Phylum: Echinodermata

Echinos = SpinyDerma = SkinAta= to bear

“bears spiny skin”

Zoology Chapter 16

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 armsRegeneration • Broken arms• New body from broken arm• Pearl Diver Story• A form of Asexual Reproduction