Echinoderms
Phylum Echinodermata, from the
Greek for spiny skin
Phylum Echinodermata –
spiney-skinned animals
• includes sea stars, brittle stars, sea
urchins, sand dollars, sea cucumbers,
and crinoids
• reverted back to radial symmetry
• tube feet and water vascular system
Echinoderms
Subphylum Asterozoa
• Classes
– Asteroidea (sea star)
– Ophiuroidea (brittle stars)
Subphylum Echinozoa
Classes
– Echinoidea (sea urchin and sand dollar)
– Holothuroidea (sea cucumber)
Subphylum Crinozoa
– Crinoidea (feather stars and sea-lillies)
Characteristics
Adult echinoderms possess
radial symmety
Sea star
Class Asteroidea
Bat star
Brittle star
Class Ophiuroidea
Sea urchin
Class Echinoidea
Purple urchins
Class Echinoidea
Sand-dollar
Sea cucumber
Class Holothuroidea
Feather star Class Crinoidea
Characteristics
• Echinoderms' larvae are ciliated, freeswimming organisms that are
bilaterally symmetrical
Characteristics
• echinoderms do not possess an external skeleton.
• a thin skin covers an endoskeleton made of tiny calcified plates and
spines
• Echinoderms possess a unique water vascular system, a network of
fluid-filled canals that function in gas exchange, feeding, and
secondarily in locomotion
• echinoderms possess a complete digestive tube
• Many echinoderms can regenerate. Some sea stars are capable of
regenerating lost arms. In some cases, lost arms have been
observed to regenerate a second complete sea star.
• the seastar can insert its stomach through the opening of a bivalve
and release gastric juices, digesting the prey alive during feeding
Echinoderm means spiny skin