http://fotokudra.lt/files/I261542.jpg General Characteristics • The name Cnidaria comes from the Greek word "cnidos," which means stinging nettle • They have stinging cells called nematocysts • An exclusively aquatic phylum • Tissue level organization • Generally, their bodies are two cell layers thick • Radial symmetry; Little specialization; Pseudocoelomate • Extracellular digestion • Hydrostatic skeleton • Both asexual and sexual reproduction • External fertilization • One opening, the mouth
http://www.biology.iastate.edu/Courses/211L/Cnidar/%20CnidINDX.htmhttp://www.biology.iastate.edu/Courses/211L/Cnidar/%20CnidINDX.htm http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb5pg3_files/hydra3.jpg http://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Cnidaria/Class-Hydrozoa/HydroidPolyps/Obelia_dichotoma.html Class Hydrozoa (Hydroids) Hydra Obelia Goneonemus
http://seanet.stanford.edu/HydroScyphozoa/aurelia_lab580.jpg Class Scyphozoa (Jellyfish) Aurelia
http://www.valdosta.edu/~jlgoble/Sea%20Anemone%20Diadumene%20Dia%2030cm%201.JPGhttp://www.valdosta.edu/~jlgoble/Sea%20Anemone%20Diadumene%20Dia%2030cm%201.JPG Class Anthozoa (Corals & Sea Anemone) Sea Anemone
http://thestashbox.files.wordpress.com/2009/02/226boxjellyfish1.jpghttp://thestashbox.files.wordpress.com/2009/02/226boxjellyfish1.jpg Class Cubomedusa (Box Jellyfish) Box Jelly
Body Plan • Tissue level of organization • Outer covering (epidermis), inner gasterodermis, non-cellular mesoglea between the two; Diploblastic, body and tentacles consists of two cell layers • Possess stinging structures, nematocysts, housed in cells called cnidocytes; Single body opening, the mouth • Radial symmetry • Two body forms • Polyp: cylindrical with tentacles at one end; Sessile (non-motile) but some capable of locomotion; mouth points upward; EX: The Hydra • Medusa: Free swimming; Bell shaped; Swim by undulations of their bell; Thicker mesoglea mouth-side down; EX: The Jellyfish • Some cnidarians exist only in polypoid or medusoid form, others alternate between the two • Both diploid so not true alternation of generations
http://biology.unm.edu/ccouncil/Biology_203/Images/SimpleAnimals/cnidariaDiagram.jpeghttp://biology.unm.edu/ccouncil/Biology_203/Images/SimpleAnimals/cnidariaDiagram.jpeg Body Plan cont.
http://www.arcodiv.org/cnidarians.html Feeding http://www.nick.com/multimedia/binits08games/spongebob-jellyfishin-game.png http://www.nick.com/multimedia/binits08games/spongebob-jellyfishin-game.png • Carnivorous or filter feeders • Medusa do not hunt for prey, use “sit-and-trap” method • Uses cnidae and toxins to stun and kill prey • Sessile ployps depend on organisms that come in contact with tentacles • Tentacles have stinging cells (cnidocytes) that contain small harpoons called nematocysts • Harpoon propelled by osmotic pressure, spears prey and draws it back to hydra • Both have a ring of tentacles around the mouth • Extracellular digestion; gut cavity for digestion, lining cells engulf food by phagocytosis • Enzymes secreted from the gastrodermis break down the food
http://www.arcodiv.org/cnidarians.html Respiration • Contains no respiratory system This image depicts the internal structure of a jellyfish (a Medusae cnidaria). Because the great majority of cells are directly in contact with the ocean water, a complicated respiratory system is not needed.
http://www.connecticutvalleybiological.com/images/vc1336v.jpghttp://www.connecticutvalleybiological.com/images/vc1336v.jpg Circulation • No circulatory system (blood vessels) • Majority of cells come in direct contact of seawater • Have gastrovascular cavity; inner cells exposed to water • Only two cell layers thick, all cells exposed to water for nutrient and gas exchange
http://www.arcodiv.org/cnidarians.html Excretion • Contains no excretory organs • Gastrovascular cavity serves for gas exchange and digestion • Gas exchange takes place directly across the surface of their body and waste is released either through their gastrovascular cavity or by diffusion through their skin • No anus • Excretes through mouth, only opening
http://www.arcodiv.org/cnidarians.html Response • Simple net like nervous system • Coordinates contraction of muscles; Little central control
http://www.aboutmyplanet.com/files/2008/12/800px-Jellyfish_in_the_Montery_Bay_Aquarium-resized.jpghttp://www.aboutmyplanet.com/files/2008/12/800px-Jellyfish_in_the_Montery_Bay_Aquarium-resized.jpg Movement • Polyp • Sits on basal disk, used to glide around with help of mucus secretions • Some can somersault, bending over and attaching itself to substrate by its tentacles and looping over to new location • If polyp detaches itself from substrate, it can float to surface • Medusae • Outer layer, epithelium, contains specialized epitheliomuscular cells, each can contract individually • These cells form muscular rings around the bell shape of the jellyfish; allows the animal to propel through water
Reproduction • Polyps reproduce asexually (budding and fragmentation) • Medusae reproduce sexually • Fertilization external • Alternation between medusa, sexually reproductive stage, and polyp, the asexual stage • Class Anthozoa has no medusa stage • Medusae has a distinct larval stage which is planktonic; called planulae; multicellular, pear-shaped, entirely ciliated • Jellyfish have separate male and females • Medusae stage is dominant • Some exhibit the medusa form throughout their life while others first pass through other phases before maturing into the medusa form
Works Cited • "Introduction to Cnidaria." UCMP - University of California Museum of Paleontology. Web. 15 Apr. 2010. <http://www.ucmp.berkeley.edu/cnidaria/cnidaria.html>. • "Cnidarians." W. Fielding Rubel School of Business: Bellarmine University. Web. 16 Apr. 2010. <http://cas.bellarmine.edu/tietjen/images/cnidarians.htm>. • "The Anemones, Corals and Jellyfish (Phylum Cnidaria)." The Earth Life Web. Web. 19 Apr. 2010. <http://www.earthlife.net/inverts/cnidaria.html>. • Klappenbach, Laura. "Diet - Cnidarian Diet and Eating Habits." Animals Wildlife - Animal Facts, Animal Pictures, Habitat Facts, Evolution and Zoology. Web. 20 Apr. 2010. <http://animals.about.com/od/cnidarians/ss/cnidarians_6.htm>. • "The Noncoelomate Animals." Biology. Sixth ed. Boston: McGraw Hill, 2002. 886-89. Print.
Works Cited (Pictures) • "Multi-cell Organisms." A Review of the Universe. Web. 16 Apr. 2010. <http://universe-review.ca/F10-multicell.htm#Index>. • "Simple Animals." Web. 19 Apr. 2010. <http://biology.unm.edu/ccouncil/Biology_203/Summaries/SimpleAnimals.htm>. • "New Page 1." Virtual Microscope Home Page. Web. 19 Apr. 2010. <http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb5pg3.htm>. • "Obelia Dichotoma." WWU: On Campus. Web. 19 Apr. 2010. <http://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Cnidaria/Class-Hydrozoa/HydroidPolyps/Obelia_dichotoma.html>. • "Gonionemus." Biology Program at ISU. Web. 19 Apr. 2010. <http://www.biology.iastate.edu/Courses/211L/Cnidar/%20CnidINDX.htm>. • "Hydrozoa & Scyphozoa." SeaNet. Web. 19 Apr. 2010. <http://seanet.stanford.edu/HydroScyphozoa/index.html>. • "Search Results | SpongeBob.com." SpongeBob.com | SpongeBob SquarePants Episodes, Games, & Pictures. Web. 20 Apr. 2010. <http://spongebob.nick.com/search/game/spongebob%20games/0>. • "Anemone." Valdosta State University. Web. 19 Apr. 2010. <http://www.valdosta.edu/~jlgoble/topic.html>. • "Foto KÅ«dra - Fotografija - Cnidaria Scyphozoa II." FotoKÅ«dra - Fotografija | KÅ«ryba | Bendravimas. Web. 20 Apr. 2010. <http://fotokudra.lt/img.php?img=182032&nav=cat&page=156>. • "Jellyfish Take Over Ocean: A Dangerous Warning Sign." Go Green. Web. 20 Apr. 2010. <http://www.aboutmyplanet.com/green-news/jellyfish-ocean/>. • Hopcroft, Russ. "Cnidarians - Jellyfish and Kin." Arctic Ocean Diversity. Census of Marine Life, 4 Jan. 2008. Web. 20 Apr. 2010. <http://www.arcodiv.org/cnidarians.html>