Bellwork: 11/19/2013
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Many students seemed to mix up Porifera &
Cnidaria
Make sure to avoid that on the next unit since
it includes:
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Echinoderms
Bivalves
Cephalopods
Gastropods
Mollusks
Crustaceans
Echinoderms
Phylum Echindermata
•Share common features with chordates
•Radial Symmetry
•Usually slow moving or sessile
•Possess a thick calcium plate endoskeleton
surrounded by a thin skin layer
•Possess a unique Water Vascular System, which
continues throughout animal and extends into
extensions called Tube Feet.
- Functions for locomotion, feeding, & gas
exchange.
Water vascular system
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4
A separate coelom is
used with
interconnecting fluid
filled tubes and canals
A ring canal circles the
mouth and gives off 5
radial canals
The radial canal is
exposed and runs along
the ambulacral groove
Phylum Echinodermata
Water Vascular System
Phylum Echinodermata
5
Tube Feet
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6
The ampullae is a
small ball that sits
above the tube foot
Contraction and
expansion of the
ampulla accomplishes
movement
Phylum Echinodermata
Sea Stars
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Usually have 5 (or
multiple of 5) arms
radiating from central
disk
Tube feet located
underneath each arm
used for locomotion &
grasping prey. Operate
by hydraulic
principles.
Echinoderms Skeleton
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Have an internal skeleton of
calcium carbonate
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8
Ossicles vary in size
and structure and are
manufactured by
specialized cells
Phylum Echinodermata
Anatomy of a Sea Star
B: Ambulacral
Groove
F: Arm
E
C
A
10
Feeding
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Feed on mollusks
by pulling shells
apart and extending
stomach outside the
mouth into the
bivalve. The bivalve
is digested within
it's shell. The sea
star than re-ingests
its stomach
Reproduction
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Can reproduce
sexually by releasing
sperm and egg.
They are NOT
hemaphrodites
Can reproduce by
regeneration
Regeneration
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13
Many species autotomize,
leaving predators with a
nutritious souvenir while
they escape
Most spp. can regenerate
from fragments that
include the disk
Phylum Echinodermata
Sea Stars
Brittle Stars
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Distinct central
disks with long
tube-like arms
Lack suckers
Move by serpentine
motion of their
arms
Brittle Stars vs Sea Star
Movement
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Sea Stars use their
tube feet to crawl
across the sea floor
Brittle Stars use
one of their legs as
a lead and pull
themselves across
the sea floor
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Sea star
locomotion
Brittle Star
Locomotion
Brittle Star
Sea urchins & sand dollars
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Lack arms, but possess tube feet
Many species of urchins possess poisonous
spines used for defense
Sand Dollar
Sea Urchin
Sea Cucumbers
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Soft body
with reduced
structure
Tentacles
near mouth
Respiratory
tree
Sea Cucumbers
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Are elongated
along oralanal axis
Lack spines
and have
reduced
endoskeleton.
Do possess
tube feet and
water vascular
system
Expels its
insides as a
defense
mechanism
Sea Cucumber
Echinoderm Lab:
Groups of 4 or less
Station #1 – Sand-Sifting Sea Star
1)
Flip the sea star onto its dorsal side &
observe:
a)
b)
2)
Draw or describe how the sea star flips itself back
over.
What sensory cells are involved in keeping the sea
star upright?
Place the sea star upside down the dissection
microscope.
Station #1 – Sand-Sifting Sea Star
3) Observe, sketch, and label the following
regions: center of the sea star, middle of an arm,
terminal end of the arm.
Label if present in each sketch:
o Mouth
o Tube feet
o Abulacral groove
o Spines
o Sensory Tentacles
Station #2 – Tube Feet Prepared Slide
1)
Observe & sketch the prepared slide on both
the low & medium objectives.
a)
b)
c)
d)
e)
Describe the shape/texture of the ectoderm on the
tube feet.
Why are the tube feet hollow?
What is the name of the tissue that the tube feet
are connected to?
Why does this tissue appear to have empty
pockets.
Aside from locomotion & feeding, what other job
do tube feet perform? What feature of the tube
feet allows this to be possible?
Station #3 – Amputated Arm & Crosssection
1)
Examine the cross-section under the dissection
microscope.
Sketch the cross-section
Label the following:
a)
b)
•
•
•
•
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Digestive gland/pore
Ambulacral groove
Tube feet
Ampulla
Water vascular pore
Station #4 – Brittle/Serpent Sea Star
1)
Remove the brittle star/serpent sea star from
the container & place it on the table.
a)
b)
c)
2)
How does it move?
How does a sea star move in comparison?
What are the advantages & disadvantages of both
types of movement?
Observe & sketch the central disk of the
brittle/serpent sea star.
Station #4 – Brittle/Serpent Sea Star
3. Observe & sketch the amputated brittle sea
star leg under the dissection microscope & the
cross-section under the standard microscope.
a)
How is this arm different than the arms of a
standard sea star?
Station #5 – Sea Urchin
1.
Using your finger, gently poke one of the
spines on the sea urchin.
a)
b)
2.
What is its response?
What receptors are involved in this detection?
Using the urchin with shorter spines, gently
flip the urchin over.
a)
b)
c)
How does it flip itself over?
Is this a faster or slower process than with the sea
star?
Why do sea urchins have tube feet that are much
longer than those found on any other echinoderm?
Station #5 – Sea Urchin
3.
Observe the long-spined urchin.
a)
b)
What are the white spots on the dorsal portion of
the animal?
What is the green (orange?, red?, sorry…I’m not
sure what color it is) anatomical feature found in
the very center of the dorsal side?
Station #6 – Sea Cucumber
1.
2.
Observe & sketch the sea cucumber under the
dissection microscope.
Label the tube feet, respiratory tree, and
tentacles.
a)
b)
Describe the texture of this animal in comparison
to the other echinoderms.
While considering the relatively low number of
tube feet found on this organism in comparison to
other echinoderms, what functions would the sea
cucumber lack & what additional anatomical
feature(s) can be found to address these
deficiencies?