Transcript Cnidaria
RADIATAanimals with radial symmetry PHYLUM CNIDARIA • Cnidarians are animals with stinging tentacles BODY STRUCTURE • Radial symmetry • No organ systems • Nerve net (primitive nervous system) –Whole body responds no matter what was stimulated • Outer membrane, inner membrane and jelly middle called mesoglea –Oxygen diffuses right into its body, CO2 diffuses out BODY STRUCTURE • Have sensory organs –Statocysts…balance organ –Box jellies have 4 pairs of eyes See Fig 7.3 pg 126 Hydra BODY STRUCTURE • Primitive muscle cells- weak swimmers • Incomplete digestive tract- one opening for waste and food • Lack all other systems and no body cavity • Do have hormones to communicate between cells REPRODUCTION • Some Cnidarians have an alternation of generations, vary as to dominant stage • Medusa is the sexual body plan • Polyp is the asexual body plan • Larvae is called planula See Fig 7.2 pg 125 FEEDING • Cnidoblasts / nematocysts – stinging cells – Used in defense and to paralyze prey – After being triggered these cells cannot be reused so they must be regenerated • Planktonic version are carnivorous, sessile version are filter feeders • Food is digested in the cavity Cnidaria Taxonomy • Class Hydrozoa - Siphonophores • Class Anthozoa – Coral • Class Cubozoa - Box Jellies • Class Scyphazoa - Jellyfish Class Hydrazoa Portugeuse Man O War, Hydra Dominant phase is polyp Found as colonial animals or individuals Individuals of a colony cannot exist on their own Class Hydrazoa • Different polyps have different roles – Feeding polyps – Reproductive polyps – Special tentacle polyps – Float polyps Class Anthazoa • Sea Anemones – Live as a polyp attached to the substrate • Coral – Colonial polyps with a limestone exoskeleton – Polyps share a stomach – Feed on plankton and have symbiotic algae that live in their tissue and give them nutrition – Build reefs using Ca in the water and CO2 from their algae See Figs 7.24, 7.26 pg 138-39 A Zoantharian Coral Class Scyphazoa • Spend most of their life as umbrella shaped medusa • Size range from cms to meters across • Typical NJ jellies- moon, purple and lion’s mane jellyfish • Population explosions of 100s or 1000s of these animals is currently a concern • Major predators include tuna, swordfish, moonfish, triggerfish and certain kinds of sea turtles Aurelia Moon jellyfish, Aurelia Fig 7.16, 17 pg 134 Pelagia Cyanea Class Cubazoa • More square shaped than regular jellies • Powerful stings that can kill a human • Good swimmers Ecology • • • • Important predators Corals are most diverse places in the ocean Important food source for some animals Huge blooms are occurring recently because of warming ocean temperatures (??) or because of overfishing (???) Treatment of Stings • minimize the number of nematocysts discharging into the skin • remove the tentacles that adhere to the skin by using sand, clothing, towels, seaweed • meat tenderizer, sugar, vinegar, plant juices and sodium bicarbonate have all been used with varying degrees of success. • Do not use : Methylated spirits, picric acid and human urine http://en.wikipedia.org/wiki/Image:Haeckel_Ctenophorae.jpg Phylum Ctenophora • Common name….comb jellies • Unique Characteristics – Comb plates (not tentacles) – Medusa stage only – Luminescence common – Position of paired tentacles changes symmetry to biradial Ecology • Form a large percent of the plankton • Can regenerate depending on damage • Feed on plankton including: larvae, worms, jellyfish, other comb jellies, and sometimes small fish. • Same predators as jelly group Image ID: nur01002, National Undersearch Research Program (NURP) Collection Credit: OAR/National Undersea Research Program (NURP) Difference From Cnidaria – No alternation of generations (medusa only) – No nematocysts have sticky cells instead – Biradial symmetry, two tentacles – Combs not tentacles – Complete digestive system Comparison Ctenophora to Cnidaria • Similarities –Nerve net –Lack of organ systems –Similar role in marine oceans Taxonomy Phylum Ctenophora See Fig 7.28 pg 140 Ctenophoran Comb Jelly t Fig 7.28 pg 140 Ctenophore Comb Jelly See Fig 7.28 pg 141 Ctenophoran Comb Jelly Fig. 7.28