1. Starfishes, sea urchins, sea cucumbers
Phylum Echinodermata
Starfishes, sea urchins, sea cucumbers

2. General Characteristics
Echino- (spiny) derm (skin)
Exclusively Marine – usually shallow, coastal waters and ocean trenches
Unsegmented Body
Larvae are free-swimming and bilaterally symmetrical
Adults become bottom-dwelling with radial symmetry
Most have five radii or multiples of five which is known as pentaradial symmetry
Unique water vascular system

3. General Characteristics cont.
First phylum with endoskeleton (with exceptions)
With dermal calcium plates (calcareous ossicles)
Some with protruding spines or spicules
Complete Digestive System
No defined circulatory, respiratory, or excretory systems (no kidneys)
Instead, have tiny tube feet that aid in movement, feeding, respiration, and excretion
Distinct males and females reproduce sexually and/or asexually
Have a nervous system but no head or brain.

4. Class Asteroidea (“star-like”)
Examples: Sea Stars
Found all over coastal shores around the world
Use tube feet to pry open the shells of oysters, clams, and other sea food that are used by people 4

5. Body Plan of the Sea Star
Oral surface: mouth located on the underside of the body
Aboral surface: top of the body (anus is located here)
Ossicles: sharp protective spines made of calcium plates, covered with thin epidermal layer (this is what makes it spiny)
Pedicellariae: tiny forceps that camouflage or clean the body surface
(white structures) 5

6. External Anatomy
Aboral Surface
Oral Surface

7. Internal Anatomy

8. Asteroidea – Sea Star

9. Class Ophiuroidea (“snakelike”)
Examples: Basket Stars & Brittle Stars
Largest echinoderm class
Primarily reside under stones & in crevices and holes of coral reefs
Thin brittle arms that break off & regenerate themselves quickly
Feed by raking food off the ocean floor with their arms and bottom of tube feet
Trap food with mucous strands between their spines. 9

10. Ophiuroidea (“snakelike”)
No anus
Madreporite on oral surface rather than aboral surface
No suckers on tube feet, no ampullae (have a valve to control water pressure)
No pedicellariae
Gametes (sperm or eggs) released through bursal slits 10

11. Brittle star anatomy

12. Ophiurodea – Brittle Star, Basket Star

13. Class Echinoidea (“hedgehoglike”)
Examples: Sand Dollars and Sea Urchins
Sand Dollar:
Live along seacoasts & sandy areas
Flat, round shape bodies
Adapted for shallow burrowing
Short spines allow for movement (also aid in burrowing & cleaning their bodies)
Use tubes to filter food out of water 13

14. Class Echinoidea Sea Urchins:
Test: rigid endoskeleton that the internal organs are compacted in
Aristotle’s lantern: complex jaw-like mechanism that is used to grind their food
Tube feet allow for movement
Barbs on their long spines are sometimes venomous provide protection from predators 14

15. Anatomy of a Sea Urchin

16. Aristotle’s Lantern – Sea Urchin

17. Echinoidea – Sea Urchin, Sand Dollar

18. Class Holothuroidea Example: Sea cucumbers Bodies are soft
Skeletal system reduced or absent
No spines or pedicellariae
Feed by sweeping up sediment from the water with tentacles around mouth
Protect themselves by ejecting internal organs through the anus.
Lost parts are later regenerated which is a process called evisceration. 18

19. Sea Cucumber Anatomy

20. Holothuroidea – Sea Cucumber

21. Class Crinoidea (“lilylike”)
Examples: Sea lilies and Feather stars
Sessile
They have long stalks that attach to rocks or to the ocean floor
Feather stars eventually detach themselves
Sticky tube feet that are at the end of each arm catch food and serve as a respiratory surface. 21

22. Crinoidea – Sea Feathers, Sea Lily

23. Class Concentricycloidea
Examples: Sea Daisy
Less than 1 cm in diameter (so extremely small)
Disc-shaped with no arms
Tube feet are located around the disc-shaped center
Looks very much like a daisy 23

24. Class Concentricycloidea
Example:
Sea Daisy

25. Other Structures 25

26. Water-Vascular System
Hydrostatic pressure permits movement
Path of water in the Water-Vascular System
Enters sieve plate
Passes through stone canal
Traces a path from the ring canal encircling mouth to 5 radial canals that extend to each arm
Ampulla: bulblike sac that each foot connects to
Tube feet contract so that water enters; this allows them to be able to suction onto the surface of slippery rocks 26

28. Other Body Parts
Fluid in coelom bathes organs to distribute nutrients & oxygen
Skin gills: protect coelom lining; gases are exchanged
Nerve ring: surrounds mouth & branches off into nerve cords in each arm.
Eyespots: end of each arm that responds to light 28

29. Reproduction Sexually reproduces with each arm producing sperm or egg
Releases sperm or egg into the water for fertilization (oviparous fertilization)
Bipinnaria: a fertilized eggs develops into a free-swimming larva
settles in the bottom and develops into an adult through metamorphosis
Asexually reproduces by regenerating lost parts 29

30. Larval Echinoderms with bilateral symmetry