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also known as "mushrooms," are undoubtedly
among the most interesting corals in nature.
They are soft-bodied and lack external calcareous
skeletons, despite being closely related to
stony corals, the Scleractinia. They are oddballs,
much as Heliopora coerulea (blue coral)
and Tubipora musica (pipe organ coral)
are soft corals that do produce an external
calcareous skeleton. They are found in three
or four families, and perhaps 13 genera, comprising
an unknown number of species. Even genus-level
identification is tenuous in this group.
Corallimorpharians are found in all oceans,
from tropical to polar and shallow to deep waters.
The most common types found in the aquarium
trade are believed to belong to one of six genera:
Actinodiscus, Rhodactis, Discosoma,
and Ricordea. The beautiful Psuedocorynactis
are not often available, but occasionally are
found as hitchhikers on live rock, and individuals
are commonly known as the orange ball corallimorph.
The single-polyped corallimorpharians are more
recent in evolutionary history than the stony
corals. This is interesting, because logically
it would seem that selection would act to have
corals produce skeletons as an adaptive measure.
This probably did happen, prior to the Scleractinia,
but at some point, a group of stony corals evolved
that could survive well without a skeleton.
How and why this happened is uncertain, but
I would offer some possible explanations.
are several taxonomic groups of corallimorpharians,
none of which are clearly defined. Although
most closely related to stony corals, they are
also closely related to the actinians, or sea
anemones. It is perhaps not surprising to know
that many of their modes of asexual reproduction
are also known in the anemones, as well as a
common "purse-string" type prey envelopment.
Some scleractinians are also very close in digestive
behavior and cnidae development to the corallimorpharians,
including the Caribbean Mycetophyllia
species. Some Indo-Pacific corals are able to
bail out of their skeleton and attach to substrate
using adhesive filaments. This behavior illustrates
the potential of coral polyps to exist without
animals are minimally colonial, although often
gregarious, forming clusters of polyps from
a few to many hundreds of individuals. They
tend to be most abundant in rubble areas in
shallow turbid water that are unsuitable for
stony corals. On reefs, corallimorpharians tend
to consist of small clumps of isolated individuals,
and they are often found under overhangs or
in recesses of the reef framework. Others, such
as the anemone-mimic giant corallimorph, Actinodiscus
fenestrafer, are found in more exposed locations
in shallow to mid-depth water. I have found
many of the more common species in the trade
in deeper water in marginal reef environments.
To this day, I have never seen the common "Actinodiscus"
red, blue, and striped-type mushrooms in the
is perhaps ironic that aquarists are so familiar
with these animals since they have been common
in the trade for such a long time, because they
are among the most unstudied and poorly understood
tropical corals. Little is known of their reproduction,
behavior, ecology, and biology. At least some
species are broadcast spawning.
one of the most interesting observations about
these animals that has occurred from their long-term
husbandry is their competitive ability. They
are resistant to disease, and extremely competitively
dominant. Nothing seems to settle near corallimorpharians,
and I have never seen or heard of anything able
to take over space occupied by corallimorpharians.
Co-existence with other species is possible,
but the corallimorpharians never seem to "lose
a battle." They are the only animals which
I have found able to resist nearby settlement
and competition by Aiptasia anemones.
For this trait alone, they must be admired!
probably know more about these animals than
any other group of people. It is important for
us to maintain living stocks of these animals,
for so little is known of their taxonomy and
distribution. Some may be exceedingly rare and
never described. I would urge everyone to work
diligently at maintaining widespread propagated
stock of corallimorpharians since some of them
may never be found again. This should not be
difficult as they survive and reproduce well
in aquaria, and are tolerant of most any conditions
that exist in aquaria. For husbandry requirements
and more information about these animals, please
refer to the chapter on these fascinating animals
in my book, Aquarium
Text by Eric Borneman.
Photos by Reef Central members.
A special thanks goes out to Dave Bayne (Nanook)
for his assistance on this project.
Reefkeeping Magazine Reef Central, LLC-Copyright © 2008