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2 Bul.Natl.SalmonResourcesCenter,No.8,26 2 Table1.PrevalenceofMyxoboluskisutchiinandsalmonfrom thecolumbiariverbasinanditsvicinities. Prevalence (%) No.offish infected No.offish examined Dateofcapture Locality River Stage Type Fish Apr.1987 WoodyIslandtestfishery Apr.1987 Corbettestfishery Apr Apr.3, Sep.14, Sep Jun.16-18,1987 JonesBeach Jul.14-18, Jun.21-24, Jun.21-29,Jul.6, May6& 7, May8-1, Feb.5,1991 RoundButeHatchery (DeschutesR.) 6 Mar.6,1991 Warm SpringsHatchery 9 Feb.27,1991 LeavenworthNationalFishHatchery (WenatcheeR.) 54 Mar.27,1991 DworshakNationalFishHatchery (ClearwaterR.) 91 Mar.13,1991 DworshakNationalFishHatchery (ClearwaterR.) 3 Apr.12,1991 DexterPonds (WilameteR.) Mar.12,199 CowlitzSalmonHatchery (CowlitzRiver)? Aug.5,199 HuppSpringsHatchery Sep.23& 3,1996? Apr.12,1996 SimpsonHatchery ChehalisR.(SatsopR.) Aug.5,199 Hatchery Feb.1,1996 Hatchery Apr.11,1996 Hatchery 3 Apr.1996 Hatchery 3 May4,1996 Hatchery Jun.7,1996 Hatchery Jul.3,1996 Hatchery Aug.1996 Hatchery Sep.1996 Hatchery 1 Oct.15,1996 Hatchery Nov.17,1996 Hatchery Jan.1997 Hatchery Mar.1997 Hatchery Apr.1997 Hatchery

3 Urawaetal. Myxobolusksutchifrom salmonidbrains 3 Fig.1.Mapsindicatingsamplinglocations. Table2.SporecharactersofMyxoboluskisutchifrom thecentralnervetisuesofandsalmon. Host No.spores Location (Infectionsite) measured SL *1 SW *1 ST *1 PCL *1 PCW *1 NC *2 SW/SL Springsalmon ColumbiaRiver (medulaoblongata) 1987 (9.-11.)* 3 (8.-9.8) (6.-7.2) (4.-6.) ( ) (.8-1.) Falsalmon ColumbiaRiver (medulaoblongata) 1988 ( )( )(6.2-7.) ( ) ( ) (7-9) (.82-1.) salmon, (medulaoblongata) ( )(8.-1.)(6.-7.2) (4.5-6.) ( ) (.76-1.) Cohosalmon, (medulaoblongata) (8.-1.) ( ) (4.9-6.) (4.-5.2) (2.-3.1) ( ) Cohosalmon, (medulaoblongata) ( ) (7.2-9.) ( ) (4.5-6.) ( ) (6-8) ( ) Cohosalmon, (spinalcord) ( ) (7.-8.6) ( ) ( ) ( ) (6-8) ( ) Cohosalmon *4 (spinalcord) - ( ) (6.5-7.) ( ) ( ) *1SL,sporelength;SW,sporewidth;ST,sporethicknes;PCL,polarcapsulelength;PCW,polarcapsulewidth;inmm. *2NC,numberofcoilsperpolarfilament.*3Mean SD(range).*4Measurementsfrom sectionedmaterialbyyasutakeandwood(1957). halisriver(coastofwashingtontributary)during (Table1,Fig.1).Forthesurveyofseasonal occurenceofparasites,almonreared in the Minter Creek Hatchery were colected monthlyfrom April1996toApril1997.Thesewererearedinpond#17suppliedwithwater from.thewatertemperaturewasrecordeddailyduringthesurveyperiod.seawardmigrating(n=432)werecapturedat andjonesbeachinthelowercolum- biariverintheandearlysummerof adultandsalmonwerecapturedinthelowercolumbiariver(n=295)andin (n=37).thefishsampleswerefrozen orfixedwith1% formalinandstoreduntilthetissueswereexaminedforparasites. Parasiteexamination Themedulaoblongataandspinalcordwereremovedfrom thefishsamplesandsmearedonslides. Thesmearedslideswereexaminedforthepresence ofm.kisutchisporeswithamicroscope(2 magnification).in addition,themonthly samples from thehatcherywereobservedfor

4 Bul.Natl.SalmonResourcesCenter,No.8,26 A B C Fig.2.PhotomicrographsofMyxoboluskisutchi.(A)Sporesinthespinalcordofsalmonfrom thehatchery. Scalebar=25mm.(B)Same.Scalebar=5mm.

detected myxosporeanspores,viewedbyanormanskymicroscope,weredescribedaccordingtoguidelinesproposedbylom andarthur(1989).sporemeasurementsweremadefrom freshspecimens.

kisutchiweredetected amongtheneurofibrilsofthecentralnervetisues (medulaoblongataandspinalcord)ofand salmon,butnotinthelateralperipheral nerve.noapparenthostresponsewasobservedin theinfectionsites.

4 4 Bul.Natl.SalmonResourcesCenter,No.8,26 A B C Fig.2.PhotomicrographsofMyxoboluskisutchi.(A)Sporesinthespinalcordofsalmonfrom thehatchery. Scalebar=25mm.(B)Same.Scalebar=5mm.(C)Sporesinthemedulaoblongataofsalmonfrom thecolumbia River.Scalebar=5mm. parasitesinthelateralperipheralnerve.detected myxosporeanspores,viewedbyanormanskymicroscope,weredescribedaccordingtoguidelinesproposedbylom andarthur(1989).sporemeasurementsweremadefrom freshspecimens. Results Geographicaldistribution Parasite MyxosporeansporesofM.kisutchiweredetected amongtheneurofibrilsofthecentralnervetisues (medulaoblongataandspinalcord)ofand salmon,butnotinthelateralperipheral nerve.noapparenthostresponsewasobservedin theinfectionsites.trohozoites(n=6)wereiregular inshape,usualyelongated, mm in size,andcontained5-23spores(fig.2a).thespore shapewasoviform oralmostroundinthefrontview (Fig.2B,C).Thesporesizewasslightlydiferent dependingonthehostfishes(table2):thespores from salmonweresignificantlylargerthan thosefrom salmon(p<.5).thewidthof shelmembranes was.6-.8 (mean.74)mm (n=1).twopyriform polarcapsuleslocatedatthe anteriorendoccupiedalmostthehalfofthespore length.polarfilamentscoiledinsideforming6-9 loops.thefilamentsextendedwith5% KOHmeasured (mean66.6)mm (n=6).asmaltriangularintercapsularproceswaspresent. Myxoboluskisutchisporesweredetectedinsalmonandcapturedinthelower ColumbiaRiver(Table1).TheprevalenceofinfectioninmigratingseawardpasttheMcNary Dam,whichislocated467km upstream from the rivermouth,was2-37% inmay,droppedto % injune,andincreasedagainto29% injuly. The prevalence of infection in adult salmoncapturedinthelowermainstream ofthecolumbiariverwas43-65% forruns,butlower (8-11%)forruns.Amongsixhatcheriesinthe ColumbiaRiverBasin,theparasitewasfoundonly insalmonfrom thecowlitzsalmonhatchery,where alsalmonexamined(n=5)were heavilyinfected.andsalmonrearedinthehatcheryandthe Simpson Hatchery were also infected with M. kisutchi. Seasonaloccurence InsalmonrearedattheMinter CreekHatchery,sporesofM.kisutchiwerenotpresentinAprilandMay,butappearedinthecentral nervetisuesinjune(fig.3).theprevalenceof sporeinfectionsincreasedto97% injuly,andremainedatalmost1% untilthenext,when fishreachedthetage. Discusion MyxoboluskisutchiwasfirstfoundbyYasukate

5 Urawaetal. Myxobolusksutchifrom salmonidbrains 5 Fig.3.SeasonalchangesinprevalenceofMyxoboluskisutchispores(closedcircles)inalmonrearedattheMinter CreekHatchery.Opencirclesindicatetheaveragerearingwatertemperatureineachmonth andwood(1957),buttheirdescriptionwasbased mainlyonhistologicalmaterials.thepresentdescriptionofm.kisutchiindicatesthatthefreshspore sizeislargerthanthatintheoriginaldescription, eventhoughthehostspecies(salmon)andlocation()werethesame(table2).this isapparentlyatributabletosporeshrinkageduring theprocesingofsectionedmaterials.itisnoteworthythatsporesfrom salmonwerelarger thansporesfrom salmon.hine(1979)alsoobservedvariationsinthesizeandshapeofmyxidium zealandicumsporesamonghostspecies. Severalothermyxosporeansarefoundinthe nervetisuesofsalmonids(schubergandschr`der 195;Pugachev and Khokhlov 1979;Gonzalez- LanzaandAlvarez-Pelitero1984;Hedricketal. 1991).Amongthesespecies,Myxoboluskisutchiis morphologicalyverysimilartom.neurobius.the firstrecordofm.neurobiuswasofspecimensfound inthespinalcordofbrowntrout(salmotruta)in Europe(SchubergandSchr`der195),andlaterM. neurobiuswasalsofoundinseveralsalmonidspeciesfrom thepacificcoastofasia(pugachevand Khokhlov1979;Awakuraetal.1982,1995;Urawa andawakura1994)andtheatlanticcoastofnorth America(Maloneyetal.1991).ThesporesofM. neurobiuswerefoundinthelateralperipheralnerve ofnorwegian brown troutand Japanese masu salmon(o.masou),aswelasinthebrainandspinalcord(urawaandegil,unpublisheddata).however,sporesofm.kisutchiwerenotpresentinthe peripheralnerve tisues of and salmon.thus,weproposethatm.kisutchiremains asanindependentspeciesatthepresenttime.future molecularandlifecyclestudiesarenecesaryfor thetaxonomyofmyxobolusspp.inthenervesof salmonids. Manypapersshow thatthelifecycleofmyxosporeansinvolvesanactinosporeanstageinaquatic oliogochaetesorpolychaetes.forexample,theoligochaetesstylodrilusheringianusandlumbriculus variegatusserveasthealternatehostofm.arcticus, whichinfectsthebrainandspinalcordofsalmonids (Kentetal.1993;UrawaandAwakura1994).We surveyed severalspeciesofoligochaetesin the duringtheearlyfebruaryof1996,but couldnotfindanyactinosporeans.ontheother hand,theseasonalsurveyindicatedthatsporesofm. kisutchiappearedinthecentralnervetisuesofinjune,severalmonthsafterhatching.the prevalenceimmediatelyincreasedtoalmost1% inthenextmonth,andthesporesremainedinthe nervetisuesthroughoutthehostlife.thesporeformationofm.arcticusoccurswithin3monthsafter infectionat1/c(urawaandawakura1994).thus salmonmaybecomeinfectedwithactino-

7 Urawaetal. Myxobolusksutchifrom salmonidbrains 7 Groman.1991.TheoccurenceofMyxobolus neurobius(myxosporea)inwildatlanticsalmon andarcticcharinnewfoundland.j.aquatic AnimalHealth,3: Margolis,L.1982.ParasitologyofPacificsalmonanoverview.InAspectsofparasitology(edited bye.meerovitch).mcgiluniversity,montreal, Quebec.pp Moles,A.,andJ.Heifetz.1998.Efectsofthebrain parasitemyxobolusarcticusonsockeyesalmon. J.FishBiol.,52: Moles,A.,P.Rounds,andC.Kondzela.1991.Use ofthebrainparasitemyxobolusneurobiusinseparatingmixedstocksofsockeyesalmon.am. Fish.Soc.Symposium,7: Pugachev,O.N.andP.P.Khokhlov.1979.MyxosporeansofthegenusMyxobolus-parasitesof thebrainandspinalcordofsalmonidae.insystematicandecologyoffishesinthefareast.pp (InRusian.) Quinn,T.P.,C.C.Wood,L.Margolis,B.E.Riddel, andk.d.hyat.1987.hominginwildsockeye salmon(oncorhynchusnerka)populationsasinferedfrom diferencesinparasiteprevalence andalozymealelefrequencies.can.j.fish. Aquat.Sci.,44: Schuberg,A.,andO.Schr`der.195.Myxosporidienausdem Nervensystem undderhautder Bachforele.ArchivfhrProtistenkunde,6:47-6. Urawa,S.1989.SeasonaloccurenceofMicrosporidiumtakedai(Microsporida)infectioninmasu salmon,oncorhynchusmasou,from thechitose River.Physiol.Ecol.Japan,Spec.Vol.1: Urawa,S.,andT.Awakura.1994.ProtozoandiseasesoffreshwaterfishesinHokkaido.Sci.Rep. HokkaidoFishHatchery,48: Urawa,S.,andK.Nagasawa.1995.Prevalenceof Myxobolusarcticus(Myxozoa:Myxosporea)in fivespeciesofpacificsalmoninthenorthpacificoceanandberingsea.sci.rep.hokkaido SalmonHatchery,49: Urawa,S.,K.Nagasawa,A.Moles,and L. Margolis.1998.Stockidentificationofchinook salmon(oncorhynchustshawytscha)inthenorth PacificOceanandBeringSeabyparasitetags. North Pacific AnadromousFish Commision Bul.,1: Yasutake,W.T.,andE.M.Wood.1957.SomeMyxosporidiafoundinPacificnorthwestsalmonids.J. Parasitol.,43: Wyat,E.J.1978.Anewhostandsiteofinfection formyxoboluskisutchiandhostrecordformyxobolusinsidiosus.j.parasitol.,64: Myxoboluskisutchi LeeHarel ConradW.Mahnken KatherineMyers Myxoboluskisutchi Chehalis McNary M. kisutchi M.kisutchi M.kisutchi

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