scuba diving or snorkeling near a coral reef

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