2011Cestodes - 10/16/2011 Protozoa: Single Celled Organisms...

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10/16/20111Protozoa:» Single Celled Organisms» EukaryoticPlatyhelminthes -FlatwormsTrematodes, Cestodes-Nematodes– RoundwormsArthropodsCestodesPhylum Platyhelminthes (flatworms)Class Trematoda (flukes)Class Cestoidea (tapeworms)Lack a mouth anddigestive tract.– Subclass Eucestoda (true tapeworms)– Order Pseudophyllidea» GenusDiphyllobothrium,– Order Cyclophyllidea» Genera:Taenia, Hymenolepis, Dipylidium
10/16/20112General CharacteristicsMorphologyMulti-segmented and up to25m long.Scolex- at anterior endfunctions in attachmentNeck- narrowest part of thewormStrobila-made up of segmentsof the worm calledproglottids.
10/16/20113ScolexAcetabulate-has foursuckers or muscular cups.May have an armedrostellum.Bothriate -two, four orsix longitudinallyarranged shallowdepressions
10/16/20114
10/16/20115TegumentLined with microvilli– GlycocalyxMicrothrices (microthrix)Nutrient absorptionTegumental andparenchymal musculature –circular and longitudinalmusclesParenchyma-spaceenclosed by tegumentCestodes have a well developednervous system.A ‘brain’ in scolex is connected via nerves to thestrobila. Reproductive organs and musculature inproglottids are extensively innervated.Osmoregulatory and excretory system- collectingcanals (ventral from scolex; dorsal to scolex)
10/16/20116Reproductive SystemProglottid has male andfemale organsProglottids on the sameworm or another wormcan engage in mating.Anapolyticworms(Diphyllibothrium) tannedeggs exit through uterinepore.Apolyticworms – entiregravid proglottid isreleased – no uterine pore(Dipylidium)EggEgg is encased in a shell• Layeredouter envelope– embryophoreinner envelopeoncosphere - embryo isequipped with hooks andwill give rise to larvalform. Contain vittelinecells as food source
10/16/20117Pseudophyllideaneggs aretanned, have a ciliatedembryophore and have anoperculum at one end. Fromwithin the oncosphere acoracidiumemerges (seen inDiphyllobothrium latum).Dipylideaneggs are thin shelled,have a relatively thick outerenvelope and a non-ciliatedembryophore (DipylidiumandHymenolepis).Taenoideggs lack shell and outerenvelope. Embryophore isoutermost covering (TaeniaandEchinococcus).Life Cycle PatternsPseudophyllidean patternEggs released through uterine poreare expelled in feces.Coracidia emerge and swim aroundin water.

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Term
Fall
Professor
KIMA
Tags
Parasitology, Cestoda, scolex

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