phylum echinodermata "spiny skin" strangest group in animal kingdom closest invert relation to the...

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  • Phylum Echinodermata"Spiny Skin"Strangest group in animal kingdomClosest invert relationto the ChordatesEndoskeletonjust under skinLack sensory organsNo brainNo clear excretoryor circulatory systems

  • Phylum Echinodermata"Spiny Skin"Possess water vascular systemfor movement and feedingLarval stages are bilaterally symmetricalUndergo metamorphosisto become a radial adultSea stars, brittle stars, sea urchins, basket stars, sea cucumbers, sand dollars

  • Class EchinoideaSea urchinSand dollarClass Asteroideasea starClass Holothuroideasea cucumberClass Ophiuroideabrittle star

  • Body Plan - External Anatomy

  • Body Plan - External AnatomyMadreporite PlateSensory TentaclesSpiny Skin

  • Body Plan - External Anatomy

  • Body Plan - External AnatomyOral ViewDermal SpinesTube FeetPeristomeMouth

  • Internal AnatomyLack many common organ systems

    Nervous SystemDecentralized nervous system with: 1) central ring of ganglia 2) nerve net 3) radial nerves

    Amazing ability to regenerate arms and some organsAutotomy - can intentionally lose an arm to avoid predation

  • Water Vascular SystemUsed for locomotion, feeding, waste removal and respirationSystem composed of canals connecting tube feetWater enters through Madreporite, then passes through stone canal to ring canalHydraulic system allows for powerful but slow movement

  • RespirationClass Holothuroidea - use respiratory tree

    Class Asteroidea - use combination of gills and tube feet

  • Digestive System

    Complete systemFood travels from mouth to cardiac stomach to pyloric stomach, to intestine to anusCan continually digest and ingest food

  • Reproductive SystemSeparate sexes but impossible to tell differenceGonads present in arms

    Life CycleBilateral larva --> Metamorphosis --> Radial Adult