What traits do you think
the following organisms all
share in common?
Use the defining characteristics of fish that you just
learned to help guide you.
Sea star
Sea urchin
Sea cucumber
Sand dollar
Brittle star
Invertebrates:
• Kingdom: Animalia
• Phylum: ????????????????
We are now going to look at several other phyla
as we move through the end of the course that
are still grouped in the animal kingdom, but lack
a spinal chord (invertebrates).
Echinoderms – Stars of the Sea
-Kingdom: Animalia
-Phylum: Echinodermata
Echino = spiny
Derm = skin
Echinoderms – Stars of the Sea
-At first glance, it may be impossible to group the
various forms of echinoderms together.
-Examples: Sea stars, sea urchins, crinoids, brittle
stars, sand dollars, sea cucumbers.
-They can all look extremely different, but with a
closer look they actually possess many similarities.
Echinoderms – Stars of the Sea
-The major characteristic that all echinoderms have in common:
1) Body has no segments (this is a common distinguishing
characteristic for any invertebrate)
Echinoderms – Stars of the Sea
-The major characteristic that all echinoderms have in common:
2) Radial symmetry – divided into 5 parts
1
5
2
4
3
•Every arm has an equal
share of the animal’s
systems!
Echinoderms – Stars of the Sea
3) Water vascular system – water suction system for moving
around/self-defense (almost like hydraulics)
tube feet
*Most have
tube feet
pedicellaria
Echinoderms – Stars of the Sea
4) Ossicles (a.k.a. test) – a solid “skeleton-like” structure that
makes echinoderms rigid.
*They are made of calcium carbonate (like sea
shells) and have different shapes for each class of
echinoderm.
Provides stability and protection.
Echinoderms – Stars of the Sea
5) Dermal Branchia – Respiration/gas exchange. These are
small soft lumps on the exterior of the body that absorb
oxygen for respiration.
Oxygen from water
Echinoderms – Stars of the Sea
Reproduction – can be asexual or sexual.
*asexual = regeneration of limbs
•Every arm has an equal
share of the animal’s
systems!!!!
•They can regenerate
arms!!!
*Sexual = free
spawning
Echinoderms – Stars of the Sea
-Sea stars actually have an “eye” at the
end of each arm called an ocellus.
-It allows them to recognize light and dark areas, not actually see
figures.
-Their other main senses are taste (with mouth parts/chemical
receptors) and feel (with nerves near tube feet)
-So closely related to chordates (us) because their development stages are very
similar to ours!
All other
marine
invertebrates
Us and
echinoderms
1)We are both dueterostomes (first embryonic opening, or blastopore, becomes
anus).
2)In all other sea organisms, it becomes the mouth (protostomes)
3)We both have bilateral symmetry during developmental stages.
-Thus, sea cucumbers are our closest relative in the sea (other than the
vertebrates)
-Echinoderms are often times used as an “indicator species” in
marine environments.
Army of sea stars
-They play an important role in shallow water ecosystems, so
their presence or absence usually tells scientists how healthy
the ecosystem is.
A healthy balance of
these 2 pictures
represents a healthy
ecosystem.
An overgrowth of kelp means
the water is not healthy enough
to support urchins. (urchins eat
the kelp)
An area with no kelp means
the water is healthy, but
something is wrong with the
otter/sea star population.
(otters/stars eat urchins)
SKETCH 1 – Label the arms,
ocelli, and madreporite. Also,
describe function of the
madreporite.
Eyespot
(ocellus)
Tube feet
SKETCH 2 – Draw the ventral side of the
starfish, including the labels above.
SKETCH 3 – Open the starfish on
the dorsal side. Label the circled
parts of the internal anatomy.
SKETCH 4 – Draw a picture of
JUST the water vascular system.
Label all circled parts of the
anatomy. Explain the function of
the water vascular system below
the sketch.
Analysis
• List 5 characteristics of the starfish that you
expect to see tomorrow during the sea urchin
dissection.
Move using extended
tube feet
Sea Urchin
Spines can
cause painful,
infected stings
(few are
venomous)
Gonads are a delicacy
in some cultures.
Eat using mouth parts
called “Aristotle’s Lantern”
SKETCH 1 – EXTERNAL VENTRAL SIDE (you will see
the mouth, spines, and pedicellaria)
SKETCH 2 –
EXTERNAL
DORSAL SIDE
(you will see the
anus and
madreporite)
SKETCH 3 – carefully cut an opening on the side of the
urchin. (be careful cutting around the sharp spines). Once
you open the urchin, first draw the digestive and
reproductive organs.
-Stomach/Intestines (brown on the diagram)
-Reproductive glands (pink on the diagram)
SKETCH 4 – Now draw the water vascular system (blue on the diagram).
Water travels in through the madreporite, travels down through the stone
canal into the ring canal, and finally gets moved through each of the 5 radial
canals where water is pumped into and out of tube feet to move the urchin
along the sea floor.
SKETCH 5 – Aristotle’s Lantern
With the urchin open, remove the solid tooth-like organ directly above
the mouth. This is actually 5 separate teeth surrounded by muscle
that the urchin uses to chew. This organ is known as Aristotle’s
Lantern. Draw the mass.
List 5 characteristics of
sea urchins that you
expect to see on Tuesday
in the sea cucumbers.
Sea Cucumber
Radial Symmetry
-Sea cucumbers are essentially elongated urchins
without the spines.
-The are widely dispersed and have been found in
every area of the ocean floor.
-They can extrude gonads and other internal organs
through their anus as a self defense mechanism.
(allow predator to eat these organs or sometimes
they are sticky and trap the predator to avoid being
eaten).
Over 2,500 species have
been discovered with a
huge variety of colors,
sizes and appendages.
Sketch 1 – External anatomy. Sea cucumbers are just
elongated sea urchins without the spines. You will see tube
feet for transport just like the urchin. They have a continuous
digestive system with a mouth inside a group of tentacles and
an anus at the other end.
Find the madreporite, where water is pulled into the water
vascular system.
Madreporite
The tentacles are just modified tube feet to help snatch small prey.
Sketch 2 –
reproductive
These are the
organs that the
cucumbers can
push out to
distract or trap
potential
predators.
The gonad will take up more space than the
picture displays. Label the gonads and then
remove them to reveal the other internal
organs.
Label the pharynx (throat), stomach, intestines,
and anus
Sketch 4
Water
vascular
system
Behind the reproductive and digestive organs you will find the water vascular
system. As with the other echinoderms, label the madreporite, stone canal,
ring canal, radial canals, and tube feet.
There was no mention of any ossicle (skeleton) in this echinoderm dissection.
They do have an ossicle, how do you think it might be incoroporated into their
body structure?
It is made of thousands of tiny individual
microscopic parts.