1. Phylum Echinodermata

2. Phylum Echinodermata Characteristics: Endoskeleton
Calcareous (calcium carbonate)
Ossicles arise from mesodermal tissue
Pentaradial symmetry as adults
5 sections branch off from disk
Bilateral symmetry as larvae

3. Phylum Echinodermata Characteristics Water-vascular system
Helps with locomotion, attachment, and feeding
Water-filled canals with extensions called tube feet
Includes a ring canal that surrounds the mouth
Complete digestive tract
Nervous system
Nerve net
Nerve ring
Radial nerves

4. Phylum Echinodermata History
Share an ancestor with hemichordates and chordates
Evolved from bilaterally symmetrical ancestors

5. Phylum Echinodermata Echinoderm Anatomy
Tube Feet- extensions of the canal system
Inside- bulblike ampulla
Contracts & forces water into the tube from the water-filled canals
The tube feet then extend
Suction cup at the distal end
Used for locomotion and/or feeding

6. Phylum Echinodermata Echinoderm Anatomy Water-Vascular System
Water enters mouth (surrounded by the ring canal)
Ring canal opens to the body through a stone canal (with an opening called a madreporite)
Polian vesicles- sacs connected to the ring canal
Function in fluid storage
Canals branch from the ring canal to transport water to the ampulla (internal portion of the tube feet)

7. Phylum Echinodermata Echinoderm Anatomy
Hemal system- strands of tissue that encircle the ring canal
Circulates fluid using cilia
More than likely helps to distribute nutrients (definite function is unknown)

8. Class Asteroidea Sea stars 1,500 species
Live on hard substances, in sand, or in mud
Brightly colored
Red, orange, blue, or gray
5 arms- radiate from central disk
Pedicellariae
Pincherlike
Clean the body surface of debris
Also function in protection
Pedicellariae

9. Class Asteroidea Maintenance:
Diet- snails, bivalves, crustaceans, & corals
Stomach- fills most of the coelom in the central disk
2 regions
Larger, oral stomach (cardiac stomach)- receives ingested food
Smaller, aboral stomach (pyloric stomach)- connects to pyloric cecae (absorb the food)

10. Class Asteroidea Maintenance Feeding Gas exchange Nervous system
Force bivalves apart with the tube feet
Clam vs. Sea Star
The sea star inserts the cardiac stomach into the bivalve shell
Gas exchange
Diffusion across tissue
Nervous system
Nerve ring (encircles the mouth)
Radial nerves extend into the arms (control the tube feet)
Respond to light (photoreceptors in the arms) & chemicals

11. Class Asteroidea Reproduction & Regeneration
Can regenerate any part of a broken arm
Must at least have a portion of the central disk remaining
Process takes up to a year to complete
Most species are dioecious
2 gonads in each arm
Reproduce externally
When one sea star releases gametes, pheromones stimulate other sea stars to release gametes

12. Class Ophiuroidea Basket stars, brittle stars, & serpent stars
> 2,000 species
Long arms that give central disk a pentagonal shape
Lack suction disks & ampullas
Move like a snake

13. Class Echinoidea Sea urchins, sand dollars, & heart urchins
1,000 species
Sea urchins- live on hard substrates
Sand dollars & heart urchins- live in the sand or mud
Move using spines & tube feet
Feed on algae, bryozoans, coral polyps, & dead animal remains
Aristotle’s lantern
Chewing apparatus that cuts food into smaller pieces

14. Class Holothuroidea Sea cucumbers 1,500 species
Lack arms- crawl around
Lack spines
Tube feet near the mouth act as tentacles
Covered in mucus to trap food
Produce toxins to discourage predators

15. Class Crinoidea Sea lilies & feather stars 630 species Sea lilies
Attach permanently to a substrate with a stalk
Crown- unattached end
Feather stars
Swim & crawl
Lack nerve ring