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Phylum Echinodermata

Phylum Echinodermata. Diversity. Over 7,000 species worldwide Live in aquatic, marine environments Name “ Echinodermata ” comes from their external spines Notable characteristics: 1) Spiny endoskeleton of plates 2) Water-vascular system 3) Special outer layer ( pedicellariae )

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Phylum Echinodermata

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  1. Phylum Echinodermata

  2. Diversity • Over 7,000 species worldwide • Live in aquatic, marine environments • Name “Echinodermata” comes from their external spines • Notable characteristics: • 1) Spiny endoskeleton of plates • 2) Water-vascular system • 3) Special outer layer (pedicellariae) • 4) Respiratory system: dermal branchiae • 5) Radial symmetry (in adults) • 6) VERY bizarre and unique animals

  3. Diversity • Examples include: • starfish/sea star, brittle star, sea cucumber, sea lilies, sea daisies, sea urchins • Fill a wide range of ecological roles and have enormous variation • Food, bioindicators, decoration, etc • Called Echinoderms • Echinoderm means “prickly skin”

  4. Characteristics of EchinodermsBody type and Symmetry • Body is unsegmented • Radial symmetry • Arranged around a central point • Pentaradial - Most have five parts (called ambulacra) that radiate outward • Adult form radial/larva bilateral • Body shape • Round, cylindrical or star-shaped • Body contains spines • Can be external or internal

  5. Characteristics of EchinodermsExternal Features • Endoskeleton • Made of calcium (dermal calcareous ossicles) • First endoskeleton we’ve seen (besides one exception in Mollusks)

  6. Pedicellariae which keep debris off body, protect animal and food capture

  7. Characteristics of EchinodermsReproduction • Asexually (regeneration) • Separate sexes (except a few hermaphrodites) • Fertilization usually external • Free swimming, bilateral larval stages

  8. Characteristics of EchinodermsWater vascular system • Allow them to move, obtain food, exchange gases and excretion • Parts: • 1) Sieve plate – water enters and leaves • 2) Ring canal – water flows into this from the sieve plate

  9. Characteristics of Echinoderms • Water Vascular system, cont. • Parts, cont.: • 3) Radial canal – each arm has one of these, connected to ring canal • 4) Ampulla – muscular sac that helps force water into a tube foot • 5) Tube foot – hollow tube with suction-cups on the end, helps with attachment, detachment Tube feet w/ moving sea star

  10. Characteristics of Echinoderms • Complete digestive system • Circulatory system (Blood-vascular or hemal) is reduced in size • Respiration • Dermal branchiae • Tube feet • Respiratory trees or bursae • NO Excretory organs

  11. Characteristics of Echinoderms • Nervous system • No head or brain • Few specialized sensory organs • Do contain a few sense receptors, photoreceptors (light), and chemoreceptors • Ocelli at tips of arms • Senses include touch, temperature, chemicals and light

  12. Classification • Class Asteroidea • 1500 living species • Found on shorelines near rocks or near sandy/muddy bottoms among coral reefs • Brightly colored • Range in size from centimeter across to almost 3 feet across • Many are carnivorous (eat other animals – like mollusks, other echinoderms, small fish) • Ex: sea stars, starfish, pea star, leather star

  13. Classification • Class Ophiuroidea • 2000 living species • Found in ocean bottoms (benthic), marine areas • Very secretive animals where little to no light penetrates • Ex: brittle stars

  14. Classification • Class Echinoidea • 950 living species • Found in all sea areas (intertidal regions to deep ocean bottoms) • Lack arms, very brightly colored, some contain toxins • Ex: sea urchins, sand dollars, heart urchins

  15. Classification • Class Holothuroidea • 1150 living species • Found in all sea areas (intertidal regions to deep ocean bottoms) • Some crawl, others found beneath rocks, other burrow • Elongated bodies, bodies are soft • Ex: sea cucumbers

  16. Classification • Class Crinoidea • 625 living species • Found in all sea areas (intertidal regions to deep ocean bottoms) • Stay attached to ocean bottoms/rocks/coral most of their lives • Stiff, hardened bodies • Ex: sea lilies, feather stars

  17. Starfish Characteristics • General Characteristics • Radial symmetry • Contain five arms/rays • Each arm radiates out from a central disc • If an arm is lost/damaged, it can usually be regenerated.

  18. Starfish Characteristics • Contain a coelom • Water vascular system: • Use this to move, gather food, respiration and excrete wastes • Use tube feet (tiny podia that expel water) • Excretion: • Contain anus • Also use water vascular system

  19. Starfish Characteristics • General Characteristics, cont. • Digestion: • Contain mouth (on underside/ventral side of sea star) • Each arm is full of digestive glands (which digest food that enters mouth) • Contain a pyloric stomach (digests food) • Also contain cardiac stomach (which they can push OUT of body to engulf prey) • Intestines is SHORT (connects stomach to anus)

  20. Starfish Characteristics • Diet: • Clams, oysters, small fish, other arthropods, dead/decaying matter, coral, sponges, plankton • Reproduction: • Capable of both sexual and asexual reproduction • Separate sexes • External fertilization • Ecological importance: • Decoration • Bio-indicators (help us to determine how polluted water environments are)

  21. Dissection Starfish Video Dissection External and Internal

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