Download The phrase symbiotic relationship simply refers to a close ecological

Symbiosis
The phrase symbiotic relationship
simply refers to a close ecological
relationship between two different
species. These relationships differ
along a spectrum from positive to
negative interactions. If both
species benefit from the
interaction, the relationship is
Figure 1. Coral reef
considered to be a mutualism.
When one species benefits and
the other is not impacted, the relationship is
considered to be a commensalism. When
one species benefits and the other species
is harmed, the relationship is considered to
be either parasitic or predatory or
herbivorous. If both species are impacted
negatively through a competition over limited
resources, the relationship is considered to
be competitive.i
Symbiotic relationships can vary in intensity.
If the organisms are dependent upon each
other, the relationship is termed obligate.
However, when the organisms can survive with or without this
relationship, it is termed facultative.
Figure 2. Coral
feeding
Symbiotic relationships come in many forms that span the tree of
life, and they can be found in all ecosystems, from terrestrial to
aquatic. One of the most diverse ecosystems which easily
contains examples of each relationship type can be found in the
ocean, specifically coral reefs.
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Coral reefs are considered to
be among the most
ecologically diverse systems
in the world. Coral reefs are
created from small coral
animals which are classified in
the cnidarian group. As
adults, corals are stationary
and are considered sessile.
They have small soft bodies,
each protected by a hard
Figure 3. Aerial view of coral reef
calcium carbonate skeletal
structure that is secreted continuously at the base of the body
over the animal’s lifetime.ii As coral feed, they use their tentacles
to reach out and capture small plankton and fish. Once a potential
threat swims by, the coral retreat into their protective skeleton.
Coral animals live in communities, and once old coral animals die
off and new ones settle on top of the dead skeletons, the coral
reef structures will build up substantially over time.iii
Corals are not the only animals that
live within their reef structures. Many
species of fish, fungi, sea turtles,
algae, sponges, oysters, clams,
shrimp, crabs, sea stars, urchins, and
even other cnidarians
like jellyfish and sea
anemones all call
Figure 4. Clown fish and
these reefs home.iv
anemone
With such a diverse
assemblage of organisms, it is easy to see how a Figure 5. Sea
variety of ecological interactions would evolve
spider
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over time.
In the coral reef system, a classic example of a mutualistic
relationship exists between clown fish and sea anemones. Made
famous by Pixar’s movie, Finding Nemo, clown fish often hide
within the stinging tentacles of sea anemones. The clown fish get
protection, while they also scare off potential predatory fish of the
anemone and therefore provide protection for their protectors.
A commensalism exists commonly in the coral reef between glass
shrimp and chocolate chip sea stars. Glass shrimp, as they are
named, are almost completely transparent. To hide from
predators, they often hop on the back of a chocolate chip sea star
for camouflage, while the sea star is completely unaffected.v
Parasitic interactions are common in any ecosystem, and the
coral reef is no exception. Sea spiders are considered parasites
to table coral. Sea spiders often seek protection and will pierce
the body of the coral (called the polyp) and live inside them.
Herbivory is illustrated in coral reefs by several species, including
the long-spined sea urchin as well as herbivorous fish species.
These urchins and fish will graze on algae that are commonly
found throughout the reef, which will essentially take over and
negatively impact the community if populations are not kept in
check.vi
Predation is also common in these reef
communities, and a classic example
involves the barracuda fish and
the parrotfish. Barracuda fish are fierce
predators and regularly seek out prey such
as the colorful herbivorous parrotfish.
Another example, which reveals some
Figure 6.
Barracuda fish
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complexity in the coral reef, involves the saddled
butterflyfish and the sea anemone. We mentioned
earlier that clownfish protect the anemone against
their predator, which happens to be a saddled
butterflyfish!vii
Figure 7.
Saddled
butterflyfish
There are many more types of interactions within
not only the coral reef community but in
communities all over the world. However, these
examples give a glimpse of the complexity that can
arise over a long and complex evolutionary history!
i
Marietta College, “Symbiosis,” n.d.,
http://www.marietta.edu/~biol/biomes/symbiosis.htm. ii University of Michigan,
“Ecological Communities: Networks of Interacting Species,” 2008,
http://www.globalchange.umich.edu/globalchange1/current/lectures/ecol_com/ec
ol_com.html.
ii
Environmental Protection Agency (EPA), “Coral Reef Protection: What Are
Coral Reefs?” n.d., http://water.epa.gov/type/oceb/habitat/coral_index.cfm.
iii
Ibid.
iv
Ibid.
v
Canisius College, Canisius Ambassadors for Conservation, “Mutualism,” n.d.,
http://www.conservenature.org/learn_about_wildlife/great_barrier_reef/mutualism
.htm.
vi
The Nature Conservancy, “Coral Reefs,” 2012,
http://www.reefresilience.org/Toolkit_Coral/C3a1_Herbivory.html.
vii
The Nature Conservancy, “Coral Reefs,” 2012,
http://www.reefresilience.org/Toolkit_Coral/C3a1_Herbivory.html.
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Pictures: Figure 1. Coral Reef
http://upload.wikimedia.org/wikipedia/commons/d/d0/Coral_reef_a
t_palmyra.jpg
Figure 2. Coral Feeding
http://upload.wikimedia.org/wikipedia/commons/9/90/Lobophyton_
%28soft_coral %29_with_extended_polyps.jpg
Figure 3. Aerial View Coral Reef
http://commons.wikimedia.org/wiki/File:Coral_Reef_aerial.png
Figure 4. Clown fish and Anemone
http://commons.wikimedia.org/wiki/File:Clown_fish_amphiprion.jp
g
Figure 5. Sea Spider
http://upload.wikimedia.org/wikipedia/commons/2/27/Sea_spider.j
pg
Figure 6. Barracuda Fish
http://commons.wikimedia.org/wiki/File:Barracuda(kok).jpg
Figure 7. Saddled Butterflyfish
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http://upload.wikimedia.org/wikipedia/commons/1/16/Saddle_Butt
erflyfish_1.jpg
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