1 cnidarians & ctenophorans 1copyright cmassengale

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Cnidarians & Ctenophorans

1copyright cmassengale

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CNIDARIANSCNIDARIANScopyright cmassengale

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Phylum CnidariaPhylum Cnidaria•About 9000 species•Most are marine

(jellyfish, coral, sea anemones, Portuguese man-of war)

•Hydras are found in freshwater

•All have arm-like tentacles


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Cnidarian Cnidarian CharacteristicsCharacteristics

•Radial symmetry•Hollow gut -

Gastrovascular cavity has single opening (serves as both mouth and anus)

•Two tissue layers (diploblastic)

•Outer epidermis and inner gastrodermis


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•Either tubular or bell shaped•Tentacles surround mouth•Only animal with cnidocytes (stinging cells) found in the tentacles•Nematocyst – coiled, harpoon-like stinger inside cnidocyte that shoots out


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•Cnidocytes contain poison to paralyze prey•Tentacles bring food into mouth•Inner gastrodermis secretes digestive juices into gastrovascular cavity which digests food and circulates nutrients


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Extracellular DigestionExtracellular Digestion

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Food digeste

d outside of cells

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CnidocyteCnidocyte

Coiled nematocyst


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NematocystNematocyst

Barbed, threade

d stinger

capsule’s lid

trigger

nematocyst 9copyright cmassengale

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Cnidarian SystemsCnidarian Systems

•Have a simple nerve net & sensory receptors•Muscles help in directional movement & capturing prey


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mesoglea-filled bell

tentacles

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Jellylike mesoglea

between two cell layers supports cnidarian


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Two Main Body Plans of Two Main Body Plans of CnidariansCnidarians

epidermis

mesoglea

gastrodermis

Medusa

Polyp

UPRIGHT TENTACLESTENTACLES HANG DOWN

mouth

Mesoglea THICK Mesoglea THINcopyright cmassengale

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Cnidarian DiversityCnidarian Diversity

• Scyphozoans:

Jellyfish

• Anthozoans:

Sea anemones

Corals

• Hydrozoans:

Hydra

• Cubozoa

Box Jellies15copyright cmassengale

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Cnidarian DiversityCnidarian Diversity

16Sea Anemone Coral polyps

JellyfishCoral polyps


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Scyphozoanscopyright cmassengale

Scyphozoan Scyphozoan CharacteristicsCharacteristics

Jellyfish

• Medusa is dominant body form

• Go through small polyp stage during life cycle

•Stinging tentacles

•May live close to shore or the open ocean

Parts of a JellyfishParts of a Jellyfish

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Some Jellyfish Some Jellyfish Show Show

LuminescenceLuminescence

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Jellyfish Jellyfish Life CycleLife Cycle

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AnthozoaAnthozoansns


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Anthozoan Characteristics

Sea AnemonesBrightly colored &

Resemble flowers

Solitary polyps

Feed on invertebrates & fish

CoralsMost are colonial

Build limestone case

Live as polyps in their case


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Sea Sea Anemones Anemones

& Coral& Coral•Exist only

as Polyps

•Clownfish live in anemone tentacles

•Corals build a limestone case which build up & form reefs

ANEMONE

CORALcopyright cmassengale

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Distribution of Coral Distribution of Coral ReefsReefs


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Hydrozoans


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HydrozoansHydrozoansHydra

•Exist as polyps in their dominant form.

•Reproduce by budding

•Freshwater only

•Form resistant zygotes when environment is bad

•Move by somersaulting with tentacles


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Hydra


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Hydra Feeding


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Food in Gastrovascula

r Cavity


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•Colonial Hydrozoan (not a single organism

•Tentacles sting prey such as fish & humans

•Polyps in colony feed

•Has gas-filled air float

Portuguese Portuguese man-of-warman-of-war


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Blue Dragon Mollusk – Man of War Predator!!

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Hydrozoan Life CycleHydrozoan Life Cycle

Most hydrozoans alternate polyp and medusa forms, as in the life cycle of Obelia


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ObeliaObelia Life Cycle (Hydrozoan) Life Cycle (Hydrozoan)Larva called a Larva called a planulaplanula

reproductivepolyp

female medusa male medusa

sperm

zygote

ovum

planulaplanulapolyp formin

g

feeding

polyp

Fig. 25-15a, p.411copyright cmassengale

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CubozoansCubozoans

Box JellyFish


Chironex fleckeri


Australian shores

100 human deaths in the last 100 years

Venom can kill in 3 minutes

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CTENOPHORACTENOPHORANSNS


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Ctenophoran Ctenophoran CharacteristicsCharacteristics

•Called comb jellies

•All marine

•Approximately 100 species

•May be spherical, ovoid, or elongate in appearance

•Bioluminescentcopyright cmassengale

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Ctenophoran Ctenophoran CharacteristicsCharacteristics

•Radial symmetry

•Have eight plates of fused cilia that resemble combs

•Move by beating cilia

•Most of the body is jelly-like mesoglea

•Body & tentacles covered with sticky mucus to catch prey


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Comb Comb Jelly Jelly

AnatomyAnatomy


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CtenophorCtenophore:e:

Comb JellyComb Jelly45

Beating Cilia


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CtenophoreCtenophore

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1 cnidarians & ctenophorans 1copyright cmassengale

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