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Phylum Cnidaria

Created for use with BIO 2215

Oklahoma City Community College

Dennis Anderson

Moore High SchoolZoology

Adapted by: Tamara Lookabaugh

Background Information

• 9000 Species

• 700 Million Years Old

• Symbiosis with Algae, Coral use them to gain nutrition and build reefs

• Cnidocytes containing Nematocysts to capture prey

• 4 Classes – Hydrozoa, Scyphozoa, Anthozoa, Cubozoa

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Phylum Cnidaria • Marine, Few Freshwater• Radial symmetry with oral

and aboral ends• Two body forms

– Polyp vs. Medusa

• One opening into and out of gastrovascular cavity.

• Cnidocytes on tentacles, epidermis and internal

• Ocelli and Statocysts• Sexual and Asexual• Nerve net• Diffusion to breathe and

release waste• Carnivores, filter feeders

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Radial symmetryRadial symmetry

Hydra Polyp looking over the top

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Mouth and Tentacles

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Fig. 13.2

Body Forms

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Polyp form•Body is tube with tentacles•Aboral end attached by pedal disc•Anthozoans only have this form

Medusa form•Bell or umbrella shaped•Tetramerous-arranged in fours•Some species have both body forms, medusa is considered the adult, polyp is juvenile•Scyphozoans are mostly medusa form

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Cnidocyte Structure and Nematocyst Discharge

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Stinging StructureCnidocytes produce and hold the stinging structure called NEMATOCYSTS.

Cnidocil – hair-like trigger

Operculum – door or flap to hold in harpoon

Nematocysts – coiled up harpoon like structure (some have toxin and are barbs)

Discharge is caused by:

High Osmotic pressure, brushing against

Cnidocil by prey 40,000x acceleration of gravity, 5 g’s 9

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Generalized Cnidarian Life Cycle

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Nervous System• Nerve cells, arranged in a nerve net.

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AnthozoaScyphozoa Cubozoa

Hydrozoa

Radial symmetry, cnidocytes, planula larva

Septa divide gastrovascular cavity

Medusa cuboidal

Polyp stage reducedLoss of medusa

Cladogram of Cnidaria

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Class Hydrozoa• Means “Water Serpent or Animal”• Cnidocytes present only on

epidermis.• Most have Polyp and Medusa

stage.• Most are marine and colonial.• Asexual reproduction by budding.• Sexual reproduction via gametes

produced by epidermis & released into water.

• Monoecious

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Class Hydrozoa

Example Organisms:

•Hydra (movement) - Freshwater

Pedal laceration, can tumble, climb, walk

•Obelia form and life cycle

•Gonionemus (different views)

•Physalia (video national geographic)

(Portuguese Man O War – open ocean)

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Class HydrozoaHydra

SpermariesSpermariesSpermariesSpermaries

OvariesOvariesOvariesOvaries

EncapsulatedEncapsulatedembryoembryo

EncapsulatedEncapsulatedembryoembryo

Sexual cycleSexual cycleSexual cycleSexual cycle Asexual cycleAsexual cycleAsexual cycleAsexual cycle

BuddingBuddingBuddingBudding

Sperm and Egg unite from sperm and egg factories

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Obelia

Hydranth with Gastrozooid “Feeding Polyp”

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Obelia

Medusae

GonangiumMedusa bud

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Obelia

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Class HydrozoaGonionemus

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Class HydrozoaGonionemus

Velum

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Class HydrozoaPhysalia “Portuguese man-o-war”

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Class Scyphozoa• Means “Cup Animal”• Largest Jellyfish• Tentacles can reach 70

meters – Open Ocean• Umbrellas have

indentations with rhopalium & lappet containing sense organs – ocelli & statocysts

• Manubrium(mouth) surrounded by 4 oral arms

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Class ScyphozoaAurelia- “Moon Jelly”

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Aurelia Life History

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Strobilation

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Fig. 13.18Scyphozoa are

Dioecious

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Planula LarvaPlanula Larva

Ciliated larva than can swim to a new location

Larva of Scyphozoa areCreated by sperm from oneMale ephyrae that releasesSperm on female ephyraeMedusa arm and meets anEgg to form a zygote whichBecome a planula.

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Aurelia

Mouth

Oral arm

Gastric pouch

Tentacles

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Class Anthozoa• Means “flower animal”• Medusa stage absent• Solitary or colonial• Some produce protective

skeletons• Tentacles around mouth working

with siphinoglyph creating water currents

• Cnidocytes internal ejected out• Anemones glide, pedal laceration• All Marine• Protandrous, mono and dioecious

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Class AnthozoaSea Anemone

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Class AnthozoaMetridium

Class AnthozoaMetridium

MouthMouthMouthMouth

TentaclesTentaclesTentaclesTentacles

PharynxPharynxPharynxPharynx

SeptumSeptumSeptumSeptum

Gastrovascular cavityGastrovascular cavityGastrovascular cavityGastrovascular cavity

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Symbiosis

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Class AnthozoaCorals

• Protective skeleton of calcium carbonate

• Polyp retracts when not feeding

• Hexacorallia• Found in warm

tropical seas

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Class Anthozoa - Zooxanthellae

• Photosynthetic dinoflagellates (brown)

• Live in corals• Provide nutrients for

coral by photosynthesis

• Mutualism

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Class Anthozoa - CoralsColony of interconnected polyps

Class Anthozoa - CoralsColony of interconnected polyps

• Important recyclers of phosphorus and waste materials• Greatest diversity of all the marine life in the oceans

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Class AnthozoaMeandrina

Brain Coral (coral spawning link)

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Class AnthozoaGorgonia

Sea Fan

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Class AnthozoaTubipora

Pipe Organ Coral

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Class AnthozoaActinodiscusMushroom Coral

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Class AnthozoaAcropora

Staghorn Coral

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Coral Reefs• Formed over thousands of years

from successive layers of coral skeleton deposits (calcium carbonate forms underwater mountains of coral animal skeletons)

• The underwater equivalent of the amazon jungle- very high species diversity and biomass

• Reefs contain sponges, colonial hydrozoans, anemones, many varieties of coral, fish, many types of worms we’ve not discussed, not to mention bryozoans, ctenophores, protists, bacteria, etc etc..

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Coral Reef Ecosystem

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Photo © McGraw-Hill Higher Education, Barry Barker, Photographer

Types of Reefs

• Fringing Reef – Near land with no lagoon

• Barrier Reef – Parallel to land with wide and deep lagoon

• Atoll – Encircles a lagoon with a steep bank

• Bank Reef – Greater distance from land

Largest Reef in the world is the Great Barrier Reef 1200 miles around the coast of Australia.

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Fringing Reef

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Barrier Reef

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Atoll

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Bank Reef

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Class Cubozoa- all are dangerous

• Means “cube animal” Box jellies

• Tentacles arise at four corners from blade-like pendalium.

• All marine

• Strong swimmers which prey primarily on fish voracious eaters

• Stings of some may be fatal within minutes to humans.

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Class Cubozoa

GonadGonadGonadGonad

TentacleTentacleTentacleTentaclePedaliumPedaliumPedaliumPedalium

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Class CubozoaChironex fleckeri Sea Wasp

Also known as “THE HAND OF DEATH”

Chironex and Irukandji

• Video on Chironex

fleckeri

Video on Irukandji

stings

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The End