Soft Coral: Gorgonians

by Lydia Weltmann

Found in the tropics and subtropics of the world, Gorgonians are a breed of soft coral colonies that typically have a tree-like appearance. Their branch-like parts distinguish them from other coral, as they can appear as sea fans, sea whips or blades, or they can be bushy. While they are all little wonders, each shape is actually a result of where they are found underwater. Those that make their home in shallow water with strong currents look more like fans, while those living in deeper, calmer waters tend to be more rod-like. This is because of how they filter their food from the currents. The fan catches more plankton than a rod would, so it is more beneficial in a stronger current where the food might otherwise get swept away.

Sea Fan

Sea Fan

Head Shoulders Knees and Coral

Gorgonian coral consists of a tough central stem attached to seafloor, rocks, or other coral. This stem, though tough, is also flexible so that it can bend in the current. The stem is also covered in a living outer layer, called a rind, which is then embedded with small polyps. Branches reach out from the stem, radiating outwards into the surrounding waters.

This coral tends to be several feet high, but then is only a few inches thick. It also has the same bright colors that other coral has, often appearing as yellow, red, or purple.

Filter Feeding

Bushy Gorgonian

Bushy Gorgonian

Like other corals, the Gorgonian feeds by filtering nutrients from the water. They are able to do this because of the polyps that cover the rind of the coral. Each polyp has eight tentacles that reach out to catch plankton and any other organic matter being carried past. The “fan” of a Gorgonian is usually spread out across the current to stop as much water as possible, therefore giving the polyps the opportunity to filter the water.

Some Sea Fans also have a symbiotic relationship with algae. The algae attach to the coral and lives there, and in return the algae photosynthesize and provide Gorgonians with energy and oxygen.

Sea Rod

Sea Rod

The Tenants

Many coral are home to various sea creatures, and the sea fan is no different. Hydrozoa, bryozoa, brittle stars, and pygmy sea horses have turned gorgonians into their personal dwellings. Not that you would ever see some of them… the pygmy sea horse for example has evolved to look similar to the rod-like gorgonians, therefore camouflaging themselves  just by floating in the water.

Aquarium Need-to-Know’s

Sea Fans make beautiful additions to any aquarium, but they are some of the most difficult coral to keep alive. Because they are filter feeders, there has to be a generous current passing by them. Generally the best way to accomplish this is to anchor them directly in the current, or at whatever point the current is strongest. Gorgonians also require a significant amount of light since most sea fans for sale are from shallower waters where they naturally have a lot of light.

Don’t let their fussy needs deter you though! They are wonderful additions to any tank!

Sea Whips

Sea Whips

 

 

Sources:

http://www.aquariumcreationsonline.net/seafan.html

http://animal-world.com/Aquarium-Coral-Reefs/Gorgonians

http://en.wikipedia.org/wiki/Gorgonian