Clade Gnathifera: Rotifera and Acanthocephala

<strong>Clade</strong> <strong>Gnathifera</strong>:<strong>Rotifera</strong> <strong>and</strong> <strong>Acanthocephala</strong>Presumed sister taxa.Form a clade called Syndermata.Have eutelic syncytial epidermis.Constant number of nuclei.Grouping is controversial.

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Phylum <strong>Rotifera</strong>pseudocoelomatethree embryonic germlayers (triploblastic)marine or freshwater,interstitialfree-livingcomplete digestive system

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Lifestyle <strong>and</strong> FormRotifers come in a widerange of colors <strong>and</strong> shapes.– Shapes oftencorrespond to lifestyle(floaters, swimmers,sessile).– They may be individualor colonial.– Mostly freshwater.– Benthic <strong>and</strong> pelagicforms.

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Characteristic featureRotifers have a ciliated crown, the corona,characteristic for the phylum.http://www.youtube.com/watch?v=dlIZGYiajWQ&feature=related

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General Body PlanDigestive tract a continuous tubeGrinding mastaxToes for attachmenthttp://www.youtube.com/watch?v=49RROi71bbA&NR=1&feature=fvwp

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ReproductionDioecious (separate sexes) butsome species parthenogenetic(females produce diploid eggs).Some are parthenogenetic duringpart of the year, depending onenvironmental conditions.Thick shelled eggs that canwithst<strong>and</strong> harsh conditions aresometimes produced.

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Phylum <strong>Acanthocephala</strong>All spiny-headed worms are parasites in the intestines ofvertebrates.Over 1100 species known.Occur worldwide <strong>and</strong> parasitize fish, birds, <strong>and</strong> mammals.Larvae develop in crustaceans or insects.

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<strong>Acanthocephala</strong>n CharacteristicsNo digestive system,nutrients absorbed acrosstegumentProtonephridia <strong>and</strong> flamecellsCovered in syncitialepidermis w/ giant nucleiNo circulatory/respiratorysystem

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Characteristic featureProboscis has rows of recurved spines that penetrate <strong>and</strong>may rupture host intestines.Proboscis with hooks can be inverted into

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Parasitic LifestyleRarely parasitize humans.<strong>Acanthocephala</strong>ns penetrate the intestinal wall withspiny proboscis.!Remarkably little inflammation on host wall, butpain of infection is intense.Larval acanthors burrow through beetle intestine.!Develop into juvenile cystacanths in the insecthemocoel.

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Phylum Gastrotricha• Gastrotrichs appear similarto rotifers, but withoutthe ciliated corona <strong>and</strong>have a bristly lookingbody.• Members of the phylumGastrotricha arepseudocoelomate <strong>and</strong> havethree embryonic germlayers (triploblastic).• Complete digestive system.• Hermaphroditic orparthenogenetic.