SCUBA Travel

Soft Coral, Dendronephthya hemprichi

Red Sea Soft Coral, Dendronephthya hemprichi
Red Sea Soft Coral, Dendronephthya hemprichi, taken on a night dive in Egypt by Tim Nicholson.

The soft coral is actually a colony of animals, each connected to its neighbour by living tissues. A single coral animal is a polyp - the attractive "flowery" projection.

Until recently soft corals were not thought to be reef-building, although they do secrete limestone. In their case this is as internal crystals called sclerites or spicules (yellow in the photo above). Because soft corals do not have large skeletons, they grow faster than hard corals

New research has revealed that massive parts of coral reefs are actually made from cemented sclerites.

Soft corals belong to a group of animals called Cnidarians. This also includes hard corals, sea fans, gorgonians, jelly fish and sea anemones.

A member of the Dendronephthya genus, these soft corals usually live below 10 m in areas with moderate or strong currents.

Soft coral on Dungus reef
Soft coral on Dungus Reef by Tim Nicholson.

Eight feathery tentacles surround the coral's mouth and whip food into it. They filter-feed: removing plankton from water flowing around the colony. Relatively recent data on soft corals indicates that they feed on very small planktonic particles, such as single-celled algae, rather than larger larvae as had previously been thought. Soft corals take in water to expand their body before feeding. This builds up a positive pressure inside the coral that supports the branches and trunk of the coral. A coral colony contracts by releasing the excess sea water from its system.

Yellow Soft coral
Soft coral by Tim Nicholson.

They can reproduce both sexually and asexually. A few days after full moon they spawn, when masses of eggs and sperm are released into the sea. New colonies can also be produced by budding.

Soft corals are primary colonisers, meaning that they fix themselves to structures before other marine life arrives. "Like rich rosettes of royal velvet, they decorate the rusting iron, transforming the unromantic metal stanchions into pillars that would grace a palace." wrote Robert Gibbings on observing soft corals for the first time in 1938.

Soft coral on shipwreck
Soft coral on the wreck of the Carnatic by Tim Nicholson.

According to the Encyclopedia of Life, Dendronephthya are among the most commonly traded soft corals. Between 1988 and 2002 at least 12,618 were sold globally (the U.S. was the largest importer, with 51% of the total Dendronephthya trade). However, corals in this genus are poor choices for aquarium hobbyists. They generally die within a few weeks, mainly because they lack photosynthetic algae symbionts (zooxanthellae) and must rely instead on filtering food particles and dissolved nutrients from the water.

You find Dendronephthya hemprichi in the Red Sea to the Western Pacific. The photos on this page were all taken in the Red Sea.

Phylum: Cnidaria > Class: Anthozoa > Subclass: Octocorallia > Order: Alcyonacea

Further Reading

News stories about coral
More soft coral photos
Soft coral is reef building
The Red Sea in Egypt Part II, Invertebrates, by Farid S Atiya, Elias Modern Printing House, 1994, ISBN 977-00-6697-4