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9/20/2011 Radiate Animals Phylum Cnidaria >9,000 species fossils >700 mya specialized cells (cnidocytes) specialized stinging organelle, the nematocyst Phylum Ctenophora <100 species comb jellies/sea walnuts Multicellular (metazoa) Unicellular (acellular) protozoan protists Poorly defined tissue layers Porifera Placozoa Uncertain Priapulida Chaetognatha Gastrotricha Entoprocta Loricifera Diploblastic Triploblastic Cnidaria Ctenophora Acoelomate Coelomate Rotifera Platyhelminthes Nematoda Rhynchocoela (Nemertea) Mesozoa Gnathostomulida Protostomes Annelida Mollusca Arthropoda Onychophora Pentastomida Pogonophora Sipuncula Echiura Pseudocoelomate Kinorhyncha Acanthocephala Nematomorpha Uncertain (misfits) Brachiopoda Phoronida Bryozoa Deuterostomes Echinodermata Hemichordata Chordata 1 9/20/2011 Cnidarian Characteristics 1) diploblastic: two well-defined germ layers: ectoderm & endoderm mesoderm may be derived from ectoderm (ectomesoderm) 2) internal body cavity: the gastrovascular cavity 3) extracellular digestion occurs in the gastrovascular cavity; gastrodermal cells enzymes for cellular digestion 4) nerve cells; nerve net but no central nervous system 5) sense organs: statocysts & ocelli 6) locomotion by muscular contraction : outer longitudinal & inner circular 7) unique feature: nematocysts (epidermis/gastrodermis) 8) tentacles: extensible projections for food capture with abundant nematocysts 9) all aquatic/mostly marine shallow marine environments some fresh water none terrestrial 10) some symbiotically e.g. with algae in reef-building corals 11) radial symmetry: oral & aboral ends 12) dimorphism: free-swimming medusae & sessile polyps: ecological niches 13) some: exoskeleton or endoskeleton: chitinous, calcareous or protein 14) gastrovascular cavity: a single opening serving as both mouth & anus 15) reproduction: either asexual or sexual 16) planula larva may be present 17) no excretory or respiratory system 18) no coelomic cavity 2 9/20/2011 Five Classes I. Hydrozoa Ectopleura Hydra: freshwater species no medusa stage budding Corymorpha Hydroids 3 9/20/2011 Polymorphism 4 9/20/2011 Craspedacusta freshwater hydrozoan Portuguese Man of War Physalia physalis colony of polyps & medusae gas float 5 9/20/2011 II. Scyphozoa (true jellyfish) scyphozoan medusa no velum thicker mesoglea aids in buoyancy III. Staurozoa stalked jellyfish (only polyp) no medusa 6 9/20/2011 IV. Cubozoa V. Anthozoa 7 9/20/2011 Hard Corals Hard Stony Corals cup coral Tubastrea sp. closed during day Montastrea cavernosa polyps open during night zoantharian 8 9/20/2011 soft octocorals 8 pinnate tentacles endoskeleton spicules with horny protein provides flexibility spicule 9 9/20/2011 Corals restricted habitats shallow depths warm temperatures Limiting factors sunlight photosynthesis water clarity Dying Coral Reefs human impact pollution development global warming Horny (gorgonian) Corals red gorgonian Melithaea sp. sea fan Subergorgia mollis red whip Ellisella sp. 10 9/20/2011 Soft coral Dendronephthya sp. 11