1. Phylum Echinodermata There are more than 5000 species of Echinoderms.
Echinoderms have spiny skins.

2. Defining Characteristics
A complex series of fluid filled canals with numerous flexible feeding and locomotory appendages
5 pointed radial symmetry in adult
Exclusively Marine
Body unsegmented
Larvae bilaterally symmetrical
With unique water vascular system
Digestive system complete
Respiration by dermal branchae, tube feet, or respiratory tree
No kidneys
Dioecious
Locomotion by tube feet, and/or arms

3. External Anatomy

4. Larval Echinoderms showing bilateral symmetry

5. Echinoderms Skeleton
Have an internal skeleton of calcium carbonate
Ossicles vary in size and structure and are manufactured by specialized cells

6. Water vascular system
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

7. Water Vascular System

8. Water Vascular System

9. Tube Feet The ampullae is a small ball that sits above the tube foot
Contraction and expansion of the ampulla accomplishes movement
They also have a water vascular system that enables them to store water in their tube feet so they can survive while the tide is out.

10. Mutable Connective Tissue
Another unique Echinodermata characteristic is the presence of mutable connective tissue

11. Higher Classification Echinodermata
Class Asteroidea – sea stars
Class Ophiuroidea – brittle stars
Class Echinoidea – sea urchins
Class Holothuroidea – sea cucumbers
Class Crinoidea – sea feathers

12. Class Asteroidea

13. Sea Stars The oral surface of each arm has a single ambulacral groove
Have a large coelom where all the main organs occur

16. Sea Star Feeding
Feed mainly on slow moving, sedentary, or sessile invertebrates
Some species evert the stomach onto prey and digest externally, others swallow whole

17. Pedicellariae
Specialized pinchers found on the aboral surface.

18. Reproduction Sexual Reproduction
Can reproduce asexually by disk division
Sexual Reproduction
Dioecious with sperm or eggs produced in 2 or more gonads in each arm
Larval stage = bipinnaria

19. Regeneration
Many species autotomize, leaving predators with a nutritious souvenir while they escape
Most spp. can regenerate from fragments that include the disk

20. Class Echinoidea Ossicles are joined to form a rigid test
Defining characteristics
Ossicles are joined to form a rigid test
Adults possess a feeding structure called Aristotle’s lantern
Two attributes: mobile spines, and hollow skeleton or test

21. Aristotle’s Lantern

22. They use these spines for protection against predators.
The spines also act like stilts to keep their bodies up off the ground so the tube feet can pull them around!
They eat mostly algae.
They live mostly attached to rocky crevices, which protect them from waves and tide surges.
They have become a popular item to eat and are being harvested in alarming numbers.

23. Sea Urchin Structure

24. Anatomy of a Sea Urchin

25. Pedicellariae
Pedicellariae prevent fouling of test and are used in defense
More complex than sea stars and are located on tall moveable stalks

26. Ingestion and Digestion
Feed on alga material, encrusting bryozoans or scavenge
Food is chopped by 5 sharp pointed teeth
The digestive system is long to deal with vegetable manner
The anus is located aborally

27. Sand Dollars
Irregular: non-spherical variously depressed
Anus is shifted to the oral surface posterior to the mouth creating bilateral symmetry
The star pattern seen on top of the sand dollars is actually caused by special breathing tube feet!
The mouth is found on the under side of the animal.