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Phylum Cnidaria Cnidos = “Stinging Needle”

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Presentation on theme: "Phylum Cnidaria Cnidos = “Stinging Needle”"— Presentation transcript:

1 Phylum Cnidaria Cnidos = “Stinging Needle”

2 4 Classes of Phylum Cnidaria
HYDROZOA – Obelia, Hydra (above), Portuguese Man O War SCHYPHOZOA - Jellyfish CUBOZOA – box jellies (sea wasps) ANTHOZOA – anemones (above), corals, sea fans

3 Identifying Characteristics of the members of Phylum Cnidaria
Non-coelomates & therefore do not possess any true body systems or organs. 3 germ layers include ectoderm (protection), endoderm (inner lining) and mesoglea Exhibit radial symmetry Possess tentacles used in transportation and for capturing food and stinging cells called nematocysts. Possess a Gastrovascular Cavity (GVC) Primitive Nervous System Hermaphroditic : can reproduce sexually (do not self fertilize) or asexually by regeneration or budding Have a motile (medusa) and a sessile (polyp) stage in their lives Found in marine habitats

4 Gastrovascular Cavity (GVC)
The inner cavity responsible for digestion, circulation, respiration and excretion. Disadvantages of having a GVC include: There is only one opening….. The mouth is the anus….. Body systems of digestion, circulation, respiration and excretion are not separated or specialized Tentacle Gastrovascular Cavity Mouth and Anus Calcified Shell (Coral) Note: This diagram shows the GVC in the polyp body type.

5 2 Body Types Present in Phylum Cnidaria
Polyp Sessile (no movement as they are anchored to the ground) Tentacles face up asexual Ex. Hydra, sea anemones, coral Medusa Motile Tentacles face down sexual Ex. Jellyfish, sea wasps


7 The stinging cells: Nematocysts
Nematocysts are most commonly located at the end of tentacles Are composed of special cells called cnidocytes that have special organelles (cnidocysts) that produce a toxin When a trigger is stimulated it releases a barbed needle that penetrates the flesh and injects toxins. Nematocysts are used to ward off predators or attack prey A discharged nematocyst

8 Life cycle of a typical Jellyfish
#1-10 exhibit the formation of the polyp life form. #11 shows the polyp undergoing asexual reproduction in the form of budding. The top of the polyp breaks off and goes on to form the medusa stage of the jellyfish’s life. (if this was an anemone the polyp would settle on the ocean floor and become a new polyp…. See picture of brooding anemone on next slide) #12-14 shows the formation of the adult medusa The medusa will then go on to produce and release egg and sperm into the water. The eggs will be cross fertilized by the sperm of another medusa and eventually develop into a new polyp This alternating between two life forms is termed ALTERNATION OF GENERATIONS

9 Brooding Anemones From a single anemone other polyps are forming which will eventually break off and settle on the ocean floor to form new anemones. This is why many of the same type of anemone are often observed in the same area as the new polyps are not capable of traveling far distances.

10 Ecological Importance of Cnidarians
Filter and clean the water Form symbiotic relationships with other ocean life Examples. Clownfish and anemone (remember Finding Nemo?) Coral and many types of algae Coral will die as the water temperature increases. Death of coral often precedes death of entire ecosystems The clownfish are immune to the stinging cells of the clownfish anemone. Therefore the anemone provides protection and shelter for the clownfish and in turn the clownfish clean the anemone.

11 Super Cool Killer Cnidarians
The Portuguese Man O’ War Looks like a jellyfish but is actually a colony of specialized polyps and medusas The sting from their tentacles causes excruciating pain and sometimes death Named for its air bladder which looks like the sails of a Portuguese fighting ship Super cool fact: Loggerhead turtles are actually immune to their toxins and feed on the Portuguese Man O’ War Portuguese Man O’ War Physalia physalis

12 A common sign to observe near Australian Beaches

13 Box Jellyfish Chironex flecker
Possess the most deadly venom (toxins) in the animal kingdom which cause anaphylaxis shock and death In Nov. – April they are abundant in Australian waters but it is not known where they go for the winter Through ultrasonic tagging it has been found that they sleep on the ocean floor between 3pm and dawn to conserve energy and avoid predators Possess 22 very simple light sensing eyes as well as a more developed eye 0.1 mm across Box Jellyfish Chironex flecker This jellyfish has had an ultrasonic tag attached (very carefully!) to it in order to help learn more about the migration patterns of these cnidarians


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