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Images below courtesy of BIODIDAC

Class ASTEROIDEA: sea stars [fig. 25.5-25.7]

  • central disc merges gradually with arms
  • carnivorous
  • sea star dissection from the University of Minneota

Class OPHIUROIDEA: brittle stars [Fig. 25.8-25.9]

  • central disc sharply set off from arms
  • feed on suspended microorganisms, detritus
  • S. Hottenrott's The Ophiuroidea page has a wealth of information including links to ophiuroids as all-seeing eyes research reporeted in Nature

Class ECHINOIDEA: sand dollars and sea urchins [Fig. 25.10-25.11]

  • compact body, spherical or flattened
  • no arms; spines
  • mainly herbivores
  • Aristotle's lantern
  • pedicelleria.

Class HOLOTHUROIDEA: sea cucumbers [Fig. 25.12-25.13]

  • bilaterally symmetric--slug-like
  • leathery skin
  • suspension or detritus feeders.
  • respiratory trees
  • more information and pictures from the Tree of Life

Class CRINOIDEA: sea lilies [Fig. 25.1, 24.14, 25.15]

  • usually stalkedcup
  • branched arms for filter feeding
  • dorsal mouth
  •  more information and pictures from the Tree of Life


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