Phylum Echinodermata Spiny Skin. Advanced?  Skeleton is internal test comprised of individuals plates of porous high-Mg calcite.  Bilaterally symmetrical

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  • Phylum EchinodermataSpiny Skin

  • Advanced?Skeleton is internal test comprised of individuals plates of porous high-Mg calcite. Bilaterally symmetrical larvaeAdult typically has pentaradial symmetryWater vascular system instead of musclesHighly regenerative can eviscerateSeparate sexes: External fertilization

  • Yet simple!Light sensitive eyes at the end of each ray no vision, no brain , no headReduced internal organs no respiratory circulatory, excretory, nervous systemAdults have pentamerous radial symmetryRespiration is by diffusion through skin.

  • Starfish are scavengers and eat a variety of organisms. They can open a clam shell a few centimeters wide. Then by inverting its stomach into the shell, the clam is digested and absorbed.

  • Missing parts from injury or evisceration are quickly replaced. Any portion of the central disk will regenerate a new starfish.

  • The ClassesCrinoideaOphiureideaHolothuroideaAsteroideaEchinoidea

  • Crinoidea ( Feather Stars, Sea lillies)Upside down brittle starMay have a stalkCirri used like a holdfastCatches food with tube feetAncient

  • Ophiurroidea (brittle star)Arms distinctly set off from central diskTube feet with no suckers. Moves by lashing armsClosed ambulacral groove, no gut branches in arms.

  • Holothurudoidea (Sea Cucumber)Soft, cucumber shaped bodySuckered tube feet in 5 longitudinal rowsTentacles around mouth (modified tube feet)Suspension, detritus or deposit feeders

  • Sea Cucumber Anatomy

  • Asteroidea (Sea Stars)Star shaped bodyTube feet with suckersOpen ambulacral groovesMost have pedicellariaeThought to be used in defenseMostly predatorsFeed by everting portion of stomach

  • Sea Star Basic Anatomy

  • Feeding

  • Echinoidea (Urchins and Sand Dollars)Skeleton = test CaCO3 ossicles are fusedTube feet with suckersMoveable spines and pedicellariaeFeed on algae, encrusting animalsMouth is referred to as Aristotles lantern

  • Sea Urchin

  • EcologyExclusively marine: Echinoderms lack osmoregulatory mechanisms that might allow them to live in brackish or fresh water Urchins may control algae growth on reefsSea Stars are important inter-tidal predatorsMake up an estimated 90% of deep sea biomassMay regulate growth of sessile organisms