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Cnidarians

Cnidarians. “ The guys with the stinging tentacles ”. Cnidarians. Finally, we see a pie that can be sliced! Cnidarians actually exhibit radial symmetry in which similar body parts can be grouped around a central axis.

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Cnidarians

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  1. Cnidarians “The guys with the stinging tentacles”

  2. Cnidarians • Finally, we see a pie that can be sliced! • Cnidarians actually exhibit radial symmetry in which similar body parts can be grouped around a central axis. • Here we also observe a large jump on the evolutionary scale: tissues that perform specific functions.

  3. Phylum Cnidaria The Classes of Cnidaria are: • Anthozoa- Sea Anemones and Corals • Hydrozoa- Hydra • Scyphozoa- “true”jellyfish • Cubozoa- “box-shaped” jellyfish • Ctenophora- non stinging Cnidarians: • Comb Jellies **There are over 10,000 species of Cnidarians

  4. All About Cnidarians

  5. Interesting Stuff 1. Jellyfish fact: Jellyfish have been around for more than 650 million years which means that they outdate the dinosaurs and the sharks. 2. Jellyfish fact: Different species of jellyfish can be found in all the worlds’ oceans. Jellyfish can even be found in freshwater. 3. Jellyfish fact: A species of jellyfish, the Box jellyfish (sea wasp) kills more people than any other marine creature. 4. Jellyfish fact: The worlds largest known jellyfish can reach a diameter of 2.5 m/ 8ft and their tentacles can grow to be half the length of a football field. 5. Jellyfish fact: Jellyfishes uses jet propulsion to make their way through to oceans of the world. Some swim while others mostly drifts with the currents. 6. Jellyfish fact: Some species of jellyfish contain a lot of protein and are thought to be able to play a large role in ending hunger and malnutrition.7. Jellyfish fact: Jellyfish is able to reproduce both sexually and asexually during different parts of their lifecycles8. Jellyfish fact: what enables them to survive is their stinging tentacles that protect them from being preyed upon.

  6. Characteristics of Cnidarians • Two cell layers (epidermis, gastrodermis, separated by jelly-like layer called mesoglea) • Stinging tentacles • Sac-like digestive system • Radial symmetry • Tentacles are arranged in a circle around the mouth • Nerve net- simple nervous system • invertebrate

  7. Radial Symmetry Radial Compass jellyfish

  8. Anatomy A. Polymorphism- Cnidarians have more than one body form: 1. Polyp 2. Medusa

  9. Polyp Form • Tube with tentacles around the mouth • Sessile Coral polyp

  10. Polyp (sea anemone)

  11. Polyp (Hydra)

  12. Medusa • Umbrella shape • Tentacles around mouth • Motile, Free-swimming

  13. Cnidocytes-Stinging Cells • Within the cnidocyteis the nematocyst (which is like a capsule) • The capsule has the stinging structure which is a hollow thread (Filament) with barbs • Most contain a toxin • Very small, but discharged in large numbers • Usually the sting is only strong enough to kill zooplankton or tiny fish • But there are exceptions!

  14. Discharged nematocysts, • stinging cells used for defense and prey capture, have been the plague of more than fish. • Stings from certain jellyfish have resulted in death in a matter of hours, especially for infants.

  15. Habitat Aquatic: • Most are Marine • A few are freshwater

  16. Two Tissue Layers 1. EPIDERMIS – OUTER LAYER 2. GASTRODERMIS – STOMACH CAVITY MESOGLEA – JELLY MATERIAL BETWEEN TISSUE LAYERS ABUNDANT IN JELLYFISH TO HELP THEM FLOAT

  17. One Opening System WASTES, GAMETES OUT FOOD IN Food enters through the mouth and is digested in thee cells. Wastes are excreted through the mouth. Sperm and eggs are released through the mouth.

  18. Feeding 1. Carnivores (predators) 2. Process of feeding a. Tentacles sting prey with nematocysts b. Tentacles grab prey c. Prey pulled into mouth 3. Prey moved into gastro-vascular cavity (GVC)* 4. GVC makes enzymes, breaks down food, extra-cellular digestion 5. Undigested food moves back out of mouth Lion’s mane eats another jelly!

  19. Process of feeding 3. Prey stuffed into gastro-vascular cavity (GVC)* 4. GVC makes enzymes, extra-cellular digestion 5. Undigested food back out mouth *incomplete digestive tract (no anus)

  20. Lion’s mane jellyfish eating

  21. Respiration • Via diffusion • Body is two cell layers thick

  22. Response • No nervous system • No brain • Nerve net around mouth • Nerves cover the body but do not tell the difference between body parts.

  23. Locomotion • Medusa- motile, free-swimming • Polyps- sessile,attached to hard substrate Exceptions: 1. Hydra tumbles on tentacles 2. Sea anemones glide on pedal disc

  24. Reproduction 1. Asexual budding 2. Sexual a. Medusae release sperm & eggs b. Larvae are free-swimming

  25. Life Cycle of a Typical Cnidarian • Alternation of Generations • One form is the polyp (a cylinder with the closed end attached to the substrate and the open end with the mouth and tentacles directed upward) • The other form is the medusa, free-swimming, with the mouth underneath (like a jellyfish)

  26. Hermaphrodite sexual Life Cycle of a Typical Cnidarian asexual Alternation of Generations

  27. Ecological Role • Predators and prey • Neurotoxins in medical research • Coral – jewelry, building, reefs (surfing!) • Coral reefs - habitat for many different species, great biodiversity, protect coastline E. Symbiosis with other organisms

  28. Do Now • Explain how the jellyfish is adapted for floating? • How do jellyfish capture and digest their prey? • Describe how a typical jellyfish reproduces. • How does the adult form of a jellyfish differ from that of a sea anemone? • How does a sea anemone obtain its food? • How does the sea anemone respond to stimuli?

  29. Class Anthozoa: Sea Anemones

  30. Class Anthozoa: Corals

  31. FORMATION OF CORAL REEFS CORAL REEFS ARE BUILT BY MILLIONS OF CORAL POLYPS OVER THOUSANDS OF YEARS EACH POLYP CREATES A “CUP” OF CALCIUM CARBONATE TO LIVE IN CORALS REPRODUCE ASEXUALLY BY BUDDING, THIS PROCESS HELPS COLONIES TO GROW POLYPS ARE CONNECTED OLD SKELETONS

  32. FORMATION OF CORAL REEFS CORALS ALSO REPRODUCE SEXUALLY ONCE A YEAR BY RELEASING SEX CELLS INTO THE WATER. THIS HELPS TOP ESTABLISH NEW COLONIES

  33. HARD CORALS REEF BUILDERS – USE CALCIUM FOR SKELETON EACH SPECIES HAS A UNIQUE COLONY & CUP DESIGN EXAMPLES: BRAIN, ELKHORN, STAR

  34. Class Scyphozoa: True Jellyfish Fried egg jelly

  35. Giant Jelly off Coast of Japan

  36. Remember you can only touch the tops!!!

  37. Jellyfish Humor

  38. Portuguese Man 0’ War(a Hydrozoan), NOT a true jelly fish

  39. Portuguese Man 0’ War Tentacles of Physalia physalis

  40. Chironex fleckerithe Box jelly fish

  41. Carukia barnesi: the badest of the bad! Irukandji syndrome: A sting from this little guy can cause the following: “It begins with a mild sting, followed by severe lower back pain, muscle cramps in arms, legs, stomach and chest. It causes sweating, anxiety, nausea, vomiting, headaches and palpitations, and has also been known to cause cardiac failure.”

  42. Portuguese Man o’ War vs. Box Jelly fish

  43. COMB JELLIES PHYLUM CTENOPHORA BASIC CHARACTERISTICS: “CTEN” REFERS TO FUSED PLATES OF CILIA LOOK LIKE A “COMB” STRUCTURE DO NOT CONTAIN STINGING CELLS USE CILIA TO FILTER WATER TENTACLES ARE STICKY TO CATCH FOOD

  44. Comb jellies: Ctenophora Similar to cnidarians in most respects. Nearly 100 species. Contain cilliary combs which assist in prey capture and mobility.

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