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Phylum Cnidaria > Class Anthozoa > Subclass Alcyonaria/Octocorallia > Order Alcyonacea
Leathery soft corals
Family Alcyoniidae
updated Mar 13

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

Where seen? Leathery corals are commonly seen on our Southern shores and in some places can grow quite large! Some look like fried eggs, others like a pile of discarded rubber gloves, and yet others like some bizarre leathery giant carnation or a big floppy pinwheel.

What are leathery soft corals? Leathery corals are soft corals that belong to the Family Alcyoniidae which has about 15 genera, the more commonly encountered ones on our shores being: Sinularia, Sacrophyton and Lobophytum. Together with the genera Alcyonium and Cladiella, these five genera make up the vast majority of octocorals found throughout the world.

Features: A colony is made up of tiny polyps embedded in a shared leathery tissue. Members of the family may have two kinds of polyps.

Autozooids have long stalks with eight tiny branched tentacles and emerge from the shared leathery tissue. Siphonozooids don't emerge from the shared tissue and function as water pumps for the colony. They appear as tiny holes or bumps in between the taller autozooids.

When the colony is out of water, the autozooid polyps are usually retracted completely into the shared tissue so that the entire colony appears smooth and leathery. The shared tissue might contract, but the entire colony cannot disappear into a crevice like some large anemones do.

Sometimes mistaken for sea anemones. When submerged, with the polyps expanded, the colony can appear rather 'furry' and may be mistaken for sea anemones.
Here's more on how to tell apart large sea anemones with long tentacles and large 'hairy' cnidarians.

The entire colony is quite stiff and hard, and is not soft and flexible. Like other soft corals, tiny spikes of calcium carbonate, called sclerites, are embedded in the tissue mass. These sclerites are used to identify these leathery soft coral species. Do not bend leathery corals or handle them roughly. Some may tear, while others contain dangerous toxins.

Many species of leathery coral periodically shed their upper layer as a mucus layer or dead waxy layer to get rid of sediments, algae and other unwanted substances.

Sometimes, very thin long 'strings' are seen emerging from leathery soft corals. These are the feeding tentacles of ctenophores, tiny animals that closely resemble the soft coral surface.

What do they eat? Leathery 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.

Sinularia sp. have only autozooids and do not have siphonozooids. A colony can take on a wide variety of shapes and even the same species may have different forms. The centre part of the colony can be tough and hard due to a dense mass of large sclerites.

Sacrophyton sp. have both autozooids with long stalks and siphonozooids. A colony is usually mushroom-shaped with a stem or stalk attached to a surface or buried in the sand. A colony usually looks like a mushroom; with a broad, flared smooth mushroom shaped top on with a 'stem' or base that is attached to a hard surface or buried in the sand. The flat top may be funnel-shaped, or extensively folded so the colony appears flower- or cabbage-like, but rarely elongated into lobes. A colony can reach 1m in diameter. Colonies have separate genders. Male colonies are smaller, while female ones are bigger. They reach maturity in 8-10 years. Some species of Sacrophyton can slowly creep quite a distance over time.

Lobophytum sp. have both autozooids and siphonozooids, but the autozooids have short stalks and often appear as mere tufts of tentacles. The siphonozooids do not emerge from the body membrance and are usually inconspicuous. A colony is encrusting, that is, the upper surface is the same diameter as the colony base and they do not have a stem or stalk. It may be dish- or bowl-shaped. The colony is thick and generally has lobes, ridges or rib-like structures.

Human uses: Leathery corals are considered toxic in the live aquarium trade. They produce substances that inhibit or stunt the growth of hard corals nearby.

Status and threats: None of our leathery corals are listed among the endangered animals of Singapore. However, like other creatures of the intertidal zone, they are affected by human activities such as reclamation and pollution. Trampling by careless visitors also have an impact on local populations.

Leathery soft corals can be quite large!
Pulau Hantu, Mar 05


Some colonies are mushroom-shaped
with a stem beneath a broad top.
Pulau Tekukor, May 07


Colony can contract when out of water.
St. John's Island, Aug 05



Shedding a layer of mucus.
Pulau Hantu, Mar 07

Different kinds of polyps

Smaller siphonozooids with
larger taller autozooids.
Pulau Hantu, Apr 09


Stinging tentacles produced by ctenophores
living on the leathery soft coral.
Sentosa, Nov 11

Leathery soft corals on Singapore shores


Autozooids on long body column.

Has siphonozooids.


Autozooids on short body column.

Has siphonozooids.


Autozooids on short body column.

Has siphonozooids.


Autozooids on short body column.

No siphonozooids.


Autozooids on short body column.

No siphonozooids.


Autozooids very short body column, star-like.

No siphonozooids. Spindle-shaped structures in common tissue.

Autozooids very short body column, star-like.

No siphonozooids. Prickly surface due to tiny spicules.
     

*Family Alcyoniidae recorded for Singapore
from Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore.
*from Y. Benayahu and L. M. Chou, 28 Feb 2010. On some Octocorallia (Cnidaria: Anthozoa: Alcyonacea) from Singapore
+From our observation.

  Family Alcyoniidae
  *Cladiella species (Black-and-white leathery soft coral) with species recorded for Singapore

*Lobophytum crassum
*Lobophytum pauciflorum
*Lobophytum sarcophytoides
Lobophytum soft corals seen awaiting identification
+Pimply leathery soft coral
+Pinwheel leathery soft coral

Lobularia pachyclados

Sacrophyton species (Omelette leathery soft coral) with species recorded for Singapore.

Sinularia species (Smooth leathery soft coral) with species recorded for Singapore

*Species are difficult to positively identify without close examination.
On this website, they are grouped by external features for convenience of display
.

Links

References

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