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Echinoderms

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  1. Echinoderms Chapter 16

  2. Echinoderms • Phylum Echinodermata • 400-million years old • 12-18 classes have gone extinct • Sea stars, sea urchins, sand dollars, and sea cucumbers

  3. Echinoderms • Characteristics • 7,000 species • All are marine • Most are pentaradial, but some have reverted back to bilateral symmetry

  4. Echinoderms • Calcareous endoskeleton • Series of ossicles or calcium carbonate plates • May be the reason for pentaradial symmetry

  5. Echinoderms • Water-vascular system • A series of water-filled canals • Tube feet - extension of the water vascular system • Usually has a suction cup at the end

  6. Echinoderms • Ring canal • Five branches come from this canal • Opening is called the madreporite • Brings water in or out for water loss or to equalize pressure • Tiedeman bodies and Pollian vessicles

  7. Echinoderms • Tube Feet • Extension of the canal system • Suction cup externally • Ampulla • Is a pump like structure that forces water into the tube feet

  8. Echinoderms • Complete digestive tract • Complete nervous system • Contains nerve net, nerve ring, and radial nerves

  9. Echinoderms • Hemal system • Strands of tissue that encircle the echinoderm • These strands use cilia to circulate fluid

  10. Echinoderms • Class Asteroidea • 1,500 species • Sea stars or starfish • Eat snails, bivalves, crustaceans, polychaetes, corals, and others.

  11. Echinoderms • Many sea stars digest their prey whole • Some pry open bivalves • Once the bivalve is open 0.1 mm digestion begins • Pyloric ceca

  12. Echinoderms • Regeneration • Can regenerate any part of a broken arm • Some can regenerate an entire sea star • Dioecious • External fertilization • Embryos are planktonic • Goes through two larval stages before metamorphosis

  13. Echinoderms • Class Concentricycloidea • Sea daisies • Highly modified member of Astroidea • Lack arms • < 1 cm in diameter • Lack internal digestion

  14. Echinoderms • Class Ophiuroidea • Brittle and basket stars • > 2,000 species • Tube feet do not contain suction disks • Madreporite is located on the mouth

  15. Echinoderms • Water-vascular system is not used for locomotion • Very flexible compared to starfish • Snake-like arms are used to wrap around objects

  16. Echinoderms • Predators and scavengers • No intestine, short digestive tract • Bursae release nitrogenous waste through the tube feet • Autotomy - used for defense arms fall off • Dioecious

  17. Why do starfish get up in the middle of the night?

  18. Because they have to twinkle!

  19. Echinoderms • Class Echinoidea • Sea urchins, sand dollars, and heart urchins • 1,000 species • All marine environments

  20. Echinoderms • Sea Urchins • Sea urchins live in crevices • Rounded in shape • Skeleton is called a test • Ten sets of plates • Pedicellariae – contains two to three jaws • Some contain venom which can also be injected into the predator

  21. Echinoderms • Types of Pedicellariae • Forceps type (A), Scissors type (B, C), Tridactyl (B, D), Globiferous (E)

  22. Echinoderms • Oral end faces toward the surface • Eat algae, bryozoans, coral polyps, and dead animals • Aristotle’s Lantern is used for chewing

  23. Echinoderms • Sand dollars • Burrow under the sand • Dioecious • External fertilization • Larvae live in plankton

  24. Echinoderms • Echinoderm larvae • Asteroids (A, B), Ophiuroids (C), Echinoids (D), Holothuroids (E), Crinoids (F)

  25. What fish is asked to sign autographs?

  26. A starfish.

  27. Echinoderms • Class Holothuroidea • 1,500 species • Sea cucumbers • All depths and all oceans

  28. Echinoderms • No arms • Elongated body • Tube feet or tentacles surround the mouth • Arrangement of 10-30 tube feet • Range in size from 10-30 cm

  29. Echinoderms • Thick body wall with no spines • Move by worm-like crawling, some swim • Respiratory trees circulate water and nitrogenous waste • Madreporite is internal

  30. Echinoderms • Many defense mechanisms • Body wall toxins • Everting tubules of respiratory tree (Cuverian tubules) • Evisceration • Dioecious • External Fertilization • Planktonic larvae

  31. Echinoderms • Class Crinoidea • Sea lilies and feather stars • 630 species • Most ancient of echinoderms

  32. Echinoderms • Sea lilies attach permanently to the substrate • Attached segment bears projections called cirri • Unattached end is called the crown • Feather stars swim and crawl

  33. Echinoderms • Suspension feeders • Lack nerve ring • Most are dioecious, but some are monoecious • Protandry • Regeneration can occur