1. Seastars, Sandollars, Sea cucumber, Sea urchins
Phylum Echinodermata
Seastars, Sandollars, Sea cucumber, Sea urchins

3. A. General Information
1. Includes sea stars, sea urchins, sand dollars and sea cucumbers
2. strictly marine  over 2,000 species
3. Radial symmetry  good advantage

4. 5. Mostly benthic  live on sea floor
4. Echino is Greek for “spiny” and dermata means skin  “spiny skin”
5. Mostly benthic  live on sea floor
6. Complete digestive system  mouth, intestine, and anus
7. Can regenerate lost body parts
***8. Water vascular system  only animal with water vascular system

5. B. Water Vascular System
1. Used for feeding and locomotion
2. A hydraulic network  uses the power of water to function
3. Found only in echinoderms

6. 4. How it works
a. On dorsal side (top) of echinoderm there is a sieve- like plate
madreporite - the opening to the water vacular system
b. Connected to the madreporite is a short canal stone canal;
helps filter-out debris

7. c. Connected to the stone canal is. a circular canal that runs
c. Connected to the stone canal is a circular canal that runs around the central disc  the ring canal
d. The ring canal is connected to the radial canals run the length of each arm

9. e. Located along the radial. canals. are 1000s of “little
e. Located along the radial canals are 1000s of “little suction cups” called tube feet 
used for locomotion, grasping & feeding
f. Tube feet can extend and contract by a balloon-like structure called an ampulla;

10. Movement of tube feet
11:06
Echinoderms 10

12. h. Each tube foot has its own ampulla
g. ampulla pushes water into tube feet to extend them; “sucks” and hold water to contract them
h. Each tube foot has its own ampulla
i. The water vascualr system allows the echinoderm to be a persistant predator and have excellent adhesive abilities.

13. dorsal view
8. arm
7. Anus
5. madreporite
6. Central disk

14. 1. eyespot
3. tubefeet
4. mouth
2. Ambulacral groove
Ventral view

15. 19. madreporite
22. Radial canal
20. Stone canal
23. Tubefeet
21. Ring canal

19. Water-Vascular System of a Sea Star
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Water-Vascular System of a Sea Star
Fig. 16.4
16-3

20. 10. ring canal
9. Stone canal
13. radial canal
11. Madreporite
14. Ampulla –not extended
17. ampulla; extended

21. C. The 5 Classes of Echinodermata
1. Class Asteroidea
-Includes the seastars (starfish)
-A central disc with five or more arms that radiate in all directions
-Mouth on underside (ventral)
-Anus on dorsal side (top)

23. -At end of each arm are eyespots –
they’re only light sensitive;
-Each underside of arm has ambulacral groove –
a deep groove that runs the length of the arm;
this is where the tubefeet are housed

24. Outer skin has projections all over called spines
also has gills
tiny hairs called cilia
tiny pinchers called pedicellariae –
main function is to keep the top side of the seastar cleaned so gills do not get clogged

25. Pedicellaria
Spine
Pedicellaria
Dermal
branchia
Echinoderms 25

26. Reproduction in seastars – separate sexes;
sperm and eggs are released into water and unite;
“baby” seastars start as a bilateral individual then grows into a radial adult

27. -Sea stars live 3 to 5 yrs.
-Sea stars do have great regenerating powers;
most have to have a portion of central disc to regrow
-Sea stars feed on bivalves (clams, etc…) small crabs, snails & coral

28. -Sea stars use their 1000’s of tubefeet to eat and to move
-Since the tubefeet are part of the “hydraulic” system they have no
problem “prying” open bivalves

29. -The tubefeet wear out the muscle of the bivalve;
opens slightly, the seastar inverts its stomach into the bivalve and eats
-A sea star can take an hour to a week to feed on one bivalve

32. 2. Class Ophuroidea
-Includes brittle stars & basket stars
-Have flattened, round central disc
-Very delicate, found only in well protected waters or areas
-Arms are easily broken off, but have great regenerating powers

35. -Arms are very slender and flexible
-Brittle stars only have 5 arms; basket stars have lots of arms > looks like a tumbleweed
-Arms have sticky secretions to capture prey
-Feed on plankton or dead material
-Lack an anus, waste exits mouth

36. -Tube feet have no suction cups, mostly use flexible arms for
“swimming”
-Feed at night
-Arms capture prey and move food to mouth
-Separate sexes and outside fertilization

37. 3. Class Echinoidea
-Includes sea urchins & sand dollars
****-Lacks arms
-Covered with spines -> “Echinos” means hedgehog
-have anus, mouth, & large stomach

38. -Protected by a structure called a. test – “skeletal structure or
-Protected by a structure called a test – “skeletal structure or shell”
-Mouth consist of five “teeth” that are sharp,
teeth from a structure called Aristotle’s Lantern
-Very few enemies - spines & teeth, which are not easily digested

40. -Separate sexes; eggs of sea urchin is high dollar eating
-Sand dollars protect themselves by burrowing into sand
-Sea urchins attach themselves to rocks, reefs, etc;
they have great suction ability

41. -Both filter in dirt and eat the organic material absorbed by sand or
scrape the ground with teeth; some feed on algae
-Some sea urchins are poisonous

42. 4. Class Holothuroidea
-Includes sea cucumber
-Looks like a cucumber
-Has no spines, instead has “leathery casing” that can extend or contract,
- when contracted, very thick and hard

48. -Have 5 regions - run from mouth to anus forming a “circular casing”
-Have tube feet on 3 regions
-Breathe through respiratory tree
-When unhappy, sea cucumbers ejects inwards
-Can regenerate lost organs

50. -Feeds by “vacuuming” up. sediments and absorbing
-Feeds by “vacuuming” up sediments and absorbing nutrients from the sediments
-Releases waste in long “rolled” links
-When fully extended it can be up to 6 ft. in length, very soft flexible

54. -Good eating –> used in soups, jerky, etc…
-Found in all oceans even Antarctic
-Lives 5-10 yrs.

55. 5. Class Crinoidea
-Includes sea lily & feather stars
-Oldest living echinoderms & most primitive
-Live at depths of 100m or more
-Live on a stalk,
sea lilies are sessile, so have long stalks;
Feather stars are free swimming, and have short stalks

62. -5 or more arms form a “crown” on end of stalk;
arms have more “feathery” attachments (80-200)
-Arms wave through the water to capture prey,
arms bring food to the mouth which faces ***upwards not downward***

65. -Feed on plankton, capture with sticky secretions.
-Bright colors, neat patterns
-Active mostly at night
-Arms roll up when resting
-Regenerating powers-> several weeks to regrow
-Separate sexes->release sperm and egg into water