1. Echinoderms

2. Vocabulary
Make the vocab list yourself as you learn about Echinoderms!

3. Common Characteristics
Spiny skin
Endoskeleton
Radial Symmetry
Water Vascular
System

4. Water Vascular System Network of seawater- filled tubes
Functions: movement, help obtain food, circulation
One opening: madreporite
Water pathway: Madreporite, stone canal,
ring canal, radial canal, ampulla, tube foot
Know this!

5. Water Vascular System, Cont’d
How sea stars move:
Pump water into tube feet
These extend, attach to surface
Then water flows out of tube feet
They shorten, pulling sea star forward
Ampulla - round, muscular sac
Tube foot - suction cup, secretes mucus to stick to substrate
2 quick videos:

6. Symmetry Radial Why is phylum so advanced, then? (Next slide, please)
Necklace sea star

7. Symmetry
Bilaterally symmetrical larvae grows into radially symmetrical adult
1st echinoderms bilatera
Secondary radial symmetry

8. 5 Major Classes 1) Sea stars 2) Brittle stars
3) Sand dollars and sea urchins
4) Sea cucumbers
5) Sea lilies and feather stars (crinoids)

9. (1) Sea Stars
5-20 arms surround
central disk
Knobby Sea Star

10. Sunflower Sea Star

11. (2) Brittle Stars
Small with five long, thin arms; fragile

12. More Brittle Stars

13. (3) Sand Dollars Disc-shaped bodies Covered with tiny movable spines
Sediment feeders
This shows only “test”, or endoskeleton

14. and Sea Urchins Spherical bodies Sharp spines for defense
Grazers, sediment feeders or scavengers
“Aristotle’s lantern” - 5 part mouth
The Purple Sea Urchin is one of the sharp-spined urchin species. The spines are used as a means of defense against would-be predators. This urchin is deep purple in color, and grows to a diameter of about 4 inches. The are found along the western coast of the U.S. and Canada where they clink to depressions in the rocks during low tide.

15. Aristotle’s Lantern
You’re looking
at the mouth on
the oral side

16. Stronglyocentrotus droebachiensis
Longest scientific name in the world!

17. (4) Sea Cucumbers Think “sideways, elongated sea urchin”
5 rows of tube feet
Sticky tentacle-like tube feet surrounding mouth; eats organic debris in sand
Shoots thin tubules out anus when threatened - can eject entire digestive system!

18. (5) Sea lilies and Feather Stars
Most ancient group - few species left
Mouth on dorsal side
Sea Lilies
Sessile, have stalks
Feather Stars
Can creep or swim
crinoid swimming!

19. From here, we are talking about sea stars

20. Some have no anus
Very little released thru anus

21. Digestive System
Feed on clams, oysters, snails. . . Mouth is located on the ORAL side (underneath)
Stomach in central disk, digestive glands in arms
To eat: pry shell of prey open, evert stomach, digest prey in its shell, suck up soup
Small prey eaten whole, shells ejected through mouth
Note: “evert” means to turn inside out
Some have no anus
Very little released thru anus

22. Respiration Diffusion across skin of tube feet
Some also have tiny skin gills for diffusion
Some have no anus
Very little released thru anus

23. Excretion Diffusion across skin of tube feet and gills
Some have no anus
Very little released thru anus

24. Circulation
O2, metabolic wastes carried by water vascular system, but no true circulatory system
Some have no anus
Very little released thru anus

25. Nervous System No brain
Nerve ring circles mouth and connects with 5 radial nerves
Extensive sensory nerve network coordinates movement of spines/feet
Tip of arms have light-sensitive eyespot and nerves to sense food/chemicals
One arm leads, others follow

26. Reproductive System Most - dioecious
Two gonads in each arm, open directly to outside
External fertilization
Sea stars can regenerate arms
1st echinoderms bilatera
Secondary radial symmetry