Observations on the acarofauna of fish aquariums I. Mites associated with Discus fish

16 Pages·2011·0.48 MB·English

Bull. AnnlsSoc. r. beIgeEnt. 123(1987): 87-102
Observations on the acarofauna
of fish aquariums
I. Mites associated with Discus fish
byA.FAIN *and L.LAMBRECHTS**
Summary
Investigationson theacarofaunain5aquariumscontainingDiscusfishes(Symphysodonspp.)
haverevealedthepresenceof3speciesofmitesHydronothrusaquariorumsp.n.(Oribatei),Histios
toma (Ichtanoetus) oce1Jatum sp.n (Anoetidae) and Tyrophagus putrescentiae (Schrank, 1781)
(Acaridae).Theoribatidswerefound harmfulfortheveryyoungfishes.
Resume
Des recherchessurI'acarofaunede5aquariumscontenantdes poissons Discus(Symphysodon
spp.)ontmontrelapresencede3especesd'acariens: Hydronothrus aquariorumsp.n.(Oribates),
Histiostoma (Ichtanoetus) oce1Jatum p.n. (Anoetidae) and Tyrophagus putrescentiae(Schrank,
1781)(Acaridae). H.aquariorumfut trouvepathogenepourlestresjeunespoissons.
Introduction
Only few investigations have been done on the acarofauna living in fish tanks or
aquariums.
HUGHESandJACKSON(1958)recordedtwospeciesofthegenus Histiostoma(Anoeti
dae)fromgoldfishtanks,attheAquariumoftheNewYorkZoologicalSociety.Onewas
Histiostoma cyrtandrae(VITZTHUM, 1931),aspecies described originally from the axil
fluidofawaterflowerCyrtandraglabra(Aracae)fromJava.Theotherwasanewspecies,
H. nigrelliiHUGHES and JACKSON, 1958.
Recently, twonewspeciesofthesamegenus Histiostomahavebeenfound associated
withorparasiticonfish livinginaquariums in Antwerp. Onespecies, H. pisciumFAIN
andLAMBRECHTS,1985hadproducedlesionsoftheswimbladderofaPangasiussutchi,
the other, H. anguillarum FAINand BELPAlRE, 1985, wasfound attached to the gills of
youngeels,Anguillaanguilla.Numerousspecimensofthelastspecieswerealsofoundon
thebottomofthe aquariumcontainingthefish.
ThesefourspeciesofHistiostomafoundinaquariumform asmallgroupbiologically
*InstitutroyaldesSciencesnaturellesdeBelgique,29, rueVautier, B-1040Bruxelles.
** Veterinarysurgeon,KoninginElisabethstraat,8,B-261OAntwerpen.
Manuscritacceptele3mars 1986.
88 Bull. AnnlsSoc. r. beIgeEnt. 123, 1987
and morphologicallydistinctfrom the otherspeciesin the genusand anewsubgenus,
IchtanoetusFAINand BELPAIRE, 1985,wascreatedtoincludeit.
Mitesofothergroupshavealsobeenrecordedfromaquariums,inGermanybyGESH
(1982) andUNTERGASSER(1985).Theseauthorslisted thefollowing mitesfrom aqua
riums: Trimalaconothrus sp. (Oribatei), acarids (Astigmata) and Bdellidae ( Prostig
mata). UNTERGASSERobservedthattheoribatidsareabletoattachtothefish,however
hebelievedthatthesemitesarenotreallyparasiticbutthattheymerelyfeedonthealgae
oronthedecayingmaterialaccumulated onthebottomoftheaquariums.
Inordertofind outtheimportanceoftheacarofaunainaquariumsandtheeventual
pathogenicroleofsomeofthesemites,wehaveexaminedseveralaquariumscontaining
Discusfish(Symphysodonsp.)inAntwerp.Theresultsoftheseinvestigationsarerelated
herein.
Allourmeasurementsaregiveninmicrons(jJ.m).
Material examined
Wehaveexaminedfiveaquariums,allcontainingacoupleofDiscusfish(Symphyso
don spp.) All these aquariums belong to the same owner.Theircharacteristics are the
following:
AquariumnO 1(LBl):
Size: Imx0,4mx0,5 m(height).
Characteristicsofthewater.90mS(electrolytes);pH6,2;KH0,5(carbonatehardness);
Nitrites0,012mg/liter;Nitrates55mg/liter;Temperature30°C.Filtrationmethod:First
filtrationoncotton-woolandsyntheticmoss,finalfiltrationonporcelaincylinders.This
aquariumcontainsacoupleofDiscusfish. Bothmeasured5cm(length)whentheywere
introduced. Themale, oftheTurquoisevariety,is now5years old.Thefemale, ofthe
BrillantTurquoisevariety,is4years old.
Aquarium nO2(LB2)
Size: Imx0,4mx0,5 m(height).
Characteristics ofthe water. 140 mS; pH 6,4; KH 0,5; Nitrites 0,027 mg; Nitrate 38
mg/liter;Temper.28-30°C.FiltrationmethodasfornOIbutfinalfiltrationonlavastone.
The male fish was 5cmlong whenintroduced. Itis now 5years old. Colourvariety
Turquoise.Thefemalewasadultwhenintroduced,ithasbeenintheaquariumfor7years
andis probably9yearsold. Colour: Symphysodon discus .
AquariumnO 3(RBl)
Size:0,7 mx0,6mx0,5 m(height)
Characteristics ofthewater. 550mS; pH7,2;KH 6; Nitrites0,086 mg/liter; Nitrate80
mg/liter;Temper.28°to30°C.FiltrationasfornO2.Themalefishmeasured5cmwhen
introduced;itis now5years old: Colour:Turquoise.Thefemale isan offspringofthe
coupleofaquariumnO Iandisnow2years old. Colour:Turquoise.
Bull. AnnlsSoc. r. beIgeEnt. 123, 1987 89
AquariumnO4(RB2)
Size:0,7mx0,6mxO,5 m(height)
Characteristics ofthe water. 160 mS; pH 6,4; KH I; Nitrites 0,034/liter; Nitrates 65
mg/liter;Temper. 28to 30°C. Filtration asfor aquarium nO 1. Male and female were
introducedaged 1,5years. BothareoffspringofacrossingofaRoyalBluemalewitha
DiscusHeckel
AquariumnO5(RB3)
Size:0,7 mx0,6 mx 0,5 m(height)
Characteristicsofthewater. 120mS;pH5,8;KH I;Nitrites0,011 mg/liter;Nitrates35
mg/liter; Temper. 28 to 30° C. Filtration: motorfiltereheim 2000/u Substrate: Perlon
wooland Nitrex.
ThewaterofthisaquariumhadbeenpermanentlyradiatedwithUVlightbeforethefish
was put in. Itcontained the offspring(a male and afemale) ofa Brown Discus (3rd
generation).Theywereintroducedas adults and are now 1,5years old.
All these Discus fish were fed with a mixture, freshly prepared, offresh ox heart,
deep-freezedspinach,rawfishandacomplexofvitamines(Dagravit).Theyalsoreceived
deep-freezedshrimpsoriginatingfrom brackishwaterinLillo.
ThelengthoftheadultmaleDiscusis16to20cm,thatofthefemaleis2to5cmsmaller.
Results
Thefollowingspeciesofmiteswerefound inthese aquariums:
1. Hydronothrus aquariorum sp. n. (Cryptostigmata, Trhypochtoniidae»: Found in
greatnumbers(morethan 100specimens, adults and immatures)inthe aquariumnO2.
They were less numerous in aquarium nO I (50-60 specimens), nO 3and nO 4(5 to 15
specimensineach)andveryrareinaquariumnO5(I specimen).
2. Histiostoma(!chtanoetus) ocellatumsp.n. (Astigmata,Anoetidae):Thisspecieswas
abundantinaquariumnO3(morethan100specimens,includingfemales,nymphs,larvae
andalsoafewhypopi).TheywerelessnumerousinaquariumsnO4(40specimens),rarein
nO I and5.Theywerenotfound innO2.
3. Tyrophagusputrescentiae(SCHRANK) (Astigmata, Acaridae): Was presentinsmall
numbersCl to5specimens,mostlyadults)inaquariumsnO1,3,4and5.Itistobehoted
thattheaquariumsnO Iand2containednumerouswormsandcrustaceans(Cyclopssp.)
whereas theseinvertebrateswererare orveryrareintheaquariumsnO3and 4.
ThewaterofaquariumnO3wasdirectlyprovidedbytheWaterCompanyofAntwerp.
ItappearsfromthistablethattheOribatids(H.aquariorum)arethemostnumerous in
aquariumsnO I and2whichhavealowpH,and alowcontentofmS, KH, nitritesand
nitrates. Onthecontrary,the Anoetids arerareorabsentin these aquariums, butthey
increaseinnumberwhenthepHandthemineralsreachahigherlevel,asitisthecasein
theaquariumsnO3and4.TherarityofbothspeciesofmitesinaquariumnO5couldbe
explainedbytheverylow pHorbythefactthatthisaquariumhadbeenradiatedwithUV
beforethefishwasputin.
90 BuJl. AnnIsSoc. r. beIgeEnt. 123, 1987
I
Mite fauna Number of
N' of pH and mineral content (number of mite. Worms Crustaceans
pH mS KH Nitri- Nitra in each .am~ (~) (Cyclops)
aquarium tea tea
Oribatid Anoetid
5 5,8 120 1 0,011 35 2 7 7
1 6,2 90 0,5 0,012 55 50-60 5 ++ ++
2 6,4 140 0,5 0,027 38 120-150 0 H' ++
4 6,4 160 1 0,034 65 5-10 40 rare rare
3 7,2 550 6 0,086 80 15 more than rare rare
100
TABLE I: Variations ofthemitepopulations in the5aquariums
Study ofthe species
ORDER CRYPTOSTIGMATA(ORIBATEI)
Genus Hydronothrus AOKI, 1964
HydronothruscrispusAOKI,1964,thetypeofthegenus,wasdescribedfromtheIsland
ofKauai, Hawaii.Themiteswereattached totheleavesofHibiscustiJiaceuslyingunder
waterat 10cmdepth.
A second species, H. puniceusHABEEB, 1981, was described from falls in the north
branch ofthe VenturaRiver, VenturaCo, California, U.S.A.
The normal habitat ofmost ofthe Oribatei is the soil. Some species ofthe families
Nothridae, Malaconothridae, Limnozetidae and Cymbaerenaeidae live in very moist
biotopes(moss,sphagnumetc..).AtrueaquatichabitatisobservedinthefamilyHydro
zetidae whose almost all the members live permanently in water (GRANDJEAN, 1948;
NEWEL, 1948; AOKI, 1964). Two other families contain genera or species completely
adapted to aquaticlife, e.g. Trhypochthoniidae (with genera TrhrypochthonieIlus and
Hydronothrus) and the Ceratozetidae(with HeterozetespaIustris WILLMANN, 1917).
PIFFL,(1978)publishedalistofISspeciesbelongingto9generaofOribatidsoccuring
invarious watercollectionsinEurope.
Keyto the genus Hydronothrus
I.Hysterosomafinelypunctatewithoutanetworkoflines.Presenceofapairofpigmen-
ted eyes. Dorsalsetae not curled. Fromariverin California .
.......................................... H. puniceusHABEEB, 1981.
Bull. AnnIsSoc. r. beIgeEnt. 123, 1987 91
Hysterosomawithadistinct network oflines. Othercharactersvariable 2.
2. Dorsalsetaecurled. Pigmentedeyesand exobothridialsetaelacking. Epimeralsetae
3-0-3-2. Onlythesetae c3insertedonsmalltubercules. FromataropatchonKauai
Island, HawaiianIs. H. crispusAOKI, 1964.
Dorsalsetaenotcurled.Presenceofapairofpigmentedeyesandapairofexobothri
dial setae. Epimeral setae: 3-1-3-2. Setae c3, hI, h2 and ps 1inserted on small
tubercules. FromaquariumscontainingDiscusfish, inAntwerp .
.....................•.......•................• H. aquariorumsp. n.
Hydronothrus aquariorumspec. novo
Thisspecieshas beenfound inseveralaquariumsinAntwerp. All thedevelopmental
stages(adults,nymphsI,IlandIll,larvae)werepresentwhichprovesthatthemitesare
reproducingin the aquariums.
Adults(fig1-3):Holotype51610ngand300wide.Lenghtandwidthin6paratypes:570x
315, 544 x 310, 534 x290,525 x 300, 510 x 255 and 475 x 270. Colour yellowish to
reddish-brown. Prodorsumirregularlyrounded attip, withthreepatchesofverysmall
rounded and clearspots(oneposteromedianand two lateral)Thereisapairofdeeply
situatedpigmentedspots(?eyes)formed ofroundeddarkbrowngranules.These"eyes"
aregenerallysituatedatthelevelofthebothridiumsbutinsomespecimenstheyaremore
anterior. Rostral setaevery thin, 30-35 long. Lamellarsetae very thin, 45 longand 25
apart.Interlamellarsetaestrong,90long.Orificeofbothridiumposterolateral.Sensillus
club-shapedwithagranularcontentinitsdilatedpart,totallenght30.Thereisapairof
thin and short exobothridial sefae. Notogaster. Maximum width slightly behind the
middle.Dorsalsurfacewithadistictreticulatepattern;thecuticleisflatinitsanteriorpart
andslightlyverrucoseinitsposteriorpart.Thereare14pairsofsetae45to60longexcept
the c2andf2shorter(25to30).Setaec3,hI,h2andpsIaresituatedon smalltubercules.
TherearetwopairsofIyrifissures,theanteriorislocatedjustbehindthebaseofc3,the
posteriorisinfrontofh2.Orificeofoilglandjustinfrontoff2.Allthesesetaearesmooth.
EpimeraIregion:Integumentfinelypunctate.Setalformula3-1-3-2. AnogenitaIregion:
Adanal plate with 2pairs ofsetae, the anal plate bears I pairofsetaedifficult to see.
Genitalplatewith9pairsofsetae13to 19long. Legs:alllegstridactyl,themedianclaw
shorterthanthelaterals.LengthoftarsiHV:52-50-54-70.Chaetotaxy:seta[t'thickened
and curved and finely attenuated at apex. TibiaIas in H. crispusexceptthatsetadis
distinctlythickenedinitsbasalhalf.
NymphsI,IIandIIIandlarvae:theyaresmallerandlesssclerotizedthantheadults.
Thebothridiumispoorlydeveloped orabsent. Allthelegsaremonodactyl.
Habitat
Holotypeand30paratypesadults,numerousimmaturesfromthedebrisonthebottom
ofaquariumnO2containingacouple ofDiscusfish(Symphysodon) as wellaseggsof
themandveryyoungfish. Antwerp, December1985.
92 Bull. AnnlsSoc. r. beIgeEnt. 123, 15
1
2
f2
I
ps 1
Figs1-2Hydronothrusaquariorumsp.n.:Dorsalviewofanadult(1);bothridiumandsensilla
Bull. Ann1sSoc. r. be1geEnt. 123, 1987 93
Figs3Hydronolhrusaquariorumsp.n.:Ventralviewofanadult
94 Bull. Ann1sSoc. r. beIgeEnt. 123, 1987
Otherparatypes(adults):20fromaquariumnOIand 10fromaquariumnO3.Holotype in
the InstitutroyaldesSciences naturellesde Belgique.
Pathology
Immediatelyafterhatchingthelarvaeofthefisharemotionless.TheybegintoswinlOO
to200hoursafterthehatching.Oneofus(L.L.)observedthatintheaquariumswherethe
mites are abundant they are regulary found walking on the eggs ofthe fish. After the
youngfisheshatchedthemitesattachedtothem.Theseconddayafterhatchingapproxi
mately30to40%oftheyoungfishes, about4mmlong,arefoundcarry1ngoneormore
mitesontheirbacks.Theparasitizedfishesseemtobeimpairedbythepresenceofthese
mites on their backs and a number ofthem turn in circles, stayingin the same place.
Apparently they are unable to follow their congeners which swim towards the parent
fishes foruptake he mucoidsubstancethattheysecretethrought theirskinand which
representsthemainfood supplyfortheseyoungDiscusfishes.
Acarefulexaminationoftheparasitizedfishesrevealedanabnormalamountofmucus
on their backs at the sites where the mites were attached. After removal ofthe mites
lesions were observed consisting of erosion or even local necrosis of the skin. No
pathologicalactionhas beenobservedin the adultfishes.
,Photographn° I:twomites(Hydronothrusaquariorum)fixed tothebackofayoungDiscusfish.
Bull. AnnlsSoc. r. beIgeEnt. 123, 1987 95
Fromatotal ofabout200eggsobtainedintheseinfected aquariumsabout 100have
hatchedintofishes andfrom these 100fishes only20survived. Wethinkthatthis high
mortalityislargelycaused bythemites'.
Parasitism ofDiscus fishes by oribatid mites had, until now, never been observed,
howeverUNTERGASSER(1985)reportedthepresenceofanoribatidmite, Trimalacono
thrussp.,inaaquariumcontainingDiscusfishes,butthesemiteswerenotfoundattached
to the fish and apparentlywereharmless. This authorobserved thatwhen anotherfish
(Wagtail-Schwerttrligeror?Xiphophorushellen)was introducedinthis aquariumthe
mitesattachedto the mucosaofthesehosts causingimportantlesions.
Anotheraquaticoribatid, Hydrozeteslemnae(COGGI, 1899)has beenfound causing
mechanicalobstructionintadpoles(GRANDJEAN,1949).Thismiteiscommoninwaters
in Europe and it had been found pullulating in great number in a tank containing a
breedingoftadpolesinGeneva,Switzerland.Thesemiteshadinvadedthemouthofthe
tadpolescausingmechanicalobstructionofthepharynx,thuspreventinganormalintake
offood.
Controlofthemites
WehavetriedtocontrolthemiteswithNeguvon.Twodifferentdoseswereexperimen
ted:0,3mgper!iterofwaterwasusedinaquariumscontainingDiscusfishand1mgper
!iterinaquariumswhosefishhadbeenremoved.Inbothcasestheproductwasleftfor48
hoursbeforetorenewthewater.Nomiteswerefoundintheseaquariumsduringthefirst
daysfollowingthetreatment,howeverafter7to10daysthemitesreappeared.Thesource
ofthereinvasionwas notestablished.
ORDERASTIGMATA
FAMILYANOETIDAE
Histiostoma (Ichtanoetus) ocellatumspec.novo
Histiostoma cyrtandraeHUGHES& JACKSON, 1958:59,necVITZTHUM, 1931: 110.
Female(figs 4-12):
Holotype295longand 160wide(idiosoma).Totallengthincludinggnathosoma,338.
Lengthand widthof5paratypes:270x 150;285x 153; 287x163;315x 180;330x190.
Dorsum:Propodosomawithashieldbearingapatternofthinlinespoorlysclerotized.A
pairofsmallnonpigmentedhemisphericaleyelensesarepresentalongthelateralborder
oftheshieldslightlybehindthemiddle. Cuticleofthehysterosoma'softwithouteleva
tions.Thegenitalorificeopensinfrontofasmallpunctatetongue-likeplatelet.Thecanal
96 Bull. AnnIsSoc. r. beIgeEnt. 123, 1987
Figs4-9Histiostoma(Ichtanoetus)ocellatumsp.n.Femaleindorsalview(4);oil-glandpapilla(5);
legIindorsalview(6);apicalhalfoftarsusIinventralview(7);apexoftarsusIindorsalview(8);
chelicerae(9).