1. Echinoderms
Section 38.1

2. Echinoderms
Examples: sea stars, sand dollars, sea urchins, & sea cucumbers
Marine environments
Brilliantly colored
Radial symmetry

3. 4 Unique Characteristics:
Ossicles: calcium carbonate plates that make up exoskeleton
Water-vascular system: network of water-filled canals inside body

4. 3. Tube feet: small, movable extension of w-v system which aid in movement, feeding, respiration, & excretion
4. Pentaradial symmetry: body parts extend from center along 5 spokes

5. Classification
6 classes of echinoderms (only 5 discussed in textbook):
Class Crinoidea
Class Ophiuroidea
Class Echinoidea
Class Holothuroidea
Class Asteroidea

6. Class Crinoidea Examples: sea lilies, feather stars
Crinoid means “lily-like”
5 main arms that branch to form up to 200 more arms
Filter feeders
Mouth faces up

7. Class Ophiuroidea
Largest class with examples such as basket stars & brittle stars
Ophiuroidea means “snake-tail”
Live on bottom of ocean
Regeneration of broken arms
Long, narrow arms allow for quick movement

8. Class Echinoidea Examples: sea urchins & sand dollars
Echinoidea means “spinelike”
Test: compact, rigid endoskeleton that surrounds internal organs
Spines can have barbs or venom

9. Class Holothuroidea Example: sea cucumber
Holothuroidea means “water polyp”
Armless
Ossicles are not connected thus soft bodies
Tentacles around mouth to capture prey

10. Class Asteroidea Example: sea star (starfish)
Asteroidea means “starlike”
Variety of sizes, shapes, and colors
Compete with humans for oysters, clams, etc

11. Sea Stars
Section 38.1 continued

12. External Structure Several arms extending from central region
Two rows of tube feet on underneath side of each arm
Oral surface: side where mouth is located
Starfish = underside
Aboral surface: side opposite of mouth

13. Rough texture due to short spines
Pedicellariae: tiny pinchers surrounding of each spine that keep body free of foreign objects

14. Water-Vascular System
Network of water-filled canals that are connected to the tube feet
Water movement:
Madreporite (sievelike plate on aboral surface)  stone canal  ring canal (encircles mouth)  radial canal (extends to each arm)  tube feet
Ampulla: bulblike sac at end of tube feet that allows for movement and suction

15. Feeding & Digestion Prey: mollusks, worms, clams
Cardiac stomach: can be turned inside out through mouth during feeding
Digestive pathway:
Mouth  cardiac stomach  pyloric stomach  digestive glands in each arm  anus

16. Other Body Structures
No circulatory, excretory, or respiratory systems!
Skin gills: thin walls of tube feet that allow gas exchange
Nervous system = nerve ring (around mouth), radial nerves (length of each arm), eyespots (end of each arm), tentacles

17. Reproduction & Development
Separate sexes – each arm has sex organs
External fertilization
After 2 months of swimming they settle to bottom of ocean and metamorphous into adult
Regeneration (asexual)
As long as part of the central region stays in tact