ECHINODERMS
The Amazing Species of the Phylum
Echinodermata
Of all the phylum of
organisms,
echinoderms are
one of the most
interesting. People
often find
fascination in them
due the
mysteriousness of the creature and the beauty of the
environment of which they inhabit. Here you will find a
brief description of both, and hopefully learn something
about these magnificent creatures.
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Species within the
Phylum
The phylum is
Echinodermata making
the creatures within it
echinoderms. The
literal translation of the
Greek word,
Echinodermata, is “spiny
skin.” There are 6,000
species of the spiny
skinned organisms. It is
interesting to note that
over twice as many
more of the species are
now extinct than are currently existing today, at about 13,000.
There are six classes of species within the phylum. Some of the
most well-known species within the phylum are the sea urchin,
sand dollar, sea cucumbers, sea lilies, brittle stars, basket stars,
and of course the starfish. Here, is a more thorough list of the
species.
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Location
One fact about echinoderms could cause some jealousy for us
humans. They only reside in some of the most beautiful places in
the world. All echinoderms live in the sea and can be found in
marine environments several places around the world. With the
massive amount of species in the phylum, echinoderms are the
largest group with no freshwater or land representatives. A vast
amount of echinoderms are suited perfectly for life in the coral
reef.
General Characteristics
While the different species within the phylum may look nothing
alike, they do all share some similar characteristics in body type
and
functionality.
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Echinoderms
generally
have 5 or more arms extending from a central location
giving them radial symmetry.
Notice the radial
symmetry in
which the 5 arms
of this starfish
extend from the
center of its
body.
This is referred to as
pentamerous radial symmetry. It is interesting to note
that radial symmetry is developed and not inherent.
Most
echinoderms, including starfish, are bilaterally symmetrical in their
immature phases. It is not until adulthood that they are radially
symmetrical. Another characteristic that exists in all echinoderms
is their water vascular system. This, in conjunction with tube feet
on the bottom of the organism, allows for movement.
Some
echinoderms do not take advantage of the ability to move, but all
have the mechanisms necessary to be mobile. One of the more
shocking characteristics of all echinoderms is that none of them
possess a brain. As humans, it is difficult for us to fathom how any
creature can function without a brain. This is true especially due to
the fact that echinoderms move, react, sense, and prey on other
organisms. How does a sea star function without a brain? How
does it coordinate its arm movements and sense light with the
“eyespots” if there are no brain cells to process or use the
information? The link provided gives a brief, but accurate answer
to those questions.
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Eating Habits
There is not one common link between echinoderms in terms of
their dieting habits. Some are carnivorous predators, others are
scavengers, and some simply feed on plankton in the marine
environment. Many echinoderms have hardened parts in the
mouth that can act as teeth to help them capture prey. One of the
most fascinating things seen in this phylum comes from the sea
stars. They do not have any teeth like structure. Instead, their
stomach actually comes out of their body and envelops the pray.
They then secrete digestive enzymes to liquefy the tissue of the
prey.
Impact on Humans
Along with the vast role
echinoderms play in their
natural environment, they
also have a positive
impact in the human
realm. It is possible to
produce large amounts of echinoderms in a lab setting. For this
reason, they have been widely studied and led to advancement of
knowledge in the area of animal fertilization and development.
Also, some echinoderms have important economic roles. One
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example of this involves sea urchins. More specifically, sea urchin
eggs are edible and are often sold in sushi restaurants around the
globe.
References
Bird, J. 2007. “Echinodermata: The Spiny Animals!”. Accessed February
23, 2012
athttp://www.oceanicresearch.org/education/wonders/echinoderm.ht
ml
Coral Reef Echinoderms. 2010.
Flower Garden Banks National Marine Sanctuary. Echinoderm Species.
Accessed March 27 at
http://flowergarden.noaa.gov/about/echinodermlist.html
Mulcrone, R. 2005. "Echinodermata" (On-line), Animal Diversity Web.
Accessed February 23, 2012 at
http://animaldiversity.ummz.umich.edu/site/accounts/information/Echi
nodermata.html
Penryn, Kevin. 2008. Article accessed March 28 at
http://www.wonderquest.com/sea-stars-nights-space-radiation.htm
Sushi Items- Uni. What is Uni? Article accessed March 30 2012
athttp://www.sushifaq.com/sushi-sashimi-info/sushi-itemprofiles/sushi-items-uni-sea-urchin/
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Zelnio, Kevin. 2012. Deep Sea News. Article accessed March 29
at http://deepseanews.com/2012/03/veins-of-water-the-evolutionof-the-echinoderm-water-vascular-system/
Zubi, T. 2010. “Echinoderms”. Accessed February 23, 2012 at
http://www.starfish.ch/reef/echinoderms.html.
http://www.oceaninn.com/the-nature-preserve/echinoderms/
http://www.fossilmuseum.net/Tree_of_Life/PhylumEchinodermata.htm
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