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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
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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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
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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