Phylum Cnidaria

Radially symmetricRadially symmetric DimorphicDimorphic CnidocytesCnidocytes ~10,000 species~10,000 species AquaticAquatic

Taxonomic Characteristics DiploblasticDiploblastic –Epiderm & hypoderm –Tissues

Taxonomic Characteristics DiploblasticDiploblastic Incomplete digestive tractIncomplete digestive tract –coelenteron

Taxonomic Characteristics DiploblasticDiploblastic Incomplete digestive tractIncomplete digestive tract Decentralized nervous systemDecentralized nervous system

Taxonomic Characteristics DiploblasticDiploblastic Incomplete digestive tractIncomplete digestive tract Decentralized nervous systemDecentralized nervous system CnidocytesCnidocytes

Everted nematocyst firing nematocystfiring nematocystfiring nematocystfiring nematocyst

Hydrazoan stinging and capturing prey

Cnidarian Dimorphism

Cnidarian Dimorphic Life Cycle Colonial hydrozoan

Cnidarian Taxonomy Phylum CnidariaPhylum Cnidaria –Class Hydrozoa –Class Scyphozoa –Class Cubozoa –Class Anthozoa

Phylogeny of Cnidaria Cladogram based on molecular systematic data

Class Hydrozoa Most varied and derived of the cnidarian groupsMost varied and derived of the cnidarian groups Includes freshwater species (hydra spp)Includes freshwater species (hydra spp) Colonial species commonColonial species common Most have typical dimorphic life cycleMost have typical dimorphic life cycle Examples of polyp-only forms (hydra)Examples of polyp-only forms (hydra) Examples of medusa-only formsExamples of medusa-only forms

Atypical Hydrozoans Hydra Hydra –Lacks medusa stage –Asexual - budding –Sexual - gametes

Atypical Hydrozoans Gonionemus – reduced polyp formGonionemus – reduced polyp form

Colonial Hydrozoans Colony of specialized hydranthsColony of specialized hydranths –Gonangia (gonozooids) – reproduction –Gastrozooids – feeding –Dactyolozooids – catching prey hydranths

Colonial Hydrozoans

Portuguese Man-O-War (Physalia physalis)Portuguese Man-O-War (Physalia physalis) Polyp – air bagPolyp – air bag Feeding & reproductive hydranths - tentaclesFeeding & reproductive hydranths - tentacles

Colonial Hydrozoans Fire CoralsFire Corals –NOT TRUE CORAL Hydrozoan colonyHydrozoan colony –TRUE CORAL Anthozoan colonyAnthozoan colony –Cnidocytes cause severe pain

Dimorphic Life Cycle and Reproductive Modes AsexualAsexual –Budding Medusa budsMedusa buds Polyp budsPolyp buds SexualSexual –Gonadal tissue –Gametes –Fertilization, embryogenesis –Planula larvae

Class Scyphozoa Typically thought of as jellyfishTypically thought of as jellyfish Most have typical dimorphic life cycleMost have typical dimorphic life cycle –Polyp stage is atypical –Majority of life cycle spent in medusa form

Scyphozoan Life Cycle

Aurelia aurita (Moon jelly)

CNIDARIA Class Scyphozoa Sea thimble jellyfish (Linuche unguiculata), HondurasSea thimble jellyfish (Linuche unguiculata), Honduras Tiny jellyfish (< 1 inch) that swarm in the springTiny jellyfish (< 1 inch) that swarm in the spring Adults and larvae (“sea lice”) may cause a severe skin reaction in humansAdults and larvae (“sea lice”) may cause a severe skin reaction in humans Photo Copyright © Diane R. Nelson

CNIDARIA Class Scyphozoa Upside down jellyfish (Cassiopea xamachana) from Bermuda, with zooxanthellaeUpside down jellyfish (Cassiopea xamachana) from Bermuda, with zooxanthellae This specimen is swimming up to the surface, where its reflection is visibleThis specimen is swimming up to the surface, where its reflection is visible Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Photo Copyright © Diane R. Nelson

CNIDARIA Class Scyphozoa Jellyfish (Mastigias sp., family Rhizostomeae) from Jellyfish Lake in Palau, western PacificJellyfish (Mastigias sp., family Rhizostomeae) from Jellyfish Lake in Palau, western Pacific Have lost their ability to sting and depend on zooxanthellae for nutritionHave lost their ability to sting and depend on zooxanthellae for nutrition Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display Photo Copyright © Diane R. Nelson

CNIDARIA Class Scyphozoa Lion’s Mane Jelly (Cyanea capillata)Lion’s Mane Jelly (Cyanea capillata) Bell – 6 ftBell – 6 ft Tentacles – 120 ftTentacles – 120 ft

Lion’s Mane Jelly (Cyanea capillata)

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Class Cubozoa

Phylum Cnidaria Class Cubozoa Carybdeid, Darwin, AustraliaCarybdeid, Darwin, Australia

Phylum Cnidaria Class Cubozoa Carybdea sivickisiCarybdea sivickisi South pacificSouth pacific

Phylum Cnidaria Class Cubozoa Chironex fleckeriChironex fleckeri Size of human head with tentacles (4) up to 9 ft longSize of human head with tentacles (4) up to 9 ft long ft of tentacles can deliver enough poison to kill in <5 min ft of tentacles can deliver enough poison to kill in <5 min.

Class Anthozoa Anemones & CoralsAnemones & Corals Lack medusa formLack medusa form Form colonies (especially coral)Form colonies (especially coral)

Class Anthozoa – Typical Polyp Form

CNIDARIA Class Anthozoa giant anemone or purple-tipped anemone (Condylactis gigantea) often harbors cleaning shrimp among its tentaclesgiant anemone or purple-tipped anemone (Condylactis gigantea) often harbors cleaning shrimp among its tentacles Common in Bermuda and the CaribbeanCommon in Bermuda and the Caribbean Photo Copyright © Diane R. Nelson

Anemone with Anemone Fish

Anthozoan Motility

Class Anthozoa – Hard Coral Hexacorallia – 6-fold symmetryHexacorallia – 6-fold symmetry Precipitate Ca 3 (CO 3 ) 2 from sea water to produce skeletal structures that become coral reefsPrecipitate Ca 3 (CO 3 ) 2 from sea water to produce skeletal structures that become coral reefs Contain zooxanthellaContain zooxanthella

Class Anthozoa – soft corals Octocorallia – 8-fold symmetryOctocorallia – 8-fold symmetry Form complex tube- like skeletal structuresForm complex tube- like skeletal structures Lack zooxanthellaLack zooxanthella

Phylum Cnidaria Class Anthozoa Subclass OctocoralliaSubclass Octocorallia –Soft coral

Class Anthozoa – Soft Corals

Soft Corals – Class Anthozoa

Reefs Shallow tropical watersShallow tropical waters Hermatypic corals (Class Anthozoa, subclass hexacorallia, order scleractinia)Hermatypic corals (Class Anthozoa, subclass hexacorallia, order scleractinia) Contain symbiotic dinoflagellatesContain symbiotic dinoflagellates Precipitate CaCO 3 to form “exoskeleton”Precipitate CaCO 3 to form “exoskeleton”

Zooanthella Green algaeGreen algae

Atoll

Phylum Ctenophora Comb-jelliesComb-jellies –Rows of cells with fused cilia – comb-plates <100 species<100 species Lack cnidocytesLack cnidocytes Complete digestive tractComplete digestive tract

Ctenophore Morphology

Ctenophore Body Forms Biradial symmetryBiradial symmetry –Two tentacle clusters –Even # comb rows\ Some are bilateralSome are bilateral

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