> Class Anthozoa > Subclass
Zoantharia/Hexacorallia > Order Corallimorpharia
learn only 3 things about them ...
They are animals and not plants!
They are distinguished from sea anemones by an upturned
often grow over coral rubble or stones. Don't step on
seen? These little disk-shaped animals are commonly encountered
on our Southern shores, where they can sometimes form carpets over
What are corallimorphs? Corallimorphs
are Cnidarians that belong to the
same Class Anthozoa as sea anemones.
There are about 50 species of known corallimorphs. They are found
in all parts of the ocean, from shallow to deep waters, from the tropics
to even the poles. Some deeper water species can reach 1m in diameter!
Features: Those seen on our shores
have oral disks 1-2cm in diameter. Like sea anemones, corallimorphs
are solitary polyps, although they are often found in groups and may
sometimes carpet large areas of coral rubble.
Corallimorphs are distinguished by an upturned mouth in the centre
of the oral disk. Most other sea anemones and corals have inward turning
Corallimorphs also have a narrow body column, although this is usually
hidden by the broad oral disk. The body column is usually buried in
the ground or attached to a surface. Some corallimorphs tuck their
oral disk into their body columns when they are exposed out of water,
so they look like blobs.
Their internal structure is similar to that of hard corals. But unlike
hard corals, corallimorphs don't produce a hard skeleton. Corallimorphs
also lack long tentacles.
Corallimorphs usually have two types of tentacles: one type found
on the edge of the oral disk and another kind on the surface of the
oral disk. Their tentacles are usually short, some so short that the
tentacles are merely bumps.
Corallimorphs come in a wide range of colours and textures on the
What do they eat? Most corallimorphs
harbour zooxanthellae (symbiotic algae) inside their bodies. The symbiotic
algae carry out photosynthesis and may contribute nutrients to the
host. Corallimorphs also filter feed, trapping edible bits in mucus
that coats their bodies.
Corallimorphs also have stingers like
other Cnidarians. Some large corallimorphs can reach 30cm across
or more and can eat fishes! These fishes are trapped in the muscular
oral disc, similar to the way a Venus Flytrap plant catches its prey.
Corallimorphs also produce toxins that seem to injure or kill hard
corals or other encrusting organisms that settle near them.
Corallimorph friends: Animals
such as acoel flatworms
and tiny shrimps are sometimes seen on corallimorphs.
Corallimorph babies: Corallimorphs
can reproduce by budding or by fission, in which the parent divides
to produce a new polyp.
Role in the habitat: Corallimorphs
are secondary colonisers that rapidly cover empty spaces in a reef,
e.g., dead corals. Corallimorphs are more resistant against pollutants
and are thus used as indicators of pollution.
Status and threats:
Corallimorphs are not 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, and over-collection also have an impact on local
Forms a living carpet.
Sisters Islands, Dec 03
St. John's Island, May 05
Underside is usually smooth.
Pulau Hantu, Aug 04
Tucked into its body column.
St. John's Island, Aug 07
Covered with tiny brown acoel
St. John's Island, Jan 06
Corallimorpharia seen on Singapore Shores
commonly seen awaiting identification
are difficult to positively identify without close examination.
On this website, they are grouped by external features for convenience
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
- 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.