Zoology Chapter 16
Phylum: Echinodermata
Echinos = Spiny
Derma = Skin
Ata= to bear
“bears spiny skin”

Phylum Echinodermata
• 5 Classes
– Class Crinoidea
• Sea lilies
• Feather stars
– Class Asteroidea
• Sea Stars
– Class Ophiuroidea
• Brittle Stars
– Class Echinoidea
• Sea Urchins (venomous)
• Sand Dollars
– Class Holothuroidea
• Sea cucumbers

Characteristics
• Calcareous endoskeleton
– Ossicles- “small bones”
• Adults with pentaradial symmetry (5 points)
– Larvae with bilateral symmetry
• Water-vascular system

Water-vascular system
• Composed of water-filled canals
• Used in
– Attachment
– Feeding
– Locomotion
– Respiration
– Circulation of nutrients and wastes
• Extends to each arm and tube feet
– Tube feet act as suction cups
• Contract & expand

Digestion
• Complete digestive tract
• Eat clams
– Tube feet open shell
– Stomach forced through mouth
– Stomach into opening between clam’s shells
– Digestive enzymes break down tissue
– Sea Star sucks out predigested food
• Eat algae

Nervous System
• Nerve Net
• Nerve Ring
• Radial Nerves
• Eyespots
– Sea stars on each arm

Regeneration & Reproduction
Reproduction
• Mostly dioecious; but no sexes
• Sexual & Asexual
• 2 Gonads are present in each arms
Regeneration
• Broken arms
• New body from broken arm
• Pearl Diver Story
• A form of Asexual Reproduction