14. Phylum Echinodermata Notes

1. Phylum
Echinodermata
Kingdom Animalia
Phylum Echinodermata
Class Asteroidea
Class Ophiuroidea
Class Echinoidea
Class Holothuroidea

2. Echinoderms:
Name means
“spiny skin”
Sea stars, sea
cucumbers, sea
urchins, etc.
 All marine
 All found on the
bottom of the
sea

3. General Characteristics:
Lack a head
Two sides (oral
& aboral)

4. Symmetry -
Bilateral Symmetry -
Common of free moving
organisms
Radial Symmetry -
Common of sessile (non-
moving,/attached
Free moving and radial
symmetry
Pentaradial Symmetry –
body radially symmetrical
in 5 parts or multiples of 5
Echinodermata Symmetry -

5. Endoskeleton:
 Internal skeleton found within the tissues
 It is always covered by a thin layer of tissue
 Spines and bumps give reference to their name
which means “spiny-skinned”

6. Water Vascular System
 A network of
fluid filled canals
 Used for
locomotion, food
& waste
transport, and
respiration

7. Water Vascular System:

8. Water vascular system
 Water enters through the
madreporite
 Water is then separated into five
radial canals made of double rows of
ampullae
Ampullae are connected to sucker-
like podia, the whole thing is called a
tube foot
Contraction of the ampullae causes
the podia to move, thus overall
locomotion

9. Dermal Branchiae
 Soft bumps on the body that
absorb oxygen from the water

10. Digestive System:
 Sea and brittle
stars can evert a
portion of their
stomach out of
there mouth to
engulf food
 Digestive
enzymes located in
glands that extend
into the arms

11. Digestive System:
 Sea urchins have
a longer coiled
intestine to allow
time for the
digestion of plant
material
Sea cucumbers
have a similar
section to absorb
nutrients from the
sediment it ingests

12. Nervous System:
 Limited
knowledge on
this aspect
except for the
presence of a
nerve net
 Ocelli –
microscopic
pigment spots on
sea stars that
can detect light
and dark

13. Regeneration/Autonomy:
 The ability to
grow lost or
damaged body
parts
 Some times a
severed arm can
grow into a new
organism if 1/5 of
the central disc
is present

14. Class Asteroidea
 Includes: sea
stars or starfish
Most have 5 arms
from a central disk,
though can have
up to 50
Each arm carries
an equal share of
organ systems

15. Class Asteroidea
 Ambulacral
grooves
contain the
tube feet on
the arms

16. Class Asteroidea
Pedicellariae
Tiny pincer-like
organs on the aboral
side keep the surface
clean
 Most sea stars are
predators of bivalves,
snails, or other
attached or slow
moving animals

17. Class Ophiuroidea
 Includes: Brittle
Stars
 Legs proportionally
longer and thinner
than sea starts
 Allows for better
movement
 Organs in central
disc
 Tube feet lack
suckers

18. Class Ophiuroidea
 Eat organic
matter and small
animals they find
on the bottom
 Passed from
tube foot to tube
foot till it reaches
the mouth

19. Class Echinoidea
 Includes: Sea
Urchins & Sand
Dollars
 Body structure
forms a round, rigid
body with movable
spins and
pedicellarie
 Locomotion
achieved by
movable spines

20. Class Echinoidea
 Body plan of sea
stars repeated by
moving arms upward
and connecting them
at the tips
 Mouth is on the
bottom, anus on the
top
 Spines: sharp, hollow
and sometime contain
venom

21. Plates:
10 plates
Alternating abulacral
(have openings for
tube feet) and
interambulacral
(bumps for spines)

22. Class Echinoidea
 The mouth has an
intricate system of
jaws and muscles
called Aristotle’s
Latern
 Used to bite off
algae and other
bits of food from
the bottom

23. Class Echinoidea
 Heart Urchins
and Sand Dollars
are adapted for
the soft bottom
of the ocean
 Flat bodies and
short spines

25. Class Holothuroidea
 Sea Cucumbers
 Similar body plan
to a sea urchin,
just stretched out
from mouth to anus
 Lies on sides, oral
and aboral
surfaces are at the
ends

26. Class Holothuroidea
 Most have five rows
of tube foot that run
mouth to anus
 Some excrete toxic
substance as defense
mechanism
 Some expulse gut
and other internal
organs out of the
mouth or anus, called
evisceration
 Believe that they
grow the organs back