1. “Spine skin” Marine (or estuarine) Water vascular system
Phylum Echinodermata
“Spine skin”
Marine (or estuarine)
Water vascular system
Pentaradial symmetry

2. Classes: Crinoidea, Stelleroidea, Echinoidea, Holothuroidea
Echinodermata
6500 species living
13,000 from fossils
Classes: Crinoidea, Stelleroidea, Echinoidea, Holothuroidea

3. Water vascular system
Fluid-filled canals that lead to tube feet
Sea star: madreporite, stone canal, ring canal, radial canal, ampulla, tube feet

4. Water vascular system
Tiedemann’s body:
Contains phagocytes; remove foreign matter such as bacteria from incoming seawater

5. Ambulacral ossicles support ampullae and tube feet
Water vascular system
Ambulacral ossicles support ampullae and tube feet
Contraction of ampulla moves fluid to tube feet
Muscles in tube feet for retracting

6. Water vascular system
Cilia on inner surface of tube feet circulate water
Gas exchange
Fluid similar to seawater; contains coelomocytes, proteins, K ions

7. Feather stars and sea lilies Oldest of living echinoderms
Class Crinoidea
Lily-like
Feather stars and sea lilies
Oldest of living echinoderms

8. Feeding, repro structures at top of stalk
Class Crinoidea
Feeding, repro structures at top of stalk
Complete digestive system in calyx: mouth – intestine, anus

9. Arms have ambulacral groove with mucus-secreting glands adjacent.
Class Crinoidea
Arms have ambulacral groove with mucus-secreting glands adjacent.
Food particles stick in mucus, flicked to the ambulacral groove, then mouth

10. Brittle stars, sea stars
Class Stelleroidea
Armed echinoderms
Brittle stars, sea stars

11. Brittle stars and basket stars
~ 2100 described
Joints allow flexibility
Tube feet present
Sensitive to light – oral surface

12. Brittle stars and basket stars
Tube feet through small holes
Digestive system mostly in disc – no anus
Bursal slits for water exchange

13. Brittle stars and basket stars
Deposit feeders, suspension feeders, carnivores, scavengers
Many are nocturnal
Many live in associations

14. Arms not as distinct from disc as in brittle stars
Sea stars
~ 1600 species
Arms not as distinct from disc as in brittle stars
Move slowly with tube feet
Tube feet move individually

15. Figure 20_06

16. Digestion: lower cardiac stomach digests food
Sea stars
Digestion: lower cardiac stomach digests food
Upper pyloric stomach for secreting enzymes and absorption

17. Pedicellariae: stalked or sessile

18. Class Echinoidea: spine-like
Sea urchins, sand dollars
< 1000 species

19. Class Echinoidea: spine-like
Ossicles form test
Complex system of ossicles and muscles for grazing = Aristotle’s lantern

20. Spines attach to skeleton – ball and socket joint
Toxins
Ossicles flat and joined = inflexible

21. Class Echinoidea: spine-like
Tube feet in 5 double rows of plate
Pedicellariae – globular forms have toxin

22. Feeding and digestion:
Aristotle’s lantern
Teeth protruded to scrape algae or consume food
Species w/o lantern usually detritivores

23. Mouth – esophagus – intestine – anus
WVS

24. Class Holothuroidea: sea cucumbers
~ 1200 species

25. Ossicles microscopic
Multiple shapes

26. Tube feet modified into tentacles around mouth
Mostly deposit-feeders, few filter-feeders

27. Digestion system: elongated
Mouth – esophagus – stomach – intestine – cloaca – anus
WVS – madreporite in coelomic cavity = no outside connection

28. Respiratory tree: connects to cloaca – water supply
Expulsion of internal organs

29. Echinoderm repro + development:
Some are asexual
Most are dioecious
Multiple gonads, gametes into seawater = external fert

30. Distinctive ciliated larval form in each class
Free-swimming, planktonic
Metamorphosis into adult

31. Echinoderm NS
No brain
3 nerve networks
Ectoneural = ring around esophagus: receives sensory input