Echinodermata
Olivia Johnson, Andrei Anashkin,
Heather Schlesier
http://www.dailywhatever.net/wp-content/uploads/2009/02/sea-cucumber-ga.jpg
Phylum
• Echinoderms are slow-moving animals that only
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live in salt water
A unique feature is the water vascular system
The phylum Echinodermata contains 6 major
classes: Asteroidea (sea stars), Ophiuroidea
(brittle stars), Echinoidea (sea urchins and sand
dollars), Crinoidea (sea lilies and feather stars),
Holothuroidea (sea cucumbers), and
Concentricycloidea (sea daises)
A Sea Star
Sample Animals
A Brittle Star
A Feather
Star
http://www.coral.org/files/images/7628-SeaStar.jpg
http://www.alaska-in-pictures.com/data/media/1/featherstar-pattern_6081.jpg
http://www.cartage.org.lb/en/themes/Sciences/Zoology/Animalclassification/Polygenetic/phylogenetictree/Echinodermata/
ophiuroidea.jpg
A Sea Urchin
A Sea Daisy
5
4
A Sea Cucumber
6
http://mollyobrown.files.wordpress.com/2009/11/red-sea-urchin.jpg
http://www.palaeos.org/images/thumb/5/5a/Acanthaster_planci.jpg/340px-Acanthaster_planci.jpg
http://www.reefseekers.com/PIXPAGES/Yap-Palau%20%2704/Grazing_sea_cucumber.jpg
Body Cavity
-are coelomates (posses a true coelom)
-coelom (body cavity): a fluid-filled space
that separates the digestive tract from the
outer body wall
-coelom is lined with mesoderm
Body Symmetry
• Adults have radial symmetry but it is a
secondary adaptation (many equal parts
radiate outward like the spokes of a
wheel)
• Echinoderm larvae have bilateral
symmetry (can be divided into two equal
halves)
Nervous System
• Echinoderms have a decentralized nervous
system.
• There is nervous tissue throughout the
echinoderm connected by central nerve
ring around its gut, but they have no real
brain.
• Some echinoderms instead have ganglia,
which are large clusters of nerve cells .
Water Vascular System
• Unique to echinoderms it is a network of
hydraulic canals branching into extensions
called tub feet that function in locomotion,
feeding, and gas exchange
Circulatory System
Digestive System
Excretory System
• Excretion can be preformed through
diffusion
• Contains an anus on the top of the central
disk
Locomotion/ Musculature
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•
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Made possible by the water vascular system and tube
feet
Sea Stars: undersurfaces of the arms have tube feet,
adheres firmly to rocks or creeps along slowly as the
tube feet extend, grip, contract, release, extend and
grip again.
– Made possible by a complex set of hydraulic and
muscular actions creating or releasing suction.
Brittle Stars: serpentine lashing of their arms
– Tube feet lack suckers so cannot grip
• Sea Urchins and Sand Dollars: don’t have arms, but
do have 5 rows of tube feet that function in slow
movement
– Also have muscles that pivot their long spines that aids in
movement
• Sea Lilies and Feather Stars: Sea lilies live attached
•
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to the substrate by a stalk; feather stars crawl about by
using their long flexible arms
Sea Cucumbers: have 5 rows of tube feet, some of the
tube feet around the mouth are developed as feeding
tentacles
Sea Daisies: they have armless bodies, not much is
known about them
Skeletal Type
• A thin skin covers an endoskeleton of hard
calcareous plates
• Most echinoderms are prickly from skeletal
bumps and spines
Sensory Structures/Features
• Regeneration allows some echinoderms to grow back
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lost arms or even full bodies
They have light and touch detecting cells but no sense
organs
– Starfish are an exception, they have eyespots on the
tip of each ray for light detection
They do not have heads or a brain, instead they have a
simple nervous system with a nerve net/ ring
Reproduction
•Sexual or asexual (regeneration)
•Sexual reproduction usually involves separate
male and female individuals that release their
gametes into the water
•Sea stars and some other echinoderms have the
ability to regenerate
•Sea stars can regrow lost arms, and one specific
genus can regrow an entire body from a single
arm
Gas Exchange
• Do not have a circulatory system
• Exchange gas through diffusion
• Diffusion is possible through the water
vascular system
• Structures: tube feet
Other Unique Stuff
• When feeding sea stars turn their
stomachs inside out and then secretes
juices to help it digest its prey
• Current sea lilies are very similar to fossils
of those that are 500 million years old:
their evolution has been very conservative
Which of the following do
echnodermata contain?
• Circulatory system
• Exoskeleton
• Endoskeleton
• Nervous system
What kind of symmetry do grown
echinodermata have?
• Bilateral
• Symmetrical
• Secondary radial