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Phylum Echinodermata By: Kane Richardson Basics About Echinoderms • Echinoderm means “spiny skin”. • Approximately 7,000 living species. • Mainly a marine group echinoderms are found in all the oceans. • Most radially symmetric animals are sessile, however, echinoderms are able to move. 5 Classes of Echinoderms • Class Asteroidea- Sea Stars • Class Ophiuroidea- Brittle Stars • Class Echinoidea- Sea Urchins • Class Holothuroidea- Sea Cucumbers • Class Crinoidea- Sea Lilies Class Asteroidea • Mainly a marine group, found in all oceans. • Can range from less than 2 cm to over 1 m. • Majority have 5 arms, but some can have up to • • • • 40. Can regenerate arms. Some can reproduce asexually. Mainly have separate sexes, but some are hermaphroditic. Mainly scavengers and carnivours. Class Ophiuroidea • Are carnivores, filter feeders, and scavengers. • Gas exchange and excretion occur through cilia-lined sacs called bursae. • 2,000 identified species. • Usually have separate sexes. Class Echinoidea • Approximately 900 species. • Worldwide in marine habitats. • Commonly grouped as regular or irregular, with the • • • • greatest differences pertaining to the oral structure, shape of the organism, and the location of the anus. Regular are the sea urchins. Irregular are the sand dollars. Have an internal skeleton. Spines and tube feet surrounding the peristome function in locomotion, burrowing, and food-gathering. Have separate sexes. Class Holothuroidea • • • • • • • • • About 1,100 described extant species. Found in oceans all over world. First fossil record 500 million years ago. Most are black, brown, or olive green. Ranging from 3 cm to 1 m long. Five rows of tube feet running from the mouth to the anus along the cylindrical body. 10 to 30 branching tentacles surrounding mouth. Most species live from five to ten years. Trap particles and plankton on mucus-covered tentacles. Class Crinoidea • Around 600 species. • Two body regions, the calyx and the rays. • Filter feeders. • Rays are most important for locomotion. • Approximately 5,000 species of fossil crinoids are known.