The Characteristics of Phylum Cnidaria

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The Characteristics of Phylum Cnidaria
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Phylum Cnidaria
Class Anthozoa
Class Hydrozoa
Class Scyphozoa
Class Cubozoa
Corals Anemones
Hydra Portuguese Man-Of-War Stinging Limu Fire
Coral
True jellyfish
Box jellies Sea wasps
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Characteristics of Phylum Cnidaria

• radial symmetry
• blind sac gut ( coelenteron or gastrovascular
  cavity)
• diploblastic with mesoglea
• polyp and medusa body forms
• nematocysts ( specialized stinging capsules)
• nerve net
• lack excretory, circulatory respiratory systems
• complex life cycle
• many colonial forms exhibiting polymorphism

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Radial Symmetry
oral
Polyp
aboral
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Radial Symmetry
JellyfishPhylum Cnidaria
Medusa
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Blind Sac Gut
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Diploblastic- two germ layers
Phylum Cnidaria
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Nematocysts
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Nematocyst Picture
Nematocyst
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More Nematocysts
http//www.youtube.com/watch?NR1v-Tp38DUjUnMfe
atureendscreen
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Nerve Net
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Diffusion Across the Body Wall
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Sea Anemones
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Circulation in a Moon Jellyfish
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The Cnidarian Life Cycle
The Cnidarian Life Cycle
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Coloniality
CoralPhylum Cnidaria
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General Characteristics of Cnidaria

• Stinging cells
• Two stages in life cycle (polyp medusa)
• Blind sack gut
• Radial symmetry
• Diploblastic
• Hydrostatic skeleton
• Nerve net
• Many colonial, some solitary forms

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Class Hydrozoa
(Gr. hydra, water serpent)

• polyps and medusa stage, although polyp stage is
  dominant.
• gut cavity of polyp is simple, lacking a pharynx
  and not divided by mesenteries.
• tetramerous (four-part) radial symmetry.
• gonads are ectodermal (found in the epidermis).
• medusa stage may possess specialized balance
  organs called statocysts and photosensitive
  organs called ocelli.
• solitary or colonials some colonial forms highly
  polymorphic.
• includes hydroids (stinging limu), fire coral,
  pink coral, and siphonophores.

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The Cnidarian Life Cycle
The Hydrozoan Life Cycle
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Hydrozoan Colony
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Hydrozoan ColoniesStinging Limu
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Hydrozoan Medusa
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Hydrozoan Medusa
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Hydrocorals
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Fire Coral
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By-the-Wind-SailorA Floating Colony of Polyps
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Coloniality and Polymorphism
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Poly,orphism in the Portuguese Man- of-War
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Class Scyphozoa
(Gr. skyphos, cup)

• life cycle with both polyps and medusae, but
  medusae dominate with polyp stage reduced or
  absent.
• polyp stage (scyphistoma) goes through
  strobilization to produce young medusa.
• bell margin lacks a velum.
• tetramerous ( four-part) radial symmetry.
• gut divided into a complex system of radial
  canals.
• some with a simple single mouth, but many with
  thousands of microscopic mouths at the ends of
  oral arms.
• gonads endodermal (found in the gastrodermis).
• specialized sense organs called rhopalia with
  ocelli statocysts .
• includes some 200 marine species.
• "true" sea jellies.

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Moon Jelly Anatomy
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Scyphozoan Life Cycle
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Sea Jellies
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Class Cubozoa
(Gr. kybos, a cube)

• polyps and medusae stages, but medusae dominate
  with polyp stage reduced.
• polyp stage develops directly into medusa.
• bell margin with a velarium.
• tetramerous ( four-part) radial symmetry bell
  cube-shaped with tentacles arising from each
  corner.
• gonads endodermal (found in the gastrodermis).
• specialized sense organs called rhopalia with
  ocelli statocysts .
• includes some 15 marine species.
• includes box jellies and sea wasps.

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Seawasp
Box Jellies
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Box Jelly Anatomy
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Class Anthozoa
(Gr. anthos, flower)

• lack medusa stage entirely (polyp forms only)
• mouth with a tubular pharynx that projects inward
  into the gut
• large gut cavity divided by mesenteries that
  radiate inwards from the body wall
• gonads endodermal, borne on the mesenteries
• hexamerous (6-part) or octamerous (8-part) radial
  symmetry or biradial (modified radial symmetry
  that limits the number of planes that can divide
  the body into equal halves
• includes sea anemones, true stony corals, sea
  fans, sea pens, organ pipe coral, precious black
  coral, zoanthids

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Subclass Zoantharia Order Actinaria Sea Anemones
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Sea Anemone Anatomy
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Subclass Hexacorallia Order Zoanthidae

• No hard skeleton
• May be tough and leathery
• Shallow water forms
• Encrusting forms
• Some with zooxanthellae
• Polyp stage only

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Subclass Hexacorallia Order Antipatheria Black
Coral Wire Coral
Black coral
Wire coral
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Subclass Hexacorallia Order Scleractinia True
Stony Corals
Hermatypic- reef building, zooxanthellae

• Common species
• Acroporidae- table
• Acroporidea- rice
• Agariciidae- flat lobe, corrugated
• Faviidae- crust, ocellated
• Fungiidae- humpback, mushroom
• Pocilloporidae- lace, antler, cauliflower
• Poritidae- finger, lobe, plate

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True Stony Corals
lobe
finger
mushroom
Porites rus
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Subclass Alyconaria Octocorals

• 8 branched tentacles surrounding the mouth
• Both hard and soft forms exist
• Ahermatypic- non reef building, no photosynthesis
• Five Orders found in Hawaii
• Stolonifera
• Pennatulacea (sea pens)
• Alcyonacea (soft corals)
• Telestacae (snowflake corals)
• Gorgonacea (sea fans)

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Octocorals
Sea pen
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Organ pipe coral