Phylum Echinodermata

• Deuterostomia– Anus forms from or near

blastopore– Mouth forms secondarily

Protostomes vs Deuterostomes

Plutei

Echinoderm Development

• Metamorphosis of bilaterally symmetric larvae to pentaradial adults

Deuterostome Phylogeny

Echinoderm Phylogeny

Echinoderm Symmetry• Primary bilateral symmetry

– Larval forms– Some adult forms

• Secondary pentaradial symmetry– 5 radial divisions of major

organ systems

Phylum Echinodermata

• Spiny skin• Endoskeleton

– Dermal ossicles– CaCO3, Ca2(PO3)2

Pedicellaria

Phylum Echinodermata

• Water vascular system

Water Vascular System & Tube Feet

Tube Feet

Hemal Canals

Class Asteroidea

• Central body disc• Most frequently 5 arms• Regeneration

Starfish & Sea Stars

Asteroidea Anatomy

Asteroidea Anatomy

Regenerating Arms

Commensals of Echinoderms

Class Ophiuroidea

Brittle StarsSea baskets

Reduced central discReduced tube feet

Class OphiuroideaSea baskets

Basket stars

Ophiuroidea Anatomy

Ophiuroidea Anatomy

Class Echinoidea

Sand dollars

Sea urchins

Sea biscuits

Echinoid Anatomy

Echinoid Mouth – Aristotle’s Lantern

Class HolothuroideaSea Cucumbers

Holothuroidea Anatomy

Holothuroidea Defense Reaction

• Eversion of the respiratory tree and lower intestine

• Some species produce toxins

Class Crinoidea

Feather StarsSea Lillies

Sessile Crinoids

Swimming Crinoid

Crinoid Anatomy