soft corals text index | photo index
Phylum Cnidaria > Class Anthozoa > Subclass Alcyonaria/Octocorallia
Soft corals
Order Alcyonacea
updated Mar 13

if you learn only 3 things about them ...
They are animals! Although they look like plants.
They don't produce a hard skeleton.
Each soft coral is a colony of countless tiny polyps.

Where seen? Soft corals are commonly seen on many of our shores. Some resemble flowery bushes, others giant leathery disks. Yet others are tiny and overlooked. They are found growing on boulders and other hard surfaces, as well as among coral rubble and living hard corals on the reef flats.

What are soft corals? Soft corals belong to Phylum Cnidaria which includes the more familiar sea anemones, hard corals and jellyfishes. Soft corals are members of the Subclass Alcyonaria/ Octocorallia that includes gorgonians and sea pens.

Within this Subclass, the Order Alcyonacea includes flowery soft corals (Family Nephtheidae) as well as leathery soft corals (Family Alcyoniidae).

Features: Soft corals are colonies of tiny, individual polyps linked to one another. Soft corals can look like branching bushes or trees. They may also be flatter and look like mushrooms. When exposed at low tide, they often flop over and look like a pile of jelly or fried eggs! When submerged, however, they expand into beautiful plant-like forms and some appear 'furry' as the tiny polyps expand.

Soft coral polyps have 8 (or multiple of 8) tentacles that are pinnate (branched or feathery). Some soft corals like leathery soft corals have two kinds of polyps: Autozooids have long stalks with eight branched tentacles and emerge from the shared leathery tissue. Siphonozooids may be much shorter polyps or don't even emerge from the shared tissue and function as water pumps for the colony.

Sometimes mistaken for sea anemones. Some large sea anemones and large leathery and flowery soft corals may be mistaken for one another. Here's more on how to tell apart large 'hairy' disk-like animals on the shore.

Soft support: Although there are some exceptions, many soft corals don't produce a hard skeleton. Instead in colonial soft corals, the polyps are connected by a shared tissue.

Tiny spikes of calcium carbonate, called sclerites, are embedded in the tissue mass. These sclerites are used to identify soft coral species. In some, the sclerites are far apart resulting in a more floppy soft coral. In others, the sclerites are closer or fused together to form firmer support. The entire tissue mass is covered with a skin and the polyp tentacles emerge through this skin. In some soft corals, the skin can be quite tough and leathery looking, thus these are often called leathery soft corals. Out of water, soft corals may flop over and may look small. But underwater, they expand and spread out to maximise the feeding surface.

What do they eat?
Most soft corals feed on plankton, some also feed on finer particles. Like other cnidarians, soft coral polyps have tentacles with stingers to capture food.

Many soft corals harbour microscopic, single-celled symbiotic algae (zooxanthellae) within their bodies. The algae undergo photosynthesis to produce food from sunlight. The food produced is shared with the host, which in return provides the algae with shelter and minerals.

Role in the habitat: Some soft corals are homes to tiny animals. Some tiny animals eat soft corals and look just like their much larger prey.

Coral babies: Soft corals can reproduce asexually: budding of new polyps enlarges the colony. However, they also reproduce sexually. The polyps may produce sperm or eggs. The eggs develop into free-swimming larvae that drift with the plankton before settling down to start a new colonies.

Human uses: Soft corals protect themselves with unusual substances which are being studied for possible anti-cancer properties. Soft corals are also harvested from the wild for the aquarium trade. Living coral reefs, however, are worth far more to humans when they left alone. Reefs bring in tourists which generate business beyond the shore (e.g., hotels, restaurants and travel-related industries).

Status and threats: Like other creatures of the sea, soft corals are threatened by human activities that degrade or destroy the habitat.
Trampling by careless visitors, and over-collection also have an impact on local populations.

Flowery soft coral
Beting Bronok, Aug 05


Ball soft coral
Beting Bronok, Jul 08



Leathery coral
St. John's Island, Aug 05


Broad feathery soft coral
St. John's Island, Aug 05



Fine feathery soft coral
Beting Bronok, Jun 06

Tiny colourful brittle stars are
sometimes seen in soft corals.
Tuas, Nov 03

Small ovulid snails are
sometimes seen in soft corals.
Chek Jawa, Apr 08

Tiny red nose shrimp are
sometimes seen in numbers in flowery soft coral.
Tuas, Nov 03

Soft corals on Singapore shores


     


Order Alcyonacea recorded for Singapore
from Y. Benayahu and L. M. Chou, 28 Feb 2010. On some Octocorallia (Cnidaria: Anthozoa: Alcyonacea) from Singapore
*Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore.
Groups from Fabricius, Katharina and Philip Alderslade, 2001. Soft Corals and Sea Fans.
+from our observation

STOLONIFERA GROUP
  +Family Clavulariidae
  Carijoa sp. (Knobbly soft coral)

ALCYONIINA GROUP
  Family Alcyoniidae (leathery soft corals) with list of species recorded for Singapore

  *Family Nephtheidae (flowery soft corals)
  *Dendronephthya sp.

  Family Paralcyoniidae
  Studeriotes spinosa

  Family Xeniidae
  Sansibia flava (Broad feathery soft corals)
+Heteroxenia sp. (Xenia soft coral)

+Brown feathery soft corals

SCLERAXONIA GROUP
  Family Briareidae
  Briareum sp. (Fine feathery soft corals)
Briareum excavatum

Some Gorgonians are included in this group

Other 'soft coral' orders


Order Helioporacea
  Family Helioporidae
  Heliopora coerulea (Blue coral)

Order Pennatulacea (sea pens)

Threatened soft corals of Singapore
see list of threatened cnidarians

Links

References

  • Y. Benayahu and L. M. Chou, 28 Feb 2010. On some Octocorallia (Cnidaria: Anthozoa: Alcyonacea) from Singapore, with a description of a new Cladiella species. The Raffles Bulletin of Zoology. Pp. 1-13.
  • Borneman, Eric H. 2001. Aquarium Corals: Selection, Husbandry and Natural History T.F. H Publications. 464 pp
  • Fabricius, Katharina and Philip Alderslade, 2001. Soft Corals and Sea Fans. Australian Institute of Marine Science and the Museum and Art Gallery of the Northern Territoriy. 264 pp
  • Edward E. Ruppert, Richard S. Fox, Robert D. Barnes. 2004.Invertebrate Zoology Brooks/Cole of Thomson Learning Inc., 7th Edition. pp. 963
  • Pechenik, Jan A., 2005. Biology of the Invertebrates. 5th edition. McGraw-Hill Book Co., Singapore. 578 pp.
  • Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore. National Council on the Environment. 163pp.
  • Ng, P. K. L. & Y. C. Wee, 1994. The Singapore Red Data Book: Threatened Plants and Animals of Singapore. The Nature Society (Singapore), Singapore. 343 pp.
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