Echinodermata

• Phylum Echinodermata


  Exclusively marine
• Echinodermata


  • Deuterostomes
  • Endoskeleton with epidermis covering
  • Composed of calcium carbonate ossicles
  • May be tightly or loosely joined
  • All members have mutable collagenous tissue
• Types of skeletons observed in animals

  • Endoskeleton
  • Exoskeleton
  • Hydrostatic skeleton
• Echinodermata symmetry


  • Pentaradial as adult
  • Bilateral as larva
• Types of symmetry observed in animals

  • Radial
  • Bilateral
  • Asymmetrical
• All Echinodermata systems are organized with branches radiating from the center
• Echinodermata have a nerve ring with branches as their nervous system
• Echinodermata water-vascular system


  1. Water enters through madreporite

  2. Flows through stone canal to ring canal

  3. Radial canal extends from ring canal into each body branch

  4. Tube feet used for locomotion, feeding, gas exchange
• Echinodermata feeding


  • Mouth on ventral surface
  • Stomach
  • Digestive glands
• Echinodermata regeneration


  • Many able to regenerate lost parts
  • Some can reproduce asexually by splitting
• Echinodermata reproduction


  • Most is sexual
  • Dioecious
  • Gametes released into water
  • Free-swimming larvae
  • Each class has a characteristic type of larva
• Extant classes of Echinodermata

  • Asteroidea (sea stars and sea daisies)
  • Echinoidea (sea urchins and sand dollars)
  • Ophiuroidea (brittle stars)
  • Crinoidea (sea lilies and feather stars)
  • Holothuroidea (sea cucumbers)
• Asteroidea


  • Important predators in many marine systems
  • Abundant in intertidal zones and at great depths
  • Pigmented epidermis
  • Most have 5 arms, some have multiples of 5
• Echinoidea


  • Lack arms
  • Double rows of tube feet
  • Protective moveable spines
  • Calcareous plates
  • Urchin feeding apparatus (Aristotle's lantern)
  • Scraping algae
• Ophiuroidea


  • Largest class
  • Arms are equal diameter their entire length
  • Arms are easily autotomized (spontaneous casting off of a limb or body part)
• Crinoidea

  • arms covered in tube feet
  • filter feeders
  • arms attached to stem