Transcript Cnidaria
Cnidaria Classification JELLYFISH Kingdom Animalia Phylum Cnidaria Class Scyphozoa – larger jellyfish Class Hydrozoa – floating colonies, Portuguese man-ofwar Characteristics Up to 99% water, often less than 5% solid organic matter found all over the world , in all types of seas, even freshwater; found at all depths Characteristics range in size from 1 inch (Caribbean jelly) to the (Arctic Lion’s Mane) with tentacles as long as 100 ft. More complex than sponges, not as complex as marine worms Arctic Lion’s Mane Presence of specialized tissues that make it possible to swim, respond to external stimulus (light, smell) and engulf prey; possess an elementary nervous system or nerve net. Simple digestive cavity which acts as a gullet, stomach, and intestine w/one opening for the mouth and anus Most are found in the medusa form – gas filled domed bell Have a centrally located mouth surrounded by tentacles used to capture and handle food; have 4 to 8 oral arms near the mouth, used to transport food to mouth that is captured by tentacles Has radial symmetry, allows jelly to respond to food or danger from any direction Have nematocysts on tentacles and/or oral arms to string/stun prey A single tentacle can have hundreds or thousands or nematocysts embedded in the epidermis Have 2 layers, an epidermis and gastrodermis with a thick, elastic jellylike substance (mesoglea) in between that expands to form the domed bell Most jellyfish have a short lifespan and may live for only a few weeks, average lifespan 3 to 6 months Feed on small plankton type animals and small fish; larger species capable of eating large crustaceans Jellyfish are preyed upon by certain fish (spadefish, sunfish) and loggerhead turtles; Both fresh and pickled mushroom jelly are eaten as a delicacy in China and Japan Locomotion – most drift with the currents with little control over their horizontal movement; there is some ability to navigate vertically some swim with rhythmic contractions of the bell; because jellyfish are sensitive to light, vertical movement is important to descend to deeper depths during the day Some have bioluminescence Defense – transparency helps to reduce silhouette nematocycts Sea wasp found in Australia, SE Asia, and Indian ocean has been know to cause death in human Reproduction Are either male or female and reproduce sexually. The reproductive organs (gonads) develop in the lining of the gut. During reproduction the male releases sperm through its mouth into the water column. Sperm swims into mouth of female where fertilization occurs. The larva is, either ‘brooded’ within the gut of the adult or develops as a free-swimming planula (larva w/ cilia). The planula seek a shaded surface and attaches itself onto a substrate and develops into a polyp. These polyps divide and bud into a young jellyfish (ephyra). In a few weeks, and ephyra will grow into an adult medusa. Treatment of a Sting Meat tenderizer, sugar, vinegar, plant juices and sodium bicarbonate have all been used with varying degrees of success. Methylated spirits and other forms of alcohol formerly recommended for inhibiting stinging cells actually stimulate them and may increase pain and cause severe skin reactions. Picric acid and human urine also cause a discharge of nematocysts and should not be used.