2. GENERAL CHARACTERISTICS
Ex: sea stars, brittle stars, sand dollars, sea urchins, & sea cucumbers
All marine
“Spiny-Skinned Animals”
Radial Symmetry as adults – 5 parts
Regenerate = Autotomy

3. GENERAL MORPHOLOGY
A. INTERNAL SKELETON of Calcareous ossicles (plates)
Variations :
Brittle / Sea Stars – many small plates that move with one another

4. Sea Urchin & Sand Dollar – skeleton plates fused into
Sea Urchin & Sand Dollar – skeleton plates fused into shell called “test”

5. Sea Cucumber – degenerated & buried in leathery body

6. B. Water Vascular System
Used in locomotion, food capture, & respiration
Network of canals – run throughout body ending w/tube feet
Varying internal water pressure can extend or contract tube feet
Tube feet end in small suction cups

7. C.
Mouth on oral surface (bottom / ventral)
Anus on aboral surface (top / dorsal)

8. SEA STARS
5 Arms / Rays 4 – 10”
Prey on bivalves (clams, mussels) & coral
Many eat w/stomach outside body; pop stomach out mouth

9. Have pedicellariae or tiny, forceps-like structures on aboral surf
Have pedicellariae or tiny, forceps-like structures on aboral surf. to pick up & remove dirt

10. Other Body Systems No circulatory, excretory, or respiratory systems
No head or brain
Eyespots on the tips of each arm detect light

11. Reproduction Separate sexes External fertilization
Females produce 200,000,000 eggs / season; meroplankton

12. BRITTLE STARS Most mobile; fast Snake-like movement
Disc .4 – 1.2 “; arms 2 – 2.4 “
Scavengers
In largest class (with basket stars)
Arms break off readily

13. SEA CUCUMBERS Lack arms & visible spines; elongated
Flexible, leathery body
Burrowers

14. 5 rows of tube feet run length of body
10-30 modified tube feet form tentacles around mouth
Tentacles have sticky ends to trap plankton; or eat detritus
Breathes through anus

15. Sea lilies & feather stars
Filter Feeders
Can detach & move around

16. Sea Urchins Spines for protection, moving, trapping food Shell = test
Divided into 10 sections
5 Ambulacral w/tube feet
5 Interambulacral without
Covered w/muscle & skin to help mobility

17. Sand Dollars Flattened version of urchin Live in sand along coastlines
Food falls between dense spines & carried to mouth by cilia & tube feet
        
Tiny, moveable spines for burrowing
Aristotle’s Lantern

18. Sea Biscuits Not as flat as dollars
Live in sand along coastlines; burrow
Tube feet for respiration
Pedicellarea
Eat detritus in sand   
Short dense spines for movement cover test