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CladeEcdysozoansPhylaNematodaandNematomorpha

Chapter18:387‐396

Nematoda

Everyphylahershedstheircu8cleastheygrow=ecdysis=Ecdysozoa

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Nematoda

•  Marine,freshwater,moistterrestrialenvironments

•  Bilateralsymmetry•  Roundbody•  TriploblasFc•  Pseudocoelomates•  ParasiFzevirtuallyanyanimalandplant.

•  CompletedigesFvesystem

Nematoda

•  CuFcle(hypodermis),whichisshedwhenthejuvenilesgrow

•  Nociliaorflagella•  Donothaveprotonephridia,

excreFonisbyoneormorelargeglandcellsthatopenstotheexcretorypore

•  Muscularpharynx•  Mostaresmall,butparasiFc

speciescanreach1mormore

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Nematoda

•  TheyhavearingofnerveFssueandgangliaaroundthepharynx

•  Twonervecords•  Sensorypapillaeinthehead

andtail

DorsalNervecord

VentralNervecord

Nematoda

•  Mostnematodsaredioecious

•  Malesaresmallerthanfemalesandhavecopulatoryspicules.

•  FerFlizaFonisinternalandeggsareusuallystoredintheuterusunFldeposiFon

•  MostparasiFcspecieshavefree‐livingjuvenilestages.

•  Otherparasitesrequireanintermediatehosttocompletetheirlifecycle

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Hookworms

•  TrichinellaspiralisisoneoftheseveralspeciesthatcausesthelethaldiseaseofTrichinosis

•  AdultwormsburrowinthemucosaofthesmallintesFnewherefemalesproducelivingjuveniles

•  Juvenilespenetratebloodvesselsandareacarriedthroughoutthebody

•  Eventuallytheypenetrateskeletalmusclecellsbecomingoneofthelargestintracellularparasite

Thewormchangesthe‘behavior’ofthecell.Thecellnourishtheworm.ThereisaninflammatoryreacFonaroundthenownursecells.Juvenilesmaylive10‐20years,andnursecellseventuallycalcify

Hookworms

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Filialworms

•  Wucheriabancro1i

•  8sppknowntoinfecthumans

•  LivesinlymphaFcsystemandfemalesareaslongas10cm.

•  Diseasesymptomsinclude:–  InflammaFon–  ObstrucFon

•  Mosquitoisavector

Elephan8asisareproducedaberlongandrepeatedexposuretoreinfecFon.

AnotherfilialwormiscarriedbyblackfliesandcausesblindnessinCentralAmerica,SouthAmerica,Africa,Arabia

Hookworms

•  Enterobiusvermicularis

•  HookwormscauselielediseasebuttheyareamongthemostcommonnematodeparasitesinUSA30%ofallchildren,and60%adults

•  AdultparasitesliveintheintesFneandcecum

Femalesmigrateatnighttotheanustolaytheireggs.

Scratchingtheanusareacontaminateshandsandbedclothes.WhenswallowtheyhatchintheduodenumandmatureinthelargeintesFne

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Nematomorpha

Everyphylahershedstheircu8cleastheygrow=ecdysis=Ecdysozoa

PhylumNematomorpha

•  Horsehairworms•  Poorlyknown•  Extremelylongandslender•  Nocirculatory,respiratory,and

excretorysystems!•  Larvalstageshavehookand

stylets•  Aredioecious•  Inarthropodhoststhey

completeasinglemoltandemergeintowaterasmatureadults.Ifthehostisterrestrialsomehowtheychangetheirbehaviortogointothewater.

Femalesmigrateatnighttotheanustolaytheireggs.

Suicidalcricket!videohep://www.youtube.com/watch?v=Df_iGe_JSzI