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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
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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
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Five Classes
I. Hydrozoa
Ectopleura
Hydra: freshwater species
no medusa stage
budding
Corymorpha
Hydroids
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Polymorphism
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Craspedacusta
freshwater hydrozoan
Portuguese Man of War Physalia physalis
colony of polyps & medusae
gas float
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II. Scyphozoa (true jellyfish)
scyphozoan medusa
no velum
thicker mesoglea aids in buoyancy
III. Staurozoa
stalked jellyfish (only polyp) no medusa
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IV. Cubozoa
V. Anthozoa
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Hard Corals
Hard Stony Corals
cup coral Tubastrea sp.
closed during day
Montastrea cavernosa polyps
open during night
zoantharian
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soft octocorals
8 pinnate tentacles
endoskeleton
spicules with horny protein
provides flexibility
spicule
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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.
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Soft coral Dendronephthya sp.
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