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Phylum Platyhelminthes

Oklahoma City Community College

Created by Dennis Anderson

ZoologyMoore High School

modified by Tamara Lookabaugh

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Phylum PlatyhelminthesGeneral Characteristics1. Flat worms

2. Triploblastic

3. Acoelomate

4. Bilateral symmetry

5. Reproduction Hermaphroditic

Monoecious, internal fertilization, indirect development with complex steps

6. Digestion is incomplete,

Cestoda – no system

7. Nervous System – 1-5 Paired lateral nerve cords & cerebral ganglion Planarian

Platyhelminthes

Characteristics8.20,000 species, about 85% parasitic

9.Excretion - Flame cells

10. Sense organs –

Ocelli = eyespots, Auricles = chemical receptors

Statocysts = gravity, water direction

11. No circulatory, respiratory or skeletal

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MyxozoaMyxozoaMyxozoaMyxozoa

ArthropodaArthropodaArthropodaArthropoda AnnelidaAnnelidaAnnelidaAnnelida

MolluscaMolluscaMolluscaMollusca

LophophoratesLophophoratesLophophoratesLophophorates

HemichordataHemichordataHemichordataHemichordata

ChordataChordataChordataChordata

Other Other pseudocoelomatespseudocoelomates

Other Other pseudocoelomatespseudocoelomates

NematodaNematodaNematodaNematoda

PoriferaPoriferaPoriferaPorifera

CtenophoraCtenophoraCtenophoraCtenophoraCnidariaCnidariaCnidariaCnidaria

PlacozoaPlacozoaPlacozoaPlacozoa

PlatyhelminthesPlatyhelminthesPlatyhelminthesPlatyhelminthesNemerteaNemerteaNemerteaNemertea

CiliophoraCiliophoraCiliophoraCiliophoraSarcomastigophoraSarcomastigophoraSarcomastigophoraSarcomastigophora

MicrosporaMicrosporaMicrosporaMicrosporaApicomplexaApicomplexaApicomplexaApicomplexa

MesozoaMesozoaMesozoaMesozoa

EchinodermataEchinodermataEchinodermataEchinodermata

CrustaceaCrustaceaCrustaceaCrustaceaChelicerataChelicerataChelicerataChelicerata

UniramiaUniramiaUniramiaUniramia

ProtochordatesProtochordatesProtochordatesProtochordates

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AcoelomateAcoelomate

EctodermEctodermMesodermMesodermEndodermEndoderm

No body cavity!

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Phylum Platyhelminthes: Class Turbellaria

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Acoelomate Planarian cross section

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Nervous System

Lateral nerve cordLateral nerve cord

ConnectivesConnectives

AuricleAuricleEye spotEye spot

Cerebral ganglionCerebral ganglion

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Excretory System

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Excretory system continued

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Digestive system

4 Classes of Platyhelminthes

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Class Turbellaria – “Commotion-like” Free living

Class Trematoda(Flukes) – “Perforated form” Endo parasiticClass Monogenea – “ Single Origin”

Most are ECTO parasitesClass Cestoda (Tapeworms) – “Girdle form” Endo parasitic

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1. Class Turbellaria

• Eye spots-OCELLI

• Cilia and slime surface

• Regenerate if cut in two

• Most are free-living

• Found in ponds, streams

and hot springs “FRESHWATER”

• 6 species of terrestrial ones in U.S.

Planaria

• Carnivorous

• Use a pharynx tube to eat

• Regenerative properties

• Chemoreception with auricles

• Light sensitive ocelli

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

Planaria-Dugesia

“Ocelli”

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2. Class Trematoda

“Clonorchis”Chinese liver fluke

• Flukes• Adults-Endoparasites of

vertebrates/several hosts• Holdfast devices

– Hooks/suckers– Glands produce cyst material

• Complex life cycle• Sense organs are poorly developed

SubClass - Digenea

“means double-race

a.Indirect life cycle

1st intermediate host = mollusk (snail)

Final host = vertebrate

b. Tissue attacked: digestive, respiratory,

circulatory, urinary, reproductive

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17Asian Liver Fluke

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Clonorchis sinensis

Oral sucker

Intestine

Uterus

Yolk gland

Testes

Ovary

Seminal recepticle

Asian Liver Fluke

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Clonorchis sinensis• Human/Asian Liver Fluke also

infects dogs, cats, pigs

• 50 million people

• China, Japan, SE Asia

• Live in bile duct can cause Cirrhosis of liver

• Diarrhea, Edema, Pain

• Controlled by killing snails

• Gotten by eaten UNDERCOOKED or raw fish

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General Life Cycle

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A.Egg passes in feces to waterB.Egg hatches into larva called MIRACIDIUMC.Miracidium finds snail, penetrates skin forms SPOROCYSTD. Inside snail, sporocyst produces REDIA asexuallyE. Redia produce CERCARIA with tailsF.CERCARIA emerge from snail and penetrate a second host OR land on vegetation to form METACERCARIA(juvenile flukes)G. Adult grows from metacercaria into JUVENILES when EATEN by the CORRECT DEFINITIVE HOST These are SERIOUS parasites of humans and domestic animals

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Fasciola hepatica• Sheep liver

fluke• Sheep, cattle

and man–Weight loss

• Eat vegetation with metacercaria

“Sheep Liver Fluke”

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Life Cycle of the Sheep Liver Fluke

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Fasciolopsis buski

• Intestinal fluke• 10 million people

• Man and pigs

• Hemorrhage and abscesses of small intestine

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Paragonimus westermani

• Lung fluke

• Carnivores, pigs, rodents and man

• May be fatal

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Schistosoma

• Blood flukes

• 200 million people

• 1 million deaths/year

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Life Cycle of a Schistosome Fluke

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Blood Flukes(Schistosoma)

Causes the disease – “Schistosomis” which infects over 200 million people in Africa,

S. America and the Middle East.

Swim from snails to penetrate skin of humans to liver, intestines, bladder and form

ULCERS, ABSCESSES, BLOOD IN Stool and ABDOMINAL Pain. Worst = eggs that clog organs Causing pain in urination, cirrhosis of the liver,

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Schistosome

• Cercaria have forked tail

“Blood fluke”

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Swimmers Itch – found in Great Lakes

Schistosome dermatitis = Itching but little harm

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3. Class Monogenea

• One host

• Ectoparasites

–Mainly fish

• Opisthaptor

–Attachment to host

Class Monogenea

• Found on fish gills

• Bladders of frogs, salamanders

• Eyes of hippos

• Direct life cycle –

Single host

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4. Class Cestoidea• Tape worms

• No digestive system

• 40 feet long

• Structures:

Scolex, proglottid, strobila

• Monoecious

• 1000 species known

• Two host species

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Scolex

“Head attachment”

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Proglottid

UterusUterus

TestesTestes

OvaryOvary

Yolk glandYolk gland

Vas deferensVas deferens

Seminal receptacleSeminal receptacle

“Packet of reproductive cells”

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Pork Tapeworm (Taenia solium)

More dangerousThan beefTapeworm becauseCysticerci can Breakoff and goTo many organsLike eyes and Brain resulting in Blindness or death

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Taenia saginata

“Beef tapeworm”

Can reachOver 2000ProglottidsEmbryos canLive for up to5 months

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Source: Redrawn From Centers for Disease Control, Atlanta, GA.

Life Cycle of the Broad Fish TapewormDiphyllobothrium latum

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Fish Tapeworm – Diphllobothrium latum

• LONGEST TAPEWORM TO INFECT HUMANS• 65 feet long• Gotten from eating RAW fish/undercooked• US infections are MOST common in GREAT LAKES area• Worm may cause SERIOUS anemia

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Dipylidium caninum“Dog tapeworm”

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Echinococcus granulosus

• Parasite of dogs– Host

• Juveniles in sheep, man and other mammals– Intermediate host

• Hydatid cyst

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Hydatid Cyst

• Cysticercus

–Juvenile stage

–Grows slowly in dogs up to 20 yrs

–Filled with 1000’s of scolex’s

–Surgical removal

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• Adult stage in dog

Echinococcus granulosus

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