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Phylum

Cnidaria

Danilo V. Rogayan Jr.Faculty, College of Education, Arts and Sciences

Ramon Magsaysay Technological University

PHYLUM CNIDARIAJellyfish, sea anemones, corals

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Phylum Cnidaria

• Some unique characteristics

• Nematocysts

• Alternation of generations

• (polyp and medusa body forms)

• Planula larva

• Mesoglea

Sea anemones

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Members of this phylum have tentacleswith stinging cells.

Cnidaria Systems

• Integumentary• One cell layer (epidermis)

• Skeletal• Hydrostatic or some with endoskeletons and/or

exoskeleton of calcium carbonate (Anthozoa)

• Muscle• None; epith-muscle cells (fibers from cells into

mesoglea) Anthozoa may have muscles

• Digestive• Incomplete

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Cnidaria Systems

• Excretory• Isotonic in marine; some freshwater forms use

contractile vacuoles)

• Respiratory• No system , use cellular diffusion

• Circulatory• No system, use cellular diffusion and mesoglea

• Nervous• Nerve net (ring around the bell of medusa)

Cnidaria Systems

• Endocrine

• Have hormones, secreted by nervous system

• Reproductive

• Alternation of generations, vary as to dominant

stage

• Medusa is the sexual body plan

• Polyp is the asexual body plan

• Planula larva

• Dioecious or monoecious

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Cnidarians can have one of two body shapes: an umbrella-shaped medusa form, like the jellyfish on the left, or a vase-shaped polyp form, like the sea anemone on the right.

Freshwater Hydra Comb Jellies

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Coral reefs contain many members of Phylum Cnidaria.

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Cnidaria Taxonomy

• Class Hydrozoa(hi-dro-zo-ah)

• Hydra,

• Obelia,

• Gonionemus,

• Physalia

• Class Scyphozoa(sky-fo-zo-ah)

• Aurelia

• Class Anthozoa(an-tho-zo-ah)

• Metridium

• Tubipora

• Gorgonia

• Other anthozoan coral

• Class Cubozoa(ku-bo-zo-ah)

• No specimens

Class Hydrozoa

• Alternation of generation with polyp as the dominant body plan

• Incomplete digestive with an unbranched gut.

• Mesoglea thin

• Medusa with a velum

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Class HydrozoaGenus— Hydra

CS through hydra

Class HydrozoaGenus— Obelia

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Class HydrozoaGenus— Gonionemus

Class HydrozoaGenus— Physalia

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Class Scyphozoa

• Alternation of generation with medusa the

dominant body plan

• Incomplete digestive with four branches

• Mesoglea thick with some cells

• Medusa without velum

Class ScyphozoaGenus— Aurelia

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Class Anthozoa

• No alternation of generation - polyps only

• Incomplete digestive with 6 to 8 branches

(septia)

• Nematocyst in the gut (acontia)

• Mesoglea thick and with muscle tissue

• Coral Reefs

Class AnthozoaGenus — Metridium

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Class AnthozoaGenus — Tubipora

Class AnthozoaGenus — Gorgonia

Sea fan

String coral

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Other Anthozoan Coral

AstrangiaFungia

Sea pansyLettuce coral

Brain coral

Coral Reefs

• Fringing reef• Close to land mass none or a narrow lagoon

between land and shore.

• Barrier reef• Has a wide and deep lagoon between reef and

shore line.

• Atolls• Reefs that encircle a lagoon, but there is no island

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