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Echinoderms

Echinoderms. Echinodermata. Domain: Eukarya Kingdom: Animalia Phylum: Echinodermata Class: Asteroidea Class: Ophiuroidea Class: Echinoidea Class: Holothuroidea Class: Crinoidea. Phylum Characteristics. Name means “Spiny Skin”

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Echinoderms

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  1. Echinoderms

  2. Echinodermata • Domain: Eukarya Kingdom: Animalia Phylum: Echinodermata • Class: Asteroidea • Class: Ophiuroidea • Class: Echinoidea • Class: Holothuroidea • Class: Crinoidea

  3. Phylum Characteristics • Name means “Spiny Skin” • Most closely related group to the Chordate organisms (us) • Radially symmetrical – Evolved secondarily – Specifically called Pentaradial symmetry Body parts extend from center along 5 spokes • Body Support Endoskeleton – consists of: • CaCO3 plates called ossicles • Tiny spines or spicules from ossicles may protrude through skin • Cephalization: no distinct head region

  4. Characteristics Body Cavity Characteristics –Coelomate Nervous system – Nerve ring encircling mouth – Radial nerves down each arm – Nerve net spread along exterior surface – Some (Sea Stars) have eye spots at the end of the radial nerves Digestive System – One-way Gut: Mouth, stomach, intestine and Anus opposite mouth Reproductive System • Both Sexes • release eggs and sperm into water • Bilaterally Symmetrical Larvae develop and settle onto sea floor as mini adult

  5. Water vascular system Function: – Network of water-filled canals connected to tube-feet • a major part of the Circulatory and Respiratory Systems Madreporite - Water enters through sieve-like plate on aboral surface – travels through Stone Canal into Ring Canal and down the Radial Canals and into Tube-feet – aid in movement, feeding, respiration, and excretion Ampulla - bulblike sac on upper end of each foot inside body where water is forced into the tube foot.

  6. Example Organisms • Class Asteroidea • - Sea Stars • Class Ophiuroidea -Brittle Stars • Class Echinoidea - SeaUrchins, Sand Dollars • Class Holothuroidea -Sea Cucumbers • Class Crinoidea - • Sea Lillies

  7. Echinodermata Part II Domain: Eukarya Kingdom: Animalia Phylum: Echinodermata Class: Asteroidea Class: Ophiuroidea Class: Echinoidea Class: Holothuroidea Class: Crinoidea

  8. Class Asteroidea – Sea StarsExternal Structure 5 arms typically • Tube feet - 2 rows on underside – Line the ambulacral groove • Oral surface – side where mouth is located • Aboral surface – side opposite mouth • Pedicellariae – tinypincers near spines on aboral surface that keep skin clean of algae and parasites

  9. Mysterious epidemic devastates starfish population off the Pacific Coast https://www.youtube.com/watch?v=2_I_B6U0GtI

  10. Feeding/Digestive System • Tube feet grip prey • Two Stomachs – Cardiac Stomach – can be turned inside out through the mouth through a process called eversion – Pyloric stomach – connectedto digestive glands in each arm – Where absorbtion occurs • Coelomate body cavity – nutrients absorbed into and moved through cavity no specific circulatory system

  11. Reproduction • Separate sexes • External Fertilization – Eggs and sperm shed into water – Larvae – is bilaterally symmetrical • Metamorphosis into pentaradial symmetry for adults • Regeneration – Arms regenerate if a portion of central disc is attached – A slow process

  12. Class Ophiuroidea • Brittle Stars • Thinner arms – Sometimes with distinct spines • Distinct body (central disc) • Do not use tube feet for walking – Tube feet create mucous strand which catch food and move it toward mouth – Will also grab food and bring it to mouth with curled arm

  13. Class Echinoidea • Sea Urchins – Still have 5 regions • Similar to Sea Star folded with arms above aboral surface, then fused together • Spines are all under individual muscle control – often have toxins – Used for protection • Aristotle’s Lantern – Teeth used to feed on algae • Test – name of endoskeleton

  14. Echinoidea cont • Sand Dollars- “flattened urchins” – Suspension feeders – Burrow sideways into sand – Spines used for movement - not tube feet • Test – name of endoskeleton Army of Sea Urchins - Planet Earth - BBC Wildlife https://www.youtube.com/watch?v=D3W4OCnHyCs

  15. Class Holothuroidea – Sea Cucumbers • Mouth at one end • Anus at opposite • Still 5 rows of tube feet –Moved down to one side of organism • No ossicles • Soft body • Madreporite is internal • Some tube feet are tentaclelike for feeding, others moplike for sponging up organic material

  16. https://www.youtube.com/watch?v=vsLBOkYLLeI • Sea Cucumber

  17. Class Crinoidea • Example: Sea Lillies • All are suspension feeders • Use tube feet to secrete mucous which traps food • Food is passed down food groove in center of arms • Evolutionarily oldest • No spines, no madreporite or pedicellariae

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