13-1 chapter 13 radiate animals phylum cnidaria radiate animals phylum cnidaria

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CHAPTER 13CHAPTER 13CHAPTER 13CHAPTER 13

Radiate AnimalsRadiate AnimalsPhylum CnidariaPhylum CnidariaRadiate AnimalsRadiate AnimalsPhylum CnidariaPhylum Cnidaria

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Phylum Cnidaria

Fossil specimensFossil specimens dated to over dated to over 700 million 700 million years agoyears ago

General Characteristics Soft bodied Carnivorous Stinging tentacles Examples: Jellyfish, sea anemones


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Phylum CnidariaPhylum Cnidaria

Classes of CnidariaClasses of Cnidaria Hydrozoa (Portuguese Man-of-War, Hydra)Hydrozoa (Portuguese Man-of-War, Hydra) Scyphozoa (True Jellyfish - Aurelia)Scyphozoa (True Jellyfish - Aurelia) Anthozoa (Sea Anenome, Corals)Anthozoa (Sea Anenome, Corals)


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Characteristics of Phylum Cnidaria Characteristics of Phylum Cnidaria All areAll are aquatic aquatic and mostly marine and mostly marine SymmetrySymmetry

RadialRadial Two body typesTwo body types

Free-swimming medusa Free-swimming medusa Sessile polypsSessile polyps

Acoelomates - No coelomAcoelomates - No coelom Diploblastic Diploblastic Blind (Incomplete) GutBlind (Incomplete) Gut


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Tentacles Tentacles usually encircle mouth or oral usually encircle mouth or oral regionregion Equipped with specialized cells: Equipped with specialized cells: cnidocytes cnidocytes

CnidocytesCnidocytes: stinging cells located on their tentacles: stinging cells located on their tentacles NematocystNematocyst: : stinging organelle, poison-filled structure that stinging organelle, poison-filled structure that

contains a tightly coiled dart.contains a tightly coiled dart.

Muscular contractionsMuscular contractions via epitheliomuscular via epitheliomuscular cellscells layers of longitudinal and circular fibers layers of longitudinal and circular fibers

Sense organsSense organs for balance ( for balance (statocystsstatocysts) and ) and photosensitivity (photosensitivity (ocelliocelli))


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Nerve net Nerve net Simple nervous system, no brainSimple nervous system, no brain Interconnected NeuronsInterconnected Neurons Used to sense physical contactUsed to sense physical contact

Asexual reproductionAsexual reproduction Budding in polypsBudding in polyps

Sexual reproduction Sexual reproduction By gametes in all medusae and some polypsBy gametes in all medusae and some polyps Monoecious or DioeciousMonoecious or Dioecious

No No excretory or respiratory systemexcretory or respiratory system


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A. Hermit crab uses cnidrian as protectionB. Showing growth on host shell


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Form and Function Form and Function Cnidaria have two basic body plans: Cnidaria have two basic body plans:

polyp and medusapolyp and medusa Polyp Polyp

Internal Body CavityInternal Body Cavity Adaptation to a sedentary lifeAdaptation to a sedentary life Tubular body with the mouth directed upward Tubular body with the mouth directed upward

and surrounded by tentaclesand surrounded by tentacles Mouth leads into a blind-gut cavityMouth leads into a blind-gut cavity Reproduce asexually by budding, fission, or Reproduce asexually by budding, fission, or

pedal lacerationpedal laceration


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Phylum Cnidaria - MedusaPhylum Cnidaria - Medusa MedusaMedusa

Bell or umbrella-shapedBell or umbrella-shaped Usually free-swimmingUsually free-swimming Mouth directed downward Mouth directed downward Tentacles may extend down from rim of Tentacles may extend down from rim of

umbrellaumbrella Medusae equipped with statocysts (direction) Medusae equipped with statocysts (direction)

and ocelli (light/vision)and ocelli (light/vision)


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Body WallBody Wall Cnidarian bodyCnidarian body

Outer Outer epidermisepidermis Inner Inner gastrodermisgastrodermis (gastrovascular cavity = gut) (gastrovascular cavity = gut) Layers separated by Layers separated by mesogleamesoglea Mesoglea Mesoglea

Gelatinous (at least 95% water) - jellylikeGelatinous (at least 95% water) - jellylike Continuous, extending through body and Continuous, extending through body and

tentaclestentacles Supports bodySupports body Thickness variesThickness varies


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Life CyclesLife Cycles Polyps and medusae play different roles in the Polyps and medusae play different roles in the

cnidarian life cyclecnidarian life cycle Typically, zygote develops into a motile Typically, zygote develops into a motile

planula larvaplanula larva Planula settles, and metamorphoses into a Planula settles, and metamorphoses into a

polyppolyp Produce other polyps asexuallyProduce other polyps asexually Polyps eventually produce a free-swimming Polyps eventually produce a free-swimming

medusa by asexual reproductionmedusa by asexual reproduction BuddingBudding



Hydrozoan Life Cycle


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Epitheliomuscular and Nerve Cells


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CnidocytesCnidocytes Many cnidarians are Many cnidarians are effective predatorseffective predators Possibly due to presence of a unique cell Possibly due to presence of a unique cell

type, type, the cnidocyte (discharged = cnidae)the cnidocyte (discharged = cnidae) Nematocyst- Nematocyst- inside cnidocytes, poison-filled inside cnidocytes, poison-filled

stinging structurestinging structure


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Nematocyts Nematocyts Tiny capsules containing a coiled filamentTiny capsules containing a coiled filament End of capsule is coveredEnd of capsule is covered Filament may have tiny barbs or spinesFilament may have tiny barbs or spines Tactile stimulation of Tactile stimulation of cnidocilcnidocil, causes nematocyst , causes nematocyst

to dischargeto discharge After discharge, cnidocyte is absorbed and After discharge, cnidocyte is absorbed and

another developsanother develops


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Mechanism of Nematocyst Discharge Mechanism of Nematocyst Discharge When stimulated, water rushes into the capsuleWhen stimulated, water rushes into the capsule The operculum (cap) opens and rapidly launches the The operculum (cap) opens and rapidly launches the

filamentfilament Barbs Barbs inject poisoninject poison into prey into prey Only a Only a few jellyfish - including the Portuguese man-of-few jellyfish - including the Portuguese man-of-

warwar can seriously harm humans can seriously harm humans Topical Solutions if stung: Topical Solutions if stung:

acidic (vinegar) acidic (vinegar) Urine - only if urine is acidic?? Most urine is sterile.Urine - only if urine is acidic?? Most urine is sterile. Apply heat or ice for pain (also denatures toxins)Apply heat or ice for pain (also denatures toxins) Salt water should be applied to remove any excess Salt water should be applied to remove any excess

toxins.toxins.


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Discharged cnidae

recoiled


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Feeding and DigestionFeeding and Digestion PolypsPolyps

Typically Typically carnivorouscarnivorous Catch prey with tentacles and pass them to the Catch prey with tentacles and pass them to the

gastrovascular cavitygastrovascular cavity Gland cells discharge enzymes to begin Gland cells discharge enzymes to begin

extracellular digestionextracellular digestion Intracellular digestionIntracellular digestion continues in the continues in the

gastrodermisgastrodermis


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Nerve NetNerve Net Allow cnidarians to detect stimuliAllow cnidarians to detect stimuli Unlike higher animals, Unlike higher animals,

Nerve nets have neurotransmitters on both sides of the Nerve nets have neurotransmitters on both sides of the synapses synapses

Allowing transmission in either directionAllowing transmission in either direction No myelin sheath on axons - like humansNo myelin sheath on axons - like humans

Nervous system also has Statocysts and OcelliNervous system also has Statocysts and Ocelli


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Class Hydrozoa: AnimalsClass Hydrozoa: Animals HydraHydra

Found in Found in fresh waterfresh water Worldwide distributionWorldwide distribution (16 species in North America) (16 species in North America) Body is a cylindrical tubeBody is a cylindrical tube Ring of 6–10 hollowRing of 6–10 hollow tentacles tentacles encircles mouth encircles mouth

Portuguese Man-of-WarPortuguese Man-of-War Floats on surface (air bladder)Floats on surface (air bladder) Tentacles reach up to 10 metersTentacles reach up to 10 meters Contains polyp colonies and medusaContains polyp colonies and medusa


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Class HydrozoaClass Hydrozoa Most marine and colonial with both polyp and Most marine and colonial with both polyp and

medusa forms (polyp form dominates)medusa forms (polyp form dominates) Hydra, hydrozoan, hydroidHydra, hydrozoan, hydroid Medusa have Medusa have velumvelum

Layer inside bell to close off outsideLayer inside bell to close off outside ColonialColonial Obelia Obelia

Typical hydroid has a Typical hydroid has a base, a stalkbase, a stalk, and one or , and one or more individual polyp animalsmore individual polyp animals

Feeding polypsFeeding polyps with tentacles around mouth= with tentacles around mouth= hydranthshydranths

In Obelia, the medusae buds are formed by a In Obelia, the medusae buds are formed by a reproductive polypreproductive polyp called a called a gonangiumgonangium


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Obelia Life Cycle


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Hydroids


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Bell medusa(Hydroid)


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MedusaD. Developing Polyp from Planula: Frustule = bud


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Freshwater Hydrozoan


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Hydra catching a water flea


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Hydras reproduce Hydras reproduce sexually and asexuallysexually and asexually Asexual reproduction Asexual reproduction

BuddingBudding Most Most hydrahydra are are dioeciousdioecious

Temporary gonadsTemporary gonads appear in autumn, appear in autumn, stimulated by lower temperatures stimulated by lower temperatures

Eggs and sperm shed externally, Eggs and sperm shed externally, external fertilizationexternal fertilization

Cyst Cyst forms around embryoforms around embryo Encysted form endures the winter, Encysted form endures the winter,

then young hydras hatch in the springthen young hydras hatch in the spring


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Hydra w/ developing bud and ovary/egg


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Portuguese man-of-war ColonySecrete powerful neurotoxin - Class Hydrozoa


Differences between Hydrozoa and Scyphozoa

Hydrozoa Have Velum - protecting

muscle on inward side of bell

Colonial Stages Mostly Polyp life form Medusa, if present, are

usually small Small amounts of mesoglea

and no cells 4 tentacles

Scyphozoa Large Medusa forms Polyps are sedentary No velum Cells present in mesoglea More complex More tentacles Large amount of mesoglea


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Class Hydrozoa:Hydrocorals - form calcareous skeletons to resemble true coral.

B. “Fire Coral” - Nematocysts cause burning sensation to human skin


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Class ScyphozoaClass Scyphozoa Most of the Most of the larger jellyfisheslarger jellyfishes belong to this belong to this

classclass Nearly all Nearly all float in open seafloat in open sea Bells vary in shape and sizeBells vary in shape and size

Composed mostly of Composed mostly of mesoglea mesoglea Lack subumbrellar membrane - velumLack subumbrellar membrane - velum found found

in hydrozoan medusaein hydrozoan medusae


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Class Scyphozoa

Giant jellyfish


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Moon Jellyfish(Aurelia)


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Phylum Cnidaria - ScyphozoaPhylum Cnidaria - Scyphozoa

Reproduction methodsReproduction methods Asexual - Similar to other cnidarians. BuddingAsexual - Similar to other cnidarians. Budding But also use But also use StrobilationStrobilation - asexual budding of - asexual budding of

saucerlike buds that develop into medusa.saucerlike buds that develop into medusa.


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Life Cycle of Aurelia, marine scyphozoan


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Class AnthozoaClass Anthozoa Lack a medusa stageLack a medusa stage All marine,All marine, in both deep and shallow water, in both deep and shallow water,

and vary in sizeand vary in size Examples: sea anemones, sea coralsExamples: sea anemones, sea corals


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Sea Anemones


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Structure of Sea Anemone


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Phylum Cnidaria - AnthozoaPhylum Cnidaria - Anthozoa

No special organs for respiration or excretionNo special organs for respiration or excretion

Sea AnemonesSea Anemones Polyps larger and heavier than hydrozoan Polyps larger and heavier than hydrozoan

polypspolyps Attach to shells, rocks, timber, etc. by pedal Attach to shells, rocks, timber, etc. by pedal

discsdiscs


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Some burrow in mud or sandSome burrow in mud or sand Crown of tentacles surrounds the flat oral discCrown of tentacles surrounds the flat oral disc Slit-shaped mouth leads into a pharynxSlit-shaped mouth leads into a pharynx Transports oxygen, removes wastes, and Transports oxygen, removes wastes, and

maintains fluid pressure for a hydrostatic maintains fluid pressure for a hydrostatic skeletonskeleton

When in danger,When in danger, water rapidly expelled through pores water rapidly expelled through pores as the anemone contracts to a small sizeas the anemone contracts to a small size


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Sea Anemone being attacked by a Sea Star

Can Sea Anemones run?


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Tube Anemone


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Reproduction of Sea AnemonesReproduction of Sea Anemones Some Some dioecious,dioecious, some some monoeciousmonoecious Monoecious species - Monoecious species - produce sperm first and produce sperm first and

eggs latereggs later Fertilization is external or in gastrovascular Fertilization is external or in gastrovascular

cavitycavity Zygote becomes a Zygote becomes a ciliated larvaciliated larva Pedal laceration, small pieces of pedal disc Pedal laceration, small pieces of pedal disc

break off and regenerate a small anemonebreak off and regenerate a small anemone Longitudinal and transverse fission, and Longitudinal and transverse fission, and

budding occur budding occur


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Closed during day, open to feed at night


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Polyp ofCoral


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Boulder Star Coral


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A Thorny Coral


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A soft coral on Pacific Coral Reef


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Sea Fan Red Whip CoralHorny Coral


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Coral ReefsCoral Reefs Great diversityGreat diversity of organisms (under rainforest) of organisms (under rainforest) Plants and animals are limited to top layer Plants and animals are limited to top layer

Above the calcium carbonate depositsAbove the calcium carbonate deposits Hermatypic (reef forming) corals and coralline algae Hermatypic (reef forming) corals and coralline algae

(precipitate calcium carbonate)(precipitate calcium carbonate) form most coral reefs form most coral reefs Require warmth, light, and salinity of undiluted Require warmth, light, and salinity of undiluted

sea water (contains calcium)sea water (contains calcium) Limited to shallow waters between 30 degrees Limited to shallow waters between 30 degrees

north and 30 degrees south latitudenorth and 30 degrees south latitude Photosynthetic zooxanthellae live in their tissuesPhotosynthetic zooxanthellae live in their tissues Provide food for corals and recycle phosphorus Provide food for corals and recycle phosphorus

and nitrogenous wastesand nitrogenous wastes


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Barrier Reef


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Phylum Cnidaria - Human ImpactPhylum Cnidaria - Human Impact

Nutrients from fertilizer and sewage threaten coral Nutrients from fertilizer and sewage threaten coral reefs with excessive algal growth - or by killing reefs with excessive algal growth - or by killing zooxanthellae, which leads to coral bleaching.zooxanthellae, which leads to coral bleaching.

Persian Gulf reefs have withstood surprising Persian Gulf reefs have withstood surprising amounts of oil pollutionamounts of oil pollution

Coral reefs in many areas are threatened by factors Coral reefs in many areas are threatened by factors mostly of human originmostly of human origin

Higher atmospheric concentrations of carbon Higher atmospheric concentrations of carbon dioxide (from burning hydrocarbon fuels) tends to dioxide (from burning hydrocarbon fuels) tends to acidify ocean water, which makes precipitation of acidify ocean water, which makes precipitation of CaCOCaCO33 by corals more difficult metabolically by corals more difficult metabolically

13-1 chapter 13 radiate animals phylum cnidaria radiate animals phylum cnidaria

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