kingdom animalia phylum echinodermata

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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 (


  • KINGDOM ANIMALIAPhylum Echinodermata

  • Members of the Phylum EchinodermataDate back 570 million years ago13,000 fossil speciesOnly 7,000 species todayMost are marine and benthic (90%)Range in size (
  • Common Body PlanAdults are pentaradially symmetrical5 sets of body parts around an oral-aboral axis

  • Common Body PlanHowever, larvae are bilaterally symmetricalSettle near adults of their species and attach to substrateMetamorphosis: left side becomes oral surface of the adult and right side becomes aboralLarval mouth/anus disappear, gut migrates to adult position, and new mouth/anus open

  • EndoskeletonUnique system of calcareous plates (ossicles)Reduced in sea cucumbersFused to form a solid test in sea urchins/sand dollars

  • EndoskeletonSkeletal elements bear pincer-like structures called pedicellariaeUse to rid body of debris, defense, grasp objects to hide, or capture/hold prey

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

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

  • Water-vascular systemWater enters bulb, it contracts and water forced into footExtends foot, pressing terminal sucker onto substrateFoot contracts, forcing water back into bulb and raises center of suckerCreates a vacuum seal; only broken when bulb contracts water into foot again

  • ClassificationThere are 6 classes of echinoderms5 classes are described on the following slides

  • Class CrinoideaMost ancient/primitive625 speciesBase of 5 or 10 arms that can branch up to 200 armsSuspension feedersEach arm bears suckerless podia that produce mucus to capture detritus and transport it to mouth

  • Class CrinoideaSessile sea lilyCup-like body attached to stalkAttached to substrateCan bend stalk and flex/extend arms

  • Class CrinoideaFree-moving feather starStalk lost during larval developmentCan crawl/swimJointed appendages (cirri) help it regain balance

  • Class Asteroidea1500 species of sea stars5 or more broad arms surround a central diskCrawl on rocks or live on sea bottomMost are scavengers or predatorsEach arm bears podia with suckersEvert stomach into prey and digest it

  • Class Ophiuroidea2000 species of brittle starsUsually concealed in sand or under objectsSome live in sponges or other colonial organismsOnly 5 arms that are usually highly branched

  • Arms are distinct from central disk Can crawl/clingPredators, scavengers, or suspension feedersFlexible arms bear suckerless podia that secrete mucus to entrap food and transport it to mouth

    Class Ophiuroidea

  • Class Echinoidea1000 species of sea urchins/sand dollarsMovable spines and podia surround body; used for locomotionHerbivorous, detrivorous, suspension feed, a few predators

  • Class EchinoideaUnique feeding apparatus called Aristotles lanternHard plates and muscles just inside mouth Possesses 5 calcareous teethTeeth protract to scrape algae off rocks or tear chunks of kelp

  • Class Holothuroidea1150 species of sea cucumbersMucus-covered oral tentacles trap on plankton or ingest sand organic matterGut modified to produce respiratory trees used for gas exchangeExpel portions of these trees as defense mechanism; regenerate