Table of Contents Coral Reef Cart Collection

Cnidarians: Octocorallia

Alcyonacea: Soft Corals and Gorgonians

Specimens

gorgonian

general information

Classification

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  Phylum Cnidaria, Class Anthozoa, Subclass Octocorallia, Order Alcyonacea
  
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  Note that the subclass Octocorallia also includes Order Helioporacea (Blue Coral) and Order Pennatulacea (Sea Pens)
  

Distribution

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  Octocorals are found in all the world’s oceans. The greatest diversity is in the tropical western Pacific.
  

Habitat

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  Octocorals are found in both shallow tropical marine habitats as well as in deep benthic communities.
  

Appearance and Behavior

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  All octocorals have eight feather-like tentacles that surround the mouth of each polyp. These tentacles are often fringed and contain nematocysts which are used for protection and to incapacitate prey.
  
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  Colonies are usually attached to the substrate at a single point at the base of a stem and most species have some form of branching. They may resemble fans, bushes, and whips. In addition, some colonies are encrusting.
  
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  Although they don't secrete calcium carbonate as prolifically as hard corals, soft corals do contain spiny skeletal elements called sclerites that are found in the jelly-like tissue between polyps. Sclerites are made of protein and calcium carbonate and give soft coral support to allow them to achieve their vertical structures. The sclerites also give their surfaces a spiky or grainy texture.
  
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  The inner core of a soft coral may also contain gorgonin; a flexible, fibrous protein. This gives the soft corals that contain it the ability to flex with the ocean waves and currents.
  
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  When a soft coral animal dies, its tissue decomposes and disappears. The exceptions to this are gorgonian, blue coral, and organ pipe coral.
  

Diet

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  Some soft corals have zooxanthellae that provide glucose, glycerol and amino acids to the corals.
  
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  Some soft corals do not contain zooxanthellae and feed on zooplankton and debris only.
  
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  The branching shape and large size of many octocorals helps their polyps capture food from the water as it passes by the colony
  

Predators

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  Many soft corals exude mucus with traces of chemicals that repel other organisms, such as sponges and algae which might otherwise grow too close or over the top of the corals.
  
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  Brittle stars and marine worms that live on the octocoral in order to have better access to food particles may feed on the coral themselves.
  

Reproduction and Development

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  Three types of reproduction occur in octocorals: broadcasting of eggs and sperm, internal brooding of larvae, and external brooding of larvae.
  

Remarks

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  Some of the soft corals produce substances such as terpenoids that are being studied for their toxic effects on human cancer cells.
  

To Notice

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  Mention that most soft corals would not leave behind a complete skeleton, but gorgonians do.
  
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  Notice the shape of the gorgonians and how that shape would enable them to have contact with the water for nourishment purposes.
  
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  Point out that the sea fan would be at right angles to the current.
  
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  Mention that the live sea fan would have a different color. Show photo.
  
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  Show photo of deep water gorgonians that resemble the misc. gorgonian.
  

SPECIMEN detail

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  Distribution: It is found from Bermuda to Curacao, including the Florida Keys and Western Caribbean. However, it is not found in the Gulf of Mexico.
  
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  Habitat: It is primarily found on band and patch reefs. In addition, it can be found in near-shore areas with heavy wave action and also on deeper reefs.
  
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  Appearance: The sea fan can grow to be 180 cm by 150 cm. It is usually purple but can vary to its less common colors of yellow-orange, yellow, and brown. The pigments are in the spicules. The polyps are white. The common sea fan will orient so that the "fan" is perpendicular to the motion of the waves. This orientation only occurs in the adult sea fans. The young will grow in any direction, but as they mature will slowly shift until they are facing the current.
  

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  Diet: It is carnivorous, feeding on zooplankton, especially at night. Also, derives nourishment from its zooxanthellae.
  
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  Predators: The carnivorous gastropod Cyphoma preys on octocorals such as the sea fan. The sea fan does have chemical defenses that somewhat reduce this predation.
  

When infected by the fungus Aspergillus, the sea fan will respond with more sclerites in the area to contain the fungus.

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  Mortality: The lifespan is unknown. Most commonly gorgonian corals are destroyed by wave energy or by overgrowth of organisms, such as encrusting bryzoans and fire coral.
  
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  Reproduction: Gorgonian corals reproduce asexually by cloning or fragmentation, with external fertilization.
  

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  Conservation: The sea fan is officially protected in some coral reef areas.
  
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  Remarks: The sea fan is popularly collected for use in aquariums and as souvenirs. As a colorful addition to coral reef habitats, its presence also is important to ecotourism
  

Gorgonian (species unknown)

The shape of this gorgonian is a contrast to the Common Sea Fan gorgonian.

Since its exact name is unknown, below is some general information about gorgonians.

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  Distribution: Gorgonians are found throughout the oceans of the world, especially in the tropics and subtropics.
  
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  Habitat: Gorgonians are found in shallow waters, though some have been found at depths of several thousand feet.
  
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  Appearance: They can be whip-like, bushy, or even encrusting. They can be brightly colored, often purple, red, or yellow. They may be up to several feet high.
  

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  Diet: Some gorgonians have zooxanthellae and derive some or most of their nutrition from them. Others, especially deep water gorgonians, use only their polyps to capture food. Most gorgonian polyps are expanded during the day for feeding, rather than at night.
  
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  Remarks: Other fauna such as hydrozoa, bryozoa, and brittle stars are known to live within the branches of gorgonian colonies.