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Phylum Echinodermata

Phylum Echinodermata. Phylum Echinodermata. Characteristics: Endoskeleton Calcareous (calcium carbonate) Ossicles arise from mesodermal tissue Pentaradial symmetry as adults 5 sections branch off from disk Bilateral symmetry as larvae. Phylum Echinodermata. Characteristics

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Phylum Echinodermata

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  1. Phylum Echinodermata

  2. Phylum Echinodermata Characteristics: • Endoskeleton • Calcareous (calcium carbonate) • Ossicles arise from mesodermal tissue • Pentaradial symmetry as adults • 5 sections branch off from disk • Bilateral symmetry as larvae

  3. Phylum Echinodermata • Characteristics • Water-vascular system • Helps with locomotion, attachment, and feeding • Water-filled canals with extensions called tube feet • Includes a ring canal that surrounds the mouth • Complete digestive tract • Nervous system • Nerve net • Nerve ring • Radial nerves

  4. Phylum Echinodermata • History • Share an ancestor with hemichordates and chordates • Evolved from bilaterally symmetrical ancestors

  5. Phylum Echinodermata • Echinoderm Anatomy • Tube Feet- extensions of the canal system • Inside- bulblike ampulla • Contracts & forces water into the tube from the water-filled canals • The tube feet then extend • Suction cup at the distal end • Used for locomotion and/or feeding

  6. Phylum Echinodermata • Echinoderm Anatomy • Water-Vascular System • Water enters mouth (surrounded by the ring canal) • Ring canal opens to the body through a stone canal (with an opening called a madreporite) • Polian vesicles- sacs connected to the ring canal • Function in fluid storage • Canals branch from the ring canal to transport water to the ampulla (internal portion of the tube feet)

  7. Phylum Echinodermata • Echinoderm Anatomy • Hemal system- strands of tissue that encircle the ring canal • Circulates fluid using cilia • More than likely helps to distribute nutrients (definite function is unknown)

  8. Class Asteroidea • Sea stars • 1,500 species • Live on hard substances, in sand, or in mud • Brightly colored • Red, orange, blue, or gray • 5 arms- radiate from central disk • Pedicellariae • Pincherlike • Clean the body surface of debris • Also function in protection Pedicellariae

  9. Class Asteroidea • Maintenance: • Diet- snails, bivalves, crustaceans, & corals • Stomach- fills most of the coelom in the central disk • 2 regions • Larger, oral stomach (cardiac stomach)- receives ingested food • Smaller, aboral stomach (pyloric stomach)- connects to pyloric cecae (absorb the food)

  10. Class Asteroidea • Maintenance • Feeding • Force bivalves apart with the tube feet Clam vs. Sea Star • The sea star inserts the cardiac stomach into the bivalve shell • Gas exchange • Diffusion across tissue • Nervous system • Nerve ring (encircles the mouth) • Radial nerves extend into the arms (control the tube feet) • Respond to light (photoreceptors in the arms) & chemicals

  11. Class Asteroidea • Reproduction & Regeneration • Can regenerate any part of a broken arm • Must at least have a portion of the central disk remaining • Process takes up to a year to complete • Most species are dioecious • 2 gonads in each arm • Reproduce externally • When one sea star releases gametes, pheromones stimulate other sea stars to release gametes

  12. Class Ophiuroidea • Basket stars, brittle stars, & serpent stars • > 2,000 species • Long arms that give central disk a pentagonal shape • Lack suction disks & ampullas • Move like a snake

  13. Class Echinoidea • Sea urchins, sand dollars, & heart urchins • 1,000 species • Sea urchins- live on hard substrates • Sand dollars & heart urchins- live in the sand or mud • Move using spines & tube feet • Feed on algae, bryozoans, coral polyps, & dead animal remains • Aristotle’s lantern • Chewing apparatus that cuts food into smaller pieces

  14. Class Holothuroidea • Sea cucumbers • 1,500 species • Lack arms- crawl around • Lack spines • Tube feet near the mouth act as tentacles • Covered in mucus to trap food • Produce toxins to discourage predators

  15. Class Crinoidea • Sea lilies & feather stars • 630 species • Sea lilies • Attach permanently to a substrate with a stalk • Crown- unattached end • Feather stars • Swim & crawl • Lack nerve ring

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