11/16/18 1 Chapter 13 The Smaller Ecdysozoan Phyla Copyright © 2016 McGraw-Hill Educa;on. All rights reserved. No reproduc;on or distribu;on without the prior wriDen consent of McGraw-Hill Educa;on Evolu:onary Perspec:ve – A single morphological feature • Cu:cle – Nonliving – Secreted – Molted periodically (ecdysis) Copyright © 2016 McGraw-Hill Educa;on. All rights reserved. No reproduc;on or distribu;on without the prior wriDen consent of McGraw-Hill Educa;on Figure 13.1 Ecdysozoan Phylogeny. Copyright © 2016 McGraw-Hill Educa;on. All rights reserved. No reproduc;on or distribu;on without the prior wriDen consent of McGraw-Hill Educa;on Phylum Nematoda (Roundworms) • Nematodes are very abundant in species (500,000) and actual numbers (5 billion in an acre of fer:le soil) • Feed on varied carbon sources – RoJng substances – Living :ssues of invertebrates, vertebrates, plants • Great size variability: microscopic to several meters long • Parasites and free living • Lack cilia except in sensory structures • Two classes: Secernentea and Adenophorea – Molecular data suggests the class designa:ons don’t accurately reflect current nematode phylogeny Copyright © 2016 McGraw-Hill Educa;on. All rights reserved. No reproduc;on or distribu;on without the prior wriDen consent of McGraw-Hill Educa;on Phylum Nematoda (Roundworms) • Characteris:cs of the phylum Nematoda: – Triploblas=c, bilateral, vermiform (resembling a worm in shape; long and slender), unsegmented, pseudocoelomate – Body round in cross sec=on and covered by a layered collagenous cu=cle; mol=ng usually accompanies growth in juveniles – Complete diges=ve tract; mouth usually surrounded by lips bearing sense organs – Most with unique excretory system composed of one or two reneMe cells or a set of collec=ng tubules – Body wall has only longitudinal muscles Copyright © 2016 McGraw-Hill Educa;on. All rights reserved. No reproduc;on or distribu;on without the prior wriDen consent of McGraw-Hill Educa;on Copyright © 2016 McGraw-Hill Educa;on. All rights reserved. No reproduc;on or distribu;on without the prior wriDen consent of McGraw-Hill Educa;on Figure 13.2 Phylum Nematoda.
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11/16/18
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Chapter13
TheSmallerEcdysozoanPhyla
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Evolu:onaryPerspec:ve– Asinglemorphologicalfeature• Cu:cle
– Nonliving– Secreted– Moltedperiodically(ecdysis)
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Figure13.1EcdysozoanPhylogeny.
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PhylumNematoda(Roundworms)• Nematodesareveryabundantinspecies(500,000)and
actualnumbers(5billioninanacreoffer:lesoil)• Feedonvariedcarbonsources
– RoJngsubstances– Living:ssuesofinvertebrates,vertebrates,plants
• Greatsizevariability:microscopictoseveralmeterslong• Parasitesandfreeliving• Lackciliaexceptinsensorystructures• Twoclasses:SecernenteaandAdenophorea
– Moleculardatasuggeststheclassdesigna:onsdon’taccuratelyreflectcurrentnematodephylogeny
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PhylumNematoda(Roundworms)• Characteris:csofthephylumNematoda:– Triploblas=c,bilateral,vermiform(resemblingaworminshape;longandslender),unsegmented,pseudocoelomate
– Bodyroundincrosssec=onandcoveredbyalayeredcollagenouscu=cle;mol=ngusuallyaccompaniesgrowthinjuveniles
– Completediges=vetract;mouthusuallysurroundedbylipsbearingsenseorgans
– MostwithuniqueexcretorysystemcomposedofoneortworeneMecellsorasetofcollec=ngtubules
– Bodywallhasonlylongitudinalmuscles
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Figure13.2PhylumNematoda.
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StructureandFunc:on• Nematodesareslender,elongate,cylindrical,andtapered
atbothends• Outer,noncellular,collagenouscu:cle
– Con:nuouswithforegut,hindgut,senseorgans,partsoffemalereproduc:vesystem
– Threelayers:cortex,matrixlayer,basallayer– Maintainsinternalhydrosta:cpressure,providesmechanicalprotec:on,resistsdiges:onifparasi:c
– Generallymoltedfour:mesduringmatura:on• Epidermisorhypodermisisbelowthecu:cle
– Surroundsthepseudocoelom• Longitudinalmusclecontrac:onresultsinundulatory
wavesmovingfromanteriortoposterior– Lackcircularmuscles
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StructureandFunc:on
• Nematodesmayhavelipsaroundmouth– Somehavespinesorteethonornearlips
• Amphidsareanteriordepressionsinthecu:clethatcontainmodifiedciliaandfunc:oninchemorecep:on
• Phasmidsareneartheanus,func:oninchemorecep:on
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Figure13.3NematodeMouthStructure.
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StructureandFunc:on• Nematodepseudocoelomisspacious– Fluidfilled,containsvisceralorgansandformshydrosta:cskeleton
• Completediges:vesystem:mouth,buccalcavity,muscularpharynx,longintes:ne(diges:onandabsorp:on),rectumandanus
• Osmoregula:onandexcre:onofnitrogenouswastes– Glandularsysteminaqua:cspeciesusesventralglandscalledreneUes
– Tubularsysteminparasi:cnematodes,developsfromthereneUesystem
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Figure13.4NematodeExcretorySystems.
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StructureandFunc:on
• Nematodenervoussystemconsistsofananteriorneuralring– Nervesextendanteriorlyandposteriorly,mayconnectviacommissures
• Neuroendocrinesecre:onsinvolveingrowth,mol:ng,cu:cleforma:on,metamorphosis
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StructureandFunc:on• Mostaredioeciousanddimorphic(malesaresmaller)
• Femalesystemhasapairofconvolutedovaries
• Malesystemhasasingletes:s
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Figure13.5NematodeReproduc=veSystems.
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SomeImportantNematodeParasitesofHumans
• Ascarislumbricoides:TheGiantIntes:nalRoundwormofHumans(figures13.6,13.7)
• Enterobiusvermicularis:TheHumanPinworm(figure13.8)
• Necatoramericanus:TheNewWorldHookworm(figure13.9)
• Trichinellaspiralis:ThePorkworm(figure13.10)• Wucheriaspp.:TheFilarialWorms(figures13.11,13.12)
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Figure13.6LifeCycleofAscarislumbricoides.
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Figure13.7Ascarisspp.
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Figure13.8LifeCycleofEnterobiusvermicularis.
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Figure13.9LifeCycleofNecatoramericanus.
Figure13.10aLifeCycleofTrichinellaspiralis.
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Figure13.10bLifecycleofT.spiralis.
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Figure13.11Elephan=asisCausedbytheFilarialWormWuchereriabancroIi.
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Figure13.12LifeCycleofWucheriaspp.
LearningOutcomes:Sec:on13.3
• CharacterizemembersofthephylaNematomorpha,Kinorhyncha,Priapulida,andLoricifera.
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OtherEcdysozoanPhyla
• Membersofthefourremainingphylaareadiversegroupofecdysozoans
• Sharedcharacteris:cswithecdysozoans– Cu:cle– Pseudocoelom– Collar-shapedneuralringaroundpharynx
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PhylumNematomorpha
• CommonlycalledhorsehairorGordianworms• Nematomorphshaveseparatesexesandlackadiges:vesystem
• Thenematomorphbodyisextremelylongandthreadlikeandhasnodis:ncthead(figure13.13)
• Sexualmaturityisachievedduringthefree-livingadultphaseofthelifecycle
• Larvaemustenteranarthropodhost
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Figure13.13PhylumNematomorpha.
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PhylumKinorhyncha
• Kinorhynchsareminutewormslivinginmarinehabitats
• Theirbodiesarecomposedof13or14definiteunitscalledzonites
• Acompletediges:vesystemispresent• Membersaredioecious• Mol:ngoccursduringmatura:onbutceasesintheadult
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Figure13.14PhylumKinorhyncha.
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PhylumPriapulida
• Thisphylumcontainsonly16knownspeciesofcucumber-shaped,worm-likeanimalsburiedintheboUomofmarinehabitats
• Thesexesareseparate• Thecu:cleisrepeatedlymolted
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Figure13.15PhylumPriapulida.
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PhylumLoricifera
• ThephylumLorciferawasdescribedin1983• Thesemicroscopicanimalshaveaspinyhead(introvert),athorax,andanabdomen
• Theyliveingravelinmarinesediments
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Figure13.16PhylumLoricifera.
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