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Cnidarians

Cnidarians. Stinging Creatures. Also known as coelenterates. Includes jellyfish, sea anemones, hydra, coral The common characteristic is that they have stinging cells called cnidocytes located on tentacles. Cnidocyts contain threadlike stingers called nematocysts.

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Cnidarians

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  1. Cnidarians Stinging Creatures

  2. Also known as coelenterates. • Includes jellyfish, sea anemones, hydra, coral • The common characteristic is that they have stinging cells called cnidocytes located on tentacles. Cnidocyts contain threadlike stingers called nematocysts. • They are in the Animal kingdom so they are multicellular and heterotrophic. • About 9000 species.

  3. Radially symmetrical • Have tissues • Some are solitary and some are colonial.

  4. Body forms There are 2 basic forms of cnidarians. A. Medusa Mouth and tentacles are pointed down as in a jellyfish.

  5. B. Polyp The mouth and tentacles face upward. Other side is usually attached at the basal disk.

  6. Structure • Soft bodies with tentacles that surround a mouth, the only opening. • There are 2 cell layers. The outer layer is the ectoderm and the inner layer is the endoderm or gastroderm. • Between the 2 layers is the jellylike mesoglea. • Inside, there is a body cavity called the gastrovascular cavity • Cnidocytes line the tentacles. • In the cnidocytes are the nematocysts.

  7. Does Peeing on a Jellyfish Sting Actually Help? | Mental Floss • jellyfish stings - Google Search

  8. Movement • 1.float and rely on ocean currents • 2.Jet propulsion using water. The nerve net sends a message to muscles to force water out of a series of canals and out of the bottom. Tentacles have nothing to do with swimming.

  9. Circulation and Respiration • No special structures. No heart. No lungs. No gills. No blood. • Oxygen is easily absorbed through their thin body. • Food is absorbed by the ectoderm (gastrodermis).

  10. Nutrition and Digestion • No special structures. • Food is drawn into the mouth through currents. Enzymes in the gastrovascular cavity digest it. It is absorbed by the endoderm, transferred through the mesoglea and absorbed by the ectoderm. • Wastes leave through the single opening, the mouth. • Tentacles with stinging cells help get food. They are armed with stingers and poison.

  11. Nervous system • No brain • They have a nerve net which sends messages throughout the body. • They have more of a general reaction rather than a specific reaction.

  12. Excretion • Mouth and anus are one.

  13. Corals and Sea Anemones (Anthozoa) • Sea anemones are found in coastal areas and attach themselves to rocks. • Anemones feed on fishes except for the clown fish. They have a mutualistic relationship. The clownfish drives away fish that may feed on the anemone and the anemone protects the clownfish. Clownfish and Sea Anemones – YouTube • Symbiosis & Anemonefish - Reef Life of the Andaman - Part 18 - YouTube • Carnivore • Considered immortal What makes sea anemones immortal? • Killer Sea Anemone attacks poor crab - YouTube

  14. Corals Corals are polyps that live in colonies.

  15. Skeleton • Coral create a limestone base. • Polyps have a basal disk that creates a chemical to cement them to an object. • As the polyps die, their skeleton remains and new polyps form. Eventually, a coral reef is formed. • Form in shallow, warm water near the equator.

  16. Some coral have a symbiotic relationship with algae. The photosynthetic algae make food for the coral and they give the algae a place to live. • (mutualism=both benefit)

  17. Learn360 - Play Video - Coral Reefs of Indonesia Learn360 - Play Video - Coral Reefs

  18. Jellyfish (Scyphozoa) • Means cup animals. • The dominant form of life is the medusa. • Range from 2cm to 13 feet.

  19. Reproduction • Alternation of generations. What’s that? • The image you have of a jellyfish is an adult. Males release sperm into the water. They enter the mouth of the female and fertilize the eggs. • The fertilized egg becomes a larva called a planula. It leaves the female and settles down and forms a polyp.

  20. Reproduction (cont) • The polyp grows into a colony and buds off medusas which become adult jellyfish. • The first part was sexual and the budding was asexual.

  21. Giant Jellyfish Threaten Japan Fishing - CBS News Video • Australia's Box Jellyfish: Most Venomous Animal in the World – YouTube • World's Largest Jellyfish | North America - YouTube

  22. Hydra (Hydrozoa) • Hydras exist only as polyps. • Live in fresh water. • Can detach and somersault as a form of movement. • Hermaphrodites. Reproduce sexually in the fall. Sperm released directly into the water. • Can also reproduce asexually through budding.

  23. hydra catches water flea – YouTube • Budding In Hydra - YouTube

  24. Portugese man of war • Appears to be a single organism but is really a colony of medusas and polyps. • The purple gas filled float is made of polyps and floats on top of the water. • The tentacles are medusas and can extend 65 feet. • Video -- Portuguese Man-of-War -- National Geographic

  25. Importance • Yes, in some places (China), people eat jellyfish, raw or cooked. • Coral are extremely important in the ocean for protecting shoreline and as a habitat for other organisms. • Research and medicine. • Jewelry (coral) • Used to make concrete • Tourism

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