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Download Chapter 8 Phylum Cnidaria
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Lecture Exam I • • • • Cambrian radiation / phylogeny = 2 papers Systematics intro Protista: 10 phyla Animalia: Porifera, Cnidaria • ~20 questions • Short answer, essay, life cycle sketch Phylum Cnidaria • 3 Classes: – Anthozoa – Scyphozoa – Hydrozoa Characteristics: • Diploblastic metazoan • Ectoderm and endoderm separated by acellular • mesoglea Nervous system: simple nerve net, neurons Development • Planula larvae • ciliated, motile, gastrula larva Radial symmetry • Modified into biradial, quadradial, etc… Gastrovascular cavity • Saclike, partitioned, or branched w/ one opening • = mouth and anus Alternating life history forms: polyp and medusa Polyp • Radial symmetry • Oral end = hypostome or manubrium in hydrozoans – flat pedal disc in anthozoans • Tentacles surround mouth Polyp Gastrovascular cavity • Circulation, digestion, distribution of nutrients • Hydrozoans: coelenteron is single tube • Scyphozoans: four longitudinal mesenteries • Anthozoans: compartmentalized by mesenteries Polyp: support • Hydrostatic, water-filled coelenteron • Anthozoans - bits of sediment and shell fragments in column wall for support • Hydrozoans - flexible horny perisac (periderm) of chitin from epidermis Polyp: movement • Retractor muscles: longitudinal fibers along mesenteries • Circular muscles: sphincters – in tentacles and oral disc • Most polyps sedentary or sessile • Creep slowly w/ pedal disc musculature • http://www.youtube.com/watch?v=UI531GMRTM Medusa • All cnidaria except Anthozoa • Bell-, dish- or umbrella-shaped • Exumbrella: convex upper (aboral) surface • Subumbrella: concave lower (oral) surface – Mouth at center Free-floating, mouth down Medusa • External surface: epidermis • Internal surface: gastrodermis • Coelenteron central; extends to radial canals – Usually four radial canals, tentacles, stomach divided by mesenteries into four gastric pouches Nematocysts • Stinging structures • Nematocysts: multiple types • Generic nematocyst (all) – Double-walled capsule w/ toxic mixture of phenols + proteins – Spines or barbs for penetration, anchor in victim • Spirocyst (Anthozoa) – Spring-like mechanism – Adhesive tubules wrap around and stick to victim • Ptychocyst (tube anemones) – Create capsule tubule Feeding and digestion Tentacles capture prey, carry to mouth, ingest whole Extracellular digestion in coelenteron – enzyme-producing cells Reproduction and Development Hydrozoa • Polyps = asexual budding Reproduction and Development Hydrozoan • Free-living hydromedusa • Dioecious, release sperm or eggs Reproduction and Development Scyphozoa • Asexual reproduction: small polyp = scyphistoma • Medusa from scyphistoma • Immature medusa = ephyra • Most species dioecious Reproduction and Development Anthozoa • Exclusively polyps • Asexual reproduction • Fission • Pedal laceration: pedal disc spreads, anemone moves, leaves small fragments – develop into adult Class Hydrozoa Hydroids and hydromedusa Hydrozoa Portuguese Man-of-war Physalia Class Anthozoa Anemones, corals, sea pens Exclusively marine Octocorals • Soft corals – – – – – – Gastraxonacea Helioporaceans Sea pens and sea pansies Protoalcyonaria Stoloniferans Telestaceans Sea pen Class Anthozoa Anemones and true corals • True sea anemones • True corals (stony corals) Class Anthozoa • Black or thorny corals • Ceranthids or tube anemones Class Scyphozoa • Jellyfish Box jelly Chiropsalmus
