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Phylum Echinodermata (Body Structure (Chordate-like characteristics…
Phylum Echinodermata
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Taxonomic Division
Class Crinoidea
Cup- shaped body with pinnate (feather-like), long, hollow ambulacra (multiples of 5) for filter feeding; oral surface bears both mouth and anus and faces up; all organs within cup-shaped body (calyx); tube feet lack suckers; madreporite absent; doliolaria larva
Class Asteroidea
Thick ambulacra project from a central disk; ambulacra not distinct from the central disk; organs extend into the ambulacra; tube feet usually have suckers and are located within open ambulacral grooves; bipinnaria and brachiolaria larvae; anus and madreporite on aboral suface; dermal branchiae as accessory respiratory structures
Class Ophiuroidea
Slender ambulacra project from the central disk; ambulacra are distnct from the central disk and all organs are contained within the central disk; ambulacral grooves covered by vertebra-like ossicles; ophiopluteus and vitellaria larvae; madreporite on oral surface; anus absent, bursae as accessory structures
Class Echinoidea
Hemispherical or flattened echinoderms with the body enclosed by a continuous test covered with epidermis; may have movable long or short spines; closed ambulacral groves; usually with a chewing apparatus (Aristotle's Lantern); echinopluteus larvae; anus and madreporite on aboral surface; peristomial gills as accessory respiratory structures
Class Holothuroidea
Cylindrical body elongated in the oral/aboral axis; exhibit tertiary bilateral symmetry; arms are absent and tube feet at anterior end are modified into tentacles; endoskeleton composed of microscopic, separate ossicles embedded in a thick, muscular, leathery body wall; no spines; auricula and doliolaria larvae; internal madreporite, anus at aboral end; respiratory tree as accessory respiratory structure
Body System
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Nervous system --- radial nervous system
-- circumoral and circumanal nerve rings with radial nerves
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