Phylum Echinodermata

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Phylum Echinodermata
spiny skin
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Echinoderm
Characteristics
1. radial symmetry
2. endoskeleton
3. spiny skin
4. water vascular system
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All echinoderms have radial symmetry.
feather star
starfish
brittle star
sand dollar
sea cucumber
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They start out, however, with bilateral symmetry.
starfish larvae
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All echinoderms also go through deuterostome
development (this means the blastopore becomes
the anus).
two body openings
Note the mouth is on the ventral (oral) surface
and the anus is on the dorsal (aboral) surface.
This is true for most echinoderms.
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The skeleton of the echinoderm is internal
because it is covered with skin.
skeletal remains
with skin (alive)
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Echinoderms are considered to be related to
vertebrates because of these three
characteristics.
1. bilateral larvae
2. deuterostome development
3. internal skeleton
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Echinoderms have a spiny skin. The spines vary in
length.
very long spines
very short spines
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Most echinoderms use a water vascular system
similar to this one.
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Tube Feet - used for movement, respiration and
feeding.
tube feet
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Close-up of Tube Feet
tube feet
They are on the ventral surface.
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Echinoderm Classification
Kingdom
Animalia
Phylum
Echinodermata
Class
starfish -
Asteroidea
sea lilies -
Crinoidea
brittle stars -
Ophiuroidea
sea urchins -
Echinoidea
sea cucumbers -
Holothuroidea
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Class Asteroidea
starfish
aster means star
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Starfish Characteristics

• most have 5 rays (arms)

• rays are broad at base

• all live in the ocean

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A Larval Starfish
Even at this stage you can see 5 rays developing.
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Starfish come in many colors.
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Starfish are also called sea stars.
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Starfish usually have 5 arms
called rays.
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Some have more than 5 rays.
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For some, the rays are fat or
tissue fills in the space.
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Starfish have spines.
Some are large, some are small.
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Starfish eat other animals.
eating a clam
eating coral
spines
eating a
sea urchin
mouth
ventral surface
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Feeding
Starfish use their tube feet to pry open bivalves
(a favorite food).
stomach
ventral surface
They extend their stomach out their mouth to
digest the bivalve.
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Starfish have been around
a long time!
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Although they cant be seen, starfish have
eyespots at the ends of their rays.
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Starfish Body Structures
anus
stomach
madreporite plate
tube feet
stone canal
ampulla
digestive glands
radial canal
ring canal
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Class Crinoidea
sea lilies
and
feather stars
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Crinoid Characteristics
Sea Lilies

• sessile with a stalk

Feather Stars

• swim with feathery rays

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Many crinoids look like flowers.
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Sea Lilies
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stalk
sea lilies have a stalk
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the stalk makes it look like a lily
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feather stars have no stalk
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Feather star on a rock.
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Red Sea Feather
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The Pink Feather Star
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Feather Star with many rays
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A feather star eating a starfish.
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more feather stars
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Class Ophiuroidea
brittle stars
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Brittle Star
Characteristics

• rays are very thin

• rays are very brittle

• rays used for movement

(not tube feet)
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long thin rays
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central disc
anus in middle of disc
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Black Brittle Star
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brittle star with long spines
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more brittle stars
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Class
Echinoidea
sea urchins
and
sand dollars
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Sea Urchin
Characteristics

• shaped like a globe

• long, hard spines

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sea urchin
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many spines
sometimes they are poisonous
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some have small spines
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more sea urchins
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Sand Dollar
Characteristics

• shaped like a disc

• hairlike spines

• no space between rays

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space between rays is filled in
ray
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sand dollar
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one with an unusual pattern
sand dollar
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more sand dollars
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Class
Holothuroidea
sea cucumber
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Sea Cucumber
Characteristics

• shaped like a cucumber

• eject insides out anus

• leathery skin

• move with tube feet/tentacles

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sea cucumber
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another cucumber
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some have large spines
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sea
cucumbers
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The
End