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 starClass Ophiuroidea

Sea urchinClass Echinoidea

Purple urchins

Sand-dollarClass Echinoidea

Sea cucumberClass Holothuroidea

Feather star Class Crinoidea

Characteristics

• Echinoderms' larvae are ciliated, free-swimming 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