Phylum Echinodermata
crinoids, brittle stars, sea stars, sea
urchins, and sea cucumbers
Critical Thinking
All echinoderms require oxygen for respiration but
they lack a respiratory system.
As you learn about these interesting animals, figure
out how they get the oxygen required for cellular
respiration to occur.
How is that linked to photosynthesis?
Basic Characteristics
• Symmetry
▫ All echinoderms have Radial
Symmetry
 BUT… they develop from bilateral
larvae
• More closely related to Chordates
than other Invertebrates
▫ Develop as deuterostomes rather
than protostomes
Basic Characteristics Cont’d
• Endoskeleton
▫ Ossicles of calcium carbonate attached to spines or
spicules
 Enchinoderm = “spiny skin”
• Water Vascular System
▫ Water filled canals inside body
• Tube Feet
▫ Small extensions of the water vascular system
▫ Aid in – feeding, movement, respiration, excretion
Classification
7,000 species of echinoderms in 6
classes
Class Crinoidea
Sea Lily
• Examples = crinoids
▫ Sea lilies, and feather stars
• Minimal movement
▫ Some are sessile as adults = sea
lilies
• Tube feet serve as a respiratory
surface
Feather Star – Click Picture
to See Video
Class Ophiuroidea
Basket Star
• Name means “snake like”
• Examples = basket stars and
brittle stars
• Largest Class
▫ Characterized by long narrow
arms which allow quick
movement
Brittle Star
Class Echinoidea
• Name means “spinelike”
• Example = Sea Urchins and
Sand Dollars
• Rigid exoskelton called a test
▫ Encloses the internal organs
▫ Sea Urchin Eating
Click on the picture to view
Sand Dollar Movement
Class Holothuroidia
• Name Means “water polyp”
▫ When their tentacles are extended
they resemble the polyp form of
some cnidarians
• Examples = Sea Cucumbers
• Live on the sea bottom
▫ Crawl and burrow into soft
sediment
• Eats by cleaning food off tentacles
Class Asteroidia
• Name Means “starlike”
• Tube Feet are used in:
▫ Movement
▫ Capturing Prey
▫ Gas Exchange
• Have TWO stomachs – Cardiac and
Pyloric
▫ Digestion occurs in this order:
 Cardiac Stomach – Pyloric
Stomach – Digestive Glands
• Remarkable Regeneration