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.
soft coral is a colony of countless tiny polyps.
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
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
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
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.
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
can contract when out of water.
St. John's Island, Aug 05
Shedding a layer of mucus.
Pulau Hantu, Mar 07
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
soft corals on Singapore shores
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.
Alcyoniidae recorded for Singapore
Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity
*from Y. Benayahu and L. M. Chou, 28 Feb 2010. On some Octocorallia
(Cnidaria: Anthozoa: Alcyonacea) from Singapore
+From our observation.
are difficult to positively identify without close examination.
On this website, they are grouped by external features for convenience
- Y. Benayahu
and L. P. van Ofwegen. Aug 2011. New
species of the genus Sinularia (Octocorallia: Alcyonacea) from
Singapore, with notes on the occurrence of other species of the
genus. The Raffles Bulletin of Zoology 2011 59. Pp. 117–125
[pdf, 1.08 MB]
- 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. [pdf, 913 KB]
- Michael P.
Janes and Lee Mei Wah. Octocoral
Taxonomy Laboratory Manual Results of the International Workshop
on the Taxonomy of Octocorals March 20-26, 2005 (pdf).
University of Kerala, India
Harry and Daniel Knop. 2005. Corals:
Indo-Pacific Field Guide
IKAN-Unterwasserachiv, Frankfurt. 305 pp.
Eric H. 2001. Aquarium
Corals: Selection, Husbandry and Natural History
T.F. H Publications. 464 pp
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
Brooks/Cole of Thomson Learning Inc., 7th Edition. pp. 963
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.