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KINGDOM ANIMALIA Phylum Echinodermata

KINGDOM ANIMALIA Phylum Echinodermata. Members of the Phylum Echinodermata. Date back 570 million years ago 13,000 fossil species Only 7,000 species today Most are marine and benthic (90%) Range in size (<1cm to 2 m) 5 Classes. Common Body Plan. Adults are pentaradially symmetrical

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KINGDOM ANIMALIA Phylum Echinodermata

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  1. KINGDOM ANIMALIAPhylum Echinodermata

  2. Members of the Phylum Echinodermata • Date back 570 million years ago • 13,000 fossil species • Only 7,000 species today • Most are marine and benthic (90%) • Range in size (<1cm to 2 m) • 5 Classes

  3. Common Body Plan • Adults are pentaradially symmetrical • 5 sets of body parts around an oral-aboral axis

  4. Common Body Plan • However, larvae are bilaterally symmetrical • Settle near adults of their species and attach to substrate • Metamorphosis: left side becomes oral surface of the adult and right side becomes aboral • Larval mouth/anus disappear, gut migrates to adult position, and new mouth/anus open

  5. Endoskeleton • Unique system of calcareous plates (ossicles) • Reduced in sea cucumbers • Fused to form a solid test in sea urchins/sand dollars

  6. Endoskeleton • Skeletal elements bear pincer-like structures called pedicellariae • Use to rid body of debris, defense, grasp objects to hide, or capture/hold prey

  7. Water-vascular system • Hydraulic system of canals and reservoirs controls the movement of tube feet (podia) • Critical to locomotion, gas exchange, feeding, and sensory reception

  8. Water-vascular system • Water enters sieve plate (madreporite) • Flows from stone canal to radial canals in each arm • Lateral canals perpendicular to the radial canal terminate in muscular bulb (ampulla) connected to a tube foot

  9. Water-vascular system • Water enters bulb, it contracts and water forced into foot • Extends foot, pressing terminal sucker onto substrate • Foot contracts, forcing water back into bulb and raises center of sucker • Creates a vacuum seal; only broken when bulb contracts water into foot again

  10. Classification • There are 6 classes of echinoderms • 5 classes are described on the following slides

  11. Class Crinoidea • Most ancient/primitive • 625 species • Base of 5 or 10 arms that can branch up to 200 arms • Suspension feeders • Each arm bears suckerless podia that produce mucus to capture detritus and transport it to mouth

  12. Class Crinoidea • Sessile sea lily • Cup-like body attached to stalk • Attached to substrate • Can bend stalk and flex/extend arms

  13. Class Crinoidea • Free-moving feather star • Stalk lost during larval development • Can crawl/swim • Jointed appendages (cirri) help it regain balance

  14. Class Asteroidea • 1500 species of sea stars • 5 or more broad arms surround a central disk • Crawl on rocks or live on sea bottom • Most are scavengers or predators • Each arm bears podia with suckers • Evert stomach into prey and digest it

  15. Class Ophiuroidea • 2000 species of brittle stars • Usually concealed in sand or under objects • Some live in sponges or other colonial organisms • Only 5 arms that are usually highly branched

  16. Class Ophiuroidea • Arms are distinct from central disk • Can crawl/cling • Predators, scavengers, or suspension feeders • Flexible arms bear suckerless podia that secrete mucus to entrap food and transport it to mouth

  17. Class Echinoidea • 1000 species of sea urchins/sand dollars • Movable spines and podia surround body; used for locomotion • Herbivorous, detrivorous, suspension feed, a few predators

  18. Class Echinoidea • Unique feeding apparatus called Aristotle’s lantern • Hard plates and muscles just inside mouth • Possesses 5 calcareous teeth • Teeth protract to scrape algae off rocks or tear chunks of kelp

  19. Class Holothuroidea • 1150 species of sea cucumbers • Mucus-covered oral tentacles trap on plankton or ingest sand organic matter • Gut modified to produce respiratory trees used for gas exchange • Expel portions of these trees as defense mechanism; regenerate

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