2 4 Classes of Phylum Cnidaria HYDROZOA – Obelia, Hydra (above), Portuguese Man O WarSCHYPHOZOA - JellyfishCUBOZOA – 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 mesogleaExhibit radial symmetryPossess tentacles used in transportation and for capturing food and stinging cells called nematocysts.Possess a Gastrovascular Cavity (GVC)Primitive Nervous SystemHermaphroditic : can reproduce sexually (do not self fertilize) or asexually by regeneration or buddingHave a motile (medusa) and a sessile (polyp) stage in their livesFound 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 specializedTentacleGastrovascular CavityMouth and AnusCalcified Shell (Coral)Note: This diagram shows the GVC in the polyp body type.
5 2 Body Types Present in Phylum Cnidaria PolypSessile (no movement as they are anchored to the ground)Tentacles face upasexualEx. Hydra, sea anemones, coralMedusaMotileTentacles face downsexualEx. Jellyfish, sea wasps
7 The stinging cells: Nematocysts Nematocysts are most commonly located at the end of tentaclesAre composed of special cells called cnidocytes that have special organelles (cnidocysts) that produce a toxinWhen 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 preyA 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 medusaThe 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 polypThis alternating between two life forms is termed ALTERNATION OF GENERATIONS
9 Brooding AnemonesFrom 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 waterForm symbiotic relationships with other ocean lifeExamples.Clownfish and anemone (remember Finding Nemo?)Coral and many types of algaeCoral will die as the water temperature increases. Death of coral often precedes death of entire ecosystemsThe 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’ WarLooks like a jellyfish but is actually a colony of specialized polyps and medusasThe sting from their tentacles causes excruciating pain and sometimes deathNamed for its air bladder which looks like the sails of a Portuguese fighting shipSuper cool fact: Loggerhead turtles are actually immune to their toxins and feed on the Portuguese Man O’ WarPortuguese 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 deathIn Nov. – April they are abundant in Australian waters but it is not known where they go for the winterThrough ultrasonic tagging it has been found that they sleep on the ocean floor between 3pm and dawn to conserve energy and avoid predatorsPossess 22 very simple light sensing eyes as well as a more developed eye 0.1 mm acrossBox Jellyfish Chironex fleckerThis jellyfish has had an ultrasonic tag attached (very carefully!) to it in order to help learn more about the migration patterns of these cnidarians