Phylum Echinodermata

Who is in phylum Echinodermata?

Sea stars

Brittlestar

Sea urchin

Sand Dollar

Sea cucumbers

Sea Biscuit

Crinoids

General Characteristics

• Translation: Spiny - Skin

(echino = spiny; derm = skin)

• Main features
• Spiny skin
• Penta-radial symmetry - radial symmetry based on 5 parts
• Endoskeleton - internal skeleton
• Water vascular system - controls internal water pressure for movement (tube feet)

Water Vascular System

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General Characteristics cont.

• All marine
• Benthic
• Regenerative abilities

Class Crinoidea

Feather stars and sea lilies

• Appear plant-like
• Long feather like arms
• Short hook-like legs (cirri) - used for anchorage and hunting

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Class Asteroidea

Sea stars

• Tube feet
• Arms carry equal portion of animal’s system and organs
• Invert stomach to feed, dissolving prey alive
• Regenerative abilities
• Regenerate lost limb
• Some can grow new animals when cut in pieces

Sea stars

Crown of thorns sea star

• Caused extreme destruction on Australia's Great Barrier reef
• Consume coral
• Indo-Pacific Distribution
• 14-21 arms

Class Ophiuroidea

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Brittle Stars

• Longer and thinner legs than sea stars
• Found in deep and shallow water
• Some are bioluminescent

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Class Echinoidea

Sand Dollars (A), Sea Urchins (B), and Sea Biscuits (C)

• 5 section body, but no arms
• Disk shaped body
• Tube feet

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C

B

A

Sea Urchins

• Graze on algae
• Spines
• Some species have toxins in spines for self defense
• Help with locomotion
• Extension of skeleton
• Only edible echinoderm (Uni = gonads)

Class Holothuroidea

Sea Cucumbers

• Pull sand and organic matter through mouth to feed
• Defense
• Tough skin
• Evisceration - expel internal organs (takes 2-4 weeks to regenerate organs)