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Phylum Cnidaria Sea anemones, jellyfish, coral Approx. 10,000 species Mostly marine Radial symmetry Carnivorous Have a centrally located mouth surrounded by tentacles Mouth opens to a gut where food is digested Have only one opening that is used for both feeding and excretion Cnidaria The Basics Cnidarians get their name from the cnidocytes that are located along their tentacles These structures are used for defense and to capture prey Each cnidocyte contains a nematocyst, which is a poison-filled, stinging structure that contains a tightly coiled dart As prey brushes against the tentacles: Thousands of nematocysts explode into the animal Poison is injected and either paralyzes or kills the prey The prey is then brought to the mouth by the tentacles Cnidaria Cnidocytes and Nematocysts Cnidaria Cnidocytes and Nematocysts Polyp A sac-like attached stage with the mouth and tentacles oriented upward Anemones, coral Medusa An upside down polyp adapted for swimming Jellies Cnidaria Forms of Cnidarians Many consist of feathery or bushy colonies of tiny polyps Can be attached or motile The polyps can be specialized for feeding, defense, or reproduction Siphonophores are hydrozoans that form drifting colonies of polyps Some polyps may be specialized as floats, others form tentacles Ex – Portuguese Man of War Cnidaria Types of Cnidarians - Hydrozoans Tall Tubularia Herringbone Hydroid Clapper Hydromedusa Cross Jelly Portuguese Man of War Cnidaria - Hydrozoans Ringed Tubularia “True Jellies” Large medusa are the dominant life cycle Polyps are very small and release juvenile medusa Have a bell (rounded body) that can reach a diameter of 10 ft Swim with rhythmic contractions of the bell, but really rely on currents Some are extremely dangerous and their stings can be fatal Cnidaria Types of Cnidarians - Scyphozoans Moon Jelly White Spotted Jelly Helmet Jelly Blubber Jelly Lions Mane Jelly Oceanic Jelly Cnidaria - Scyphozoans Sea Nettle Solitary or colonial polyps that lack a medusa stage More complex than scyphozoans and hydrozoans The gut contains septa which increase surface area for digestion Septa also provide increased support allowing these organisms to grow larger All (except anemones) are asymmetrical Corals – mostly colonial; calcium carbonate skeleton Sea anemones – colorful; often have large polyps Gorgonians (sea fans) – colonial; secrete a tough branching skeleton made partially of protein Soft corals, sea pens, sea pansies – form fleshy colonies with large polyps and no hard skeletons Cnidaria Types of Cnidarians - Anthozoans Cup Coral Stony Coral Green Mushroom Coral Deepwater White Coral Red Mushroom Coral Sun Coral Brain Coral Cnidaria - Coral Cup Coral Green Anemones Beadlet Anemone Swimming Anemone Horseman Anemone Fireworks Anemone Banded Tube Anemone Cnidaria – Sea Anemones Green Anemone Orange Sea Fan Bali Blue Sea Fan Red Sea Fan with Polyps Cnidaria – Gorgonia Purple Sea Fan Cnidaria – Soft Coral Cnidaria – Sea Pens Cnidaria – Sea Pansies Box Jellies Most poisonous jellies Look similar to true jellies Main difference is their shape – from above, they have a box shape Faster moving than true jellies Have eyes Typically have 4 tentacles or 4 groups of tentacles 20 species Found in tropical and subtropical waters Cnidaria Types of Cnidarians - Cubazoans Cnidaria - Cubazoans Most are carnivorous Use tentacles to capture prey and bring to mouth where ingestion occurs Food passes into the gut where digestion occurs Initial phase of digestion is extracellular, meaning it takes place outside cells After initial digestion, the partially digested food enters into cells to complete digestion intercellularly Anything that can’t be digested exits the animal through the mouth Cnidaria Feeding and Digestion Rely on diffusion for all three of these processes Diffusion occurs within and between cells and through the body walls Cnidaria Respiration, Circulation, Excretion Cnidarians lack a brain or true nerves However, they do have specialized nerve cells that connect to form a nerve net Some medusa have primitive eyes and statocysts, which give a sense of balance Cnidaria Response Asexual by budding and fission Sexual Sexes are often separate Female Male releases eggs into water releases sperm into water External fertilization – fertilization takes place outside the body If species is a type of polyp, larvae will attach to a hard surface and develop into an adult If species is a medusa, larvae will continue to move as it develops Cnidaria Reproduction Cnidaria Fission and Budding Cnidaria Spawning Cnidarians: Life on the Move (15 min) http://www.shapeoflife.org/video/cnidari ans-life-move Cnidarians: Moon Jelly Life Cycle (3 min) http://www.shapeoflife.org/video/cnidari ans-moon-jelly-life-cycle Cnidaria Videos –
