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the word says it all. Living together in varying
degrees of intimacy is the very root of coral
reef existence. The "five-dollar"
word for togetherness is symbiosis and without
the various symbioses of coral reef animals,
there would be no coral reef. It all starts
with the symbiosis of a dinoflagellate and a
coral animal, and here both partners presumably
benefit from the arrangement; the corals get
food and the algae get protection.
Although commonly thought of as being beneficial
to both parties, such arrangements, termed mutualisms,
are examples of only one of several types of
symbioses. The types of symbioses may be thought
of as a continuum of arrangements. The "positive"
extreme would be these mutualistic arrangements
where both parties benefit. Probably the most
well-known mutualism is between the various
anemone fishes and sea anemones. Indeed, this
relationship is so well known that it is virtually
an icon of coral reefs. I suspect there is no
true reef aquarist who doesn't, deep in his
or her heart, want to have their own version
of Nemo snuggled into an anemone somewhere in
their system. Similar mutually beneficial relationships
would be those of cleaner wrasses or cleaner
shrimps and their clientele.
A different type of symbiosis is commonly described.
This is an arrangement which benefits one of
the partners, while neither benefitting nor
is harming the other. Termed commensalisms,
this is the arrangement commonly described for
animals such as porcelain anemone crabs and
their host anemones. These crabs are primarily
suspension-feeding animals, and they use their
large basket-like feeding appendages to sweep
the water to get their food. They don't harm
the anemones, but they benefit by gaining protection
from their host. Few fish will hazard getting
eaten by an anemone simply for the chance to
snack on the crab.
similar arrangement is often said to exist for
the beautiful Periclimenid shrimps living on
sea anemones throughout the tropics and well
illustrated in these images. Here the shrimp
is presumed to get the benefits of protection
while the anemone gets no benefit whatsoever
(See, for example, Mihalik and Brooks, 1997).
These relationships, however, may be significantly
more complex than this simple explanation indicates.
Some of these shrimps, such as the relatively
common Periclimenes pedersoni, found
throughout the Caribbean, may be a cleaner shrimp
(Zann, 1980). So, while the shrimp may be a
commensal on its anemone, it may simultaneously
be involved in a mutualistic relationship with
some of the fish in its community. Yet other
species of Periclimenes turn the usual
shrimp and anemone relationship onto its head.
Fautin and her coworkers have recently shown
that Periclimenes brevicarpalis, which
is found on the bulb-tipped anemone, Entacmaea
quadricolor, in the Indo-Pacific, grazes
on the anemone, eating its tentacles (Fautin,
et al., 1995; Guo, et al., 1996). So, in this
case, the shrimp is not a commensal but an ectoparasite.
transition from a commensal relationship to
true mutualism or, conversely, to a parasitic
relationship, appears to be easily accomplished,
and there are numerous examples of closely related
animals exhibiting these different aspects of
symbioses. If any reader wants to learn more
about some of these relationships, I recommend
he take a look at the very readable and well
illustrated book, Living Together In The
Sea, by Leon Zann, cited in the References.
Coral reefs and our coral reef aquaria contain
numerous examples of various aspects of symbioses,
as are illustrated in these images. Such relationships
are, however, common in all the world's seas
and may been seen on a visit to the sea shore.
D. G., C.-C. Guo and J.-S. Hwang. 1995. Costs
and benefits of the symbiosis between the anemone
shrimp Periclimenes brevicarpalis and
its host Entacmaea quadricolor. Marine
Ecology Progress Series. 129:77-84.
Guo, C. C., J. S. Hwang and D. G. Fautin. 1996.
Host selection by shrimps symbiotic with sea
anemones: A field survey and experimental laboratory
analysis. Journal of Experimental Marine Biology
and Ecology. 202:165-176.
M. B. and W. R. Brooks. 1997. Protection of
the symbiotic shrimps Periclimenes pedersoni,
P. yucatanicus, and Thor spec.
from fish predators by their host sea anemones.
In: den Hartog, J. C., L. P. van Ofwegen and
S. van der Spoel. Eds. Proceedings of the 6th
International Conference on Coelenterate Biology.
Nationaal Natuurhistorisch Museum. Leiden. pp.
L P. 1980. Living together in the sea.
T. F. H. Publications. Neptune NJ. 416 pp.
Text by Ronald L. Shimek,
Photos by Reef Central members.
Reefkeeping Magazine Reef Central, LLC-Copyright © 2008