Table Of ContentOdonatologica38(2):133-140 JuneI.2009
Bidirectionalgenderbiasesof gregarine
parasitism in two coexisting dragonflies
(Anisoptera: Libellulidae)
J.L.Locklin* and D.S.Vodopich
DepartmentofBiology,BaylorUniversity, OneBearPlace 76798,Waco,TX 97388,United States
ReceivedAugust18,20081 ReviewedandAcceptedDecember30,2008
Parasitismaffectsalltaxaandinfluences individual andpopulationsuccess.Parasit-
ism ofadult dragonfliesiswidespreadand frequentlyincludes gregarine(Apicom-
plexa)lifestagesinthegutofthehost.Thisresearchinvestigatesvariation ingregarine
parasiteprevalenceandloadinc? versus2 adultsofErythemissimplicicollisandBra-
chymesiagravidaassociatedwith2centralTexasreservoirs incloseproximity.Parasite
prevalencewasbiasedtoward<J6 E.simplicicollis andtoward 92 B.gravida.Results
suggestthat genderbias in parasiteprevalenceis influenced bygenderbehavior and
environment moresothanby immuno-responsedifferences between genders.
INTRODUCTION
Dragonflies processmuchenergyinfreshwaterecosystems as predatorylarvae
as wellasadults.Thesepredators carryaburdenofgregarineintestinalparasites,
but therelationships amongparasite prevalence, load,and host gender are not
wellknown. Becausemalesandfemalesdifferinprofound aspects oftheirbiol-
ogy, wemust consider genders separately to understand host-parasite relation-
ships (i.e. modesoftransmission, prevalence, load,andeffectsonfitness) (ZUK
& McKEAN, 1996). Morphological and/orphysiological sexualdimorphismand
sexualbehaviordifferencesoftenleadtodifferentialexposureandsusceptibility to
parasitism(ZUK & McKEAN, 1996;SCHALK&FORBES, 1997;EDWARDS
& SMITH, 2003).
Genderbiases in parasite prevalence and loadamong vertebrates are better
documented(see ZUK& McKEAN, 1996;CHRISTE etal„ 2007) than forin-
vertebrates. In general, vertebratesexhibit a malebias insusceptibility topara-
*Correspondingauthor:[email protected]
134 J.L.Locklin &D.S.Vodopich
sitism.Aprimary mechanismforthisbias isthe negative effectofandrogens on
the immuneresponse in malevertebrates(GROSSMAN, 1985;ZUK & McK-
EAN, 1996; SCHALK& FORBES, 1997; ROBERTS etal., 2004). Genderbi-
ases are not often observedamong invertebratesbecause they lack androgens
and thereforelack a negative endocrine-immuneresponse (ZUK & McKEAN,
1996). SHERIDAN et al.’s(2000) review of61 studiesinvestigating gender bi-
ases amonginvertebrates, forexample, reports onlynine cases demonstratinga
gender hostbias inonedirectionor theother.
Odonatesare amongthefewinvertebratestoexhibitgender biasesinparasit-
ism (LAJEUNESE, 2007). HECKER et al. (2002) founda femalebias in gre-
garineprevalence inEnallagma boreale,andCANALES-LAZCANOetal.(2005)
reported afemalebias in gregarine loadforE. praevarum. AbRO (1996) found
afemalebias ingregarine loadfor Calopteryx virgo, and LAJEUNESSE etal.
(2004) foundamale bias in prevalence of the ectoparasitic mite,Limnochares
americana,onLeucorrhiniafrigidaandNannothemisbella.Severalstudies(ABRO,
1974; ANDRES& CORDERO, 1998;CORDOBA-AGU1LLAR etal., 2006;
LAJEUNESSE, 2007), however, reportno detectablegender bias inparasitism
ofodonatehosts.
Thepurposeofthis study was to determineif twocommon, coexisting libel-
lulid dragonflies, Erythemis simplicollolis (Say) and Brachymesia gravida (Cal-
vert), havegender biasesashosts for gregarineparasitism, andto discusspoten-
tialmechanismsunderlying genderbiases inodonates.
METHODS
Adult E. simplicicollis and B. gravidawerecollected with an aerial net from tworeservoirs in
McLennan County,Texas,USAfromApril- November 2007.Thereservoirs, Battle Lake(BL),a
small reservoir (0.32km2)with considerable littoral vegetation,and TradinghouseCreek Reservoir
(TCR),alargerreservoir (8.14km2)with little submergedvegetation,are2.5km apart.Weeklycol-
lections fromBL and biweeklycollections from TCR occurredbetween 9:00am- 12:00 pmalong
theshorelines ofbothsites.Nettedspecimenswereplacedinglassineenvelopes andtakentothelab
withintwo hours ofcapture.Inthe lab,theirabdomens wereseparatedfromthe thoraxand stored
in 70%ethanol.
Toquantifyparasiteprevalenceandload,thepreservedabdomens wereplacedventral-side upon
aStyrofoamtray. Theabdomens weresplitlongitudinallyand pinnedto expose the crops and in-
testines. Gregarines(trophozoites and gamonts)werevisible throughtheintestinal epitheliumand
counted at60x magnification.
Parasiteprevalenceswerecomparedbetweenmalesandfemalesofeachspeciesusingcontingency
X2tests (a=0.05).Gregarineloads werecomparedbetween gendersofeachspeciesusingthenon-
parametricWilcoxon RankSum Testbecausetheparasiteload data werenotnormallydistributed
(Shapiro-Wilktest,p<0.001).
Bidirectional genderbiases ofgregarineparasitism 135
RESULTS
Combinedcollections at BLand TCR yielded 1,368 adults(E. simplicicollis.
9 N = 327, 6 N = 801; B. gravida, $ N= 150, S N = 84). Weekly collections
atBLwheredragonfly populations weremoreabundant(personal observation)
produced largersample sizes forbothspecies (BL: E. simplicicollis, 2 N = 260,
(JN = 760; B. gravida, 9 N =95, S N =56) compared toTCR (E. simplicicol-
lis, 9 N =67, 6 N =41;B. gravida, 9 N =55, 6 N = 28).
Analysis of combineddatafor the BLand TCR populations ofeach species
revealedstrong gender biases in gregarine prevalence forB. gravida (x2- 12.07,
p=0.001) and forE. simplicicollis {\2- 14.81, p<0.001). However, thegender
biaseswere inopposite directionsforthetwo species. FemalesofB. gravida had
a significantly greaterparasite prevalence (67%) thanthe males(44%). In con-
trast, malesof E. simplicicollis had a greaterprevalence (46%) thanthefemales
(34%)(Fig. 1).Whenparasite prevalences forbothhostspecies wereanalyzed at
BLandTCR separately, thefemalebias forB. gravidawas consistentatthetwo
sites (BL: x2= 12.97,p<0.001, TCR: \2= 5.41, p = 0.02), butthe malebias for
E. simplicolliswas true only fortheBLpopulation (x2=5.87, p=0.015) andnot
thepopulation atTCR (\2= 1.03,p=0.309)(Tab. I).
Incontrastto significant genderbiasesforparasiteprevalence, meangregarine
loadsdidnotdifferbetweengenders withineach species (.B. gravida: Z=-1.722,
Fig. 1.Frequencyofadultodonatesinfectedwithoneoremoregregarineparasites.DataforB. grav-
ida and E.simplicicollis arecombined samplesfrom two central Texasreservoirs. Numbers above
bars represent samplesizes.
136 J.L.Locklin&D.S.Vodopich
TableI
Comparisonofgregarineprevalenceinthe gendersofBrachymesiagravidaand
Erythemissimplicicollis
SSppeecciieess SSiittee GGeennddeerr NN PPaarraassiittee xX22 PP
pprreevvaalleennccee
BB..ggrraavviiddaa BBLL MMaallee 5566 ..6611 1122..9977 <<00..000011
FFeemmaallee 9955 ..8866
TTCCRR MMaallee 2288 ..1111 55..4411 00..0022
FFeemmaallee 5555 ..3355
CCoommbbiinneedd MMaallee 8844 ..4444 1122..0077 00..000011
FFeemmaallee 115500 ..6677
EE..ssiimmpplliicciiccoolllliiss BBLL MMaallee 776600 ..4499 55..8877 00..001155
FFeemmaallee 226600 ..4400
TTCCRR MMaallee 4411 ..0055 11..0033 00..330099
FFeemmaallee 6677 ..1100
CCoommbbiinneedd MMaallee 880011 ..4466 1144..8811 <<00..000011
FFeemmaallee 332277 ..3344
p— 0.085; E.simplicicollis:Z—0.235, p=0.814) (Fig. 2). Meangregarine loads
forB. gravida andE. simplicicolliswere8.82and 7.73, respectively.
DISCUSSION
At BattleLakeandTradinghouse CreekReservoir, thefemaleparasitism bias
of B. gravida was significant, yetprevalence was notably differentatboth sites
(BL: 9 86%, 6 61%; TCR: 9 11%, 6 35%). Becausethese sites differin size,
they likely havedifferentphysicochemical properties. Although such properties
were not measuredinthis study, themagnitude oftheprevalence differencesbe-
tween the two sites suggests thathabitat/environmentalfactors likely influence
themaintenanceandtransmissionof gregarines withindragonflycommunities.
Maleandfemaleanimalshavedifferentbehaviorsassociatedwithfeedingand
reproduction, resulting indifferentialexposureand susceptibility to parasitism
(POULIN, 1996;ZUK & McKEAN, 1996;SCHALK &FORBES, 1997; ED-
WARDS&SMITH, 2003; CHRISTEetal., 2007). Consequently, parasite suc-
cess canvarywithinconspecifics duetohost genderdifferencesinencounter rates
as wellas the effectivenessof theirimmuneresponses (see ZUK & McKEAN,
1996; HECKER et al., 2002; CHRISTE et al., 2007; LAJEUNESSE, 2007).
Such gender differencesoften result in differential feeding locationsand rates
thatmayincrease ordecreasethe probabilityofingestingthetransmissionstage
and/orshiftenergyallocationawayfromimmunitytowardsreproduction (ZUK
& McKEAN, 1996).
Variationin immune responses between genders may underlie host gender
Bidirectional genderbiasesofgregarineparasitism 137
biases in parasitism. Most studies ofmammals(ZUK & McKEAN, 1996; see
CHRISTE etal.,2007) reportamalebias inparasite prevalenceand loadcom-
pared tofemales.Thisbias isusually attributedto thenegative influenceofster-
oidhormones(e.g. testosterone) onthe immuneresponse. Insects, however, do
notproduce testosteroneandconsequently lackthisendocrine-immuneinterac-
tion.Thereforemaleandfemaleinsectstypically donotdifferinparasite preva-
lenceorloadduetoimmunocompetence (SHERIDAN etal.,2000).Althoughwe
founda gender bias inbothodonatespecies studied, thebiaseswereinopposing
directions,andparasite loadsdidnot differbetweenmales andfemales forboth
species. If thegender biaseshadbeeninthesame directionforbothspecies or if
parasiteloadshaddiffered, thenit wouldindicateanimmunocompetence differ-
encebetweenodonategendersandresultinauniversalgenderbiasofparasitism,
i.e.amaleorfemalebias.Thiswasnotthecase, however.Ourresultssuggestthat
immunocompetence doesnot differbetweengenders ofthese twoodonatespe-
cies, oris specifically ineffective against gregarine parasites foreitherhost gen-
der. CORDOBA-AGUILAR etal.’s (2006) study may support thelatter. They
foundno genderbias ingregarine prevalence orloadinHetaerinaamericanaand
Argiatezpi, butbasedontwo parameterscommonly usedtoestimateaninsect’s
immunesystem, phenyloxidase and hydrolyticlysosomal enzymeconcentrations
(SCHWARZENBACH & WARD, 2006; CORDOBA-AQUILAR etal.,2006),
femalesweremore immunocompentent thanmales.
Anotherexplanation forhost genderbiasesassociatedwithparasitism isvari-
ation in hostexposure to the infective parasite stage.If bothgenders ofaspe-
Fig. 2.Meangregarineloadsforcombined samplesofinfectedodonatesfromtwocentralTexasres-
ervoirs. Errorbarsare± 95%confidence intervals.
138 J.L.Locklin& D.S.Vodopich
ciessharehabitats forforaging and havesimilar immuneresponses, thenpara-
site prevalence and loadpatterns should besimilarbetweengenders (CANAL-
ES-LAZCANA etal.,2005). However, gender-specificbehaviormayexpose one
gendertotheparasite’sinfectivestagesmoreso thantheothergender.TINSLEY
(1989) foundthatflukesmore heavily parasitize malespadefoot toads because
malesspendmostoftheirbreeding seasoninwater,whereasfemalesvisitthewa-
teronlybriefly to layeggs.Suchbehavioraldifferencesin odonatespecies could
resultinthebidirectionalgender biasesfoundinthisstudy. Although general be-
haviorhasbeen describedforE.simplicicollis(PAULSON, 1966;McVEY, 1981;
MAY& BAIRD, 2002), littleisknownabout B.gravida. Onlyonestudy(PAUL-
SON, 1966) briefly describesthe behaviorofthelatterspeciesandincludeslittle
gender-specific information.Withoutadequatebehavioral descriptions forboth
species, it’s difficult toclarify ifthebidirectional gender biasesin thesetwo spe-
ciesresult fromdifferentialgenderexposureto theparasites.
Afinalquestion elicitedby hostgender biases considersmechanismsofpara-
sitepreference (an innateandactive selectionofaspecific hostto maximize fit-
ness). Inmost cases ofgender bias, parasites exhibitsome degreeof preference,
as inthe ectoparastic mites parasitizing manyodonatespecies. Larvalmitesat-
tachphoretically to thefinalodonateinstarinthewater.Astheodonateemerges,
the larvalmite transfers to the teneraland feeds onbody fluids(ROLFF et al.,
2001). Afterfeeding, themitedetaches, falls back intothewater,andcompletes
its development (GRANT& SAMWAYS, 2007). Becausethesemitesdepend on
aquatichabitatsforlifecyclecompletion, it’sadvantageous toattachtoahostthat
eitherstaysaroundwater orreturnsto itforreproduction. Severalinsectstudies
(seeEDWARDS&SMITH, 2003)reportgreatermiteparasitismonfemalehosts
becausefemalesusually returnto waterforovipositing. McLACHLAN’s(1999)
reportthatmitesonmalechironomidsoftenmovetofemalesduring copulation
supportsthis hypothesis.
Whether gregarine parasites prefer aparticular host gender is not clear.Gre-
garine preference maynotbepossiblebecausetheoocystsoftheseintestinalpar-
asites are ingested indiscriminately by apotentialhost(CLOPTON etal., 1992).
Theparasite wouldbestcomplete itslifecycle inthegender thatspends themost
timenearwater. Butselection ofthathost gender wouldonly berealized if the
sporozoites in the ingested oocyst fail to excyst in an unpreferred hostand in-
steadpass throughthe digestive tract,return to theenvironment,andremainvi-
able.CLOPTON et al. (1992) reported that some gregarine species are specific
not onlyto a hostspecies, but also to thehost’slife cycle stage. Excystation as-
says bySMITH&COOK (2008) show thatgregarine excystation is species-spe-
cificincockroaches. Although nostudiesquantify theconcentration/availability
ofoocysts intheaquatic habitat, orthesuccess rate ofparasite transmission for
gregarines, weassume that failuretoexcyst in an unpreferred gender wouldbe
arisky strategy fortheparasite. Its ingestion intoasecondpotential host ofthe
Bidirectional genderbiasesofgregarineparasitism 139
preferredgendermaybeimprobable. Inaddition,theabsenceofa gregarineload
differencebetweenthe genders ofbothspecies indicatethatgregarine parasites
lack theabilityto discriminatebetweenthegenders oftheirhosts, orsimply have
nopreference.
Theenvironment, gender-specific hostbehavior, host immunity,and parasite
preference all regulate parasite loadandprevalence (ZUK & McKEAN, 1996;
SCHALK&FORBES, 1997).Thecontrasting gender biasesfoundinthisstudy
donot fullydistinguish among thesefactors. They do, however, bring focus to
somepaths forresearch investigating factorsassociatedwith theoccurrence and
maintenanceofgregarine parasites inodonatecommunities.
ACKNOWLEDGEMENTS
We thankDAVIDCUMMINGS forassistancein thefieldand lab. Weappreciatethecomments
ofED MORGANonearlydraftsofthismanuscript.
REFERENCES
AERO,A., 1974. The gregarineinfection in different species ofOdonata from the samehabitat.
Zool. Scripta3: 111-120.
ABRO,A., 1996, Gregarineinfection ofadult Calopteryxvirgo L. (Odonata: Zygoptera).J. nat.
Hist. 30: 855-859.
ANDRES, J.A.&A.CORDERO, 1998. Effectsofwatermitesonthe damselflyCeriagriontenel-
lum. Ecol. Ent. 23: 103-109.
CANALES-LAZCANO J„J.CONTRERAS-GARDUNO, &A. CORDOBA-AGUILAR, 2005.
Fitness-related attributesandgregarineburden inanon-territorial damselflyEnallagmaprae-
varumHagen(Zygoptera:Coenagrionidae).Odonatologica34: 123-130.
CHRISTER,A.MAEDER,P.PATTHEY,R.ARLETTAZ,P.VOGEL,G.YANNIC,G,EVANNO,
O.GLAIZOT,G.DEVEVEY,& N.BRUYNDONCKX,2007. Hostsexand ectoparasites
choice: preferencefor, and highersurvivalonfemale hosts.J. Anim.Ecol. 76: 703-710.
CLOPTON, R.E., J. JANOVY,JR.,& T.J. PERCIVAL, 1992. Hoststadium specificityin the gre-
garineassemblageparasitizingTenebrio molitor. J.Parasitoi 78: 334-337.
CORDOBA-AGUILAR A., J.CONTRERAS-GARDUNO, H.PERALTA-VAZQUEZ,A. LU-
NA-GONZALES,A.I.CAMPA-CORDOVA,&F.ASCENCIO,2006.Sexual comparisons
inimmuneability, survival, andparasiteintensityin twodamselflyspecies. J.Insect Physiol.
52: 861-869.
EDWARDS, D.D.&H.G. SMITH,2003, Host sexpreferenceand transmission successbythe wa-
termite Unionicola foli (Acari:Unionicolidae)parasiticonthemidgeChironomus tentans
(Diptera:Chironomidae).J. Parasitoi. 89:681-685.
GRANT,P.B.C.& M.J.SAMWAYS,2007.Ectoparasiticmites infestcommonandwidespreadbut
notareand red-listed dragonflyspecies.Odonatologica36: 255-262.
GROSSMAN, C.J., 1985. Interactions between thegonadalsteroidsand the immunesystem. Sci-
ence227: 257-261.
HECKER K.R.,M.R.FORBES, &N.J.LEONARD, 2002. Parasitism ofdamselflies (Enallagma
boreale)by gregarines:sexbiases and relations toadultsurvivorship. Can. J. Zool.80: 162-
168.
LAJEUNESSE, M.J.,M.R.FORBES,&B.R SMITH,2004.Species and sexbiasesin ectoparasit-
140 J.L.Locklin &D.S.Vodopich
ismofdragonfliesbymites. Oikos 106: 501-508.
LAJEUNESSE, M.J., 2007. Ectoparasitismofdamselflies bywatermites in central Florida. Fla
Ent. 90:643-649.
MAY,M.L.&J.M.BAIRD, 2002.Acomparisonofforagingbehavior intwo“percher”dragonflies,
Pachydiplaxlongipennisand Erythemissimplicicollis(Odonata;Libellulidae).J.Insect Be-
hav. 15:765-778.
McLACHLAN,A., 1999.Parasites promotematingsuccess:thecaseofamidgeandamite. Anim.
Behav. 57: 1199-1205.
McVEY,M.E., 1981.Lifetimereproductivetacticsinaterritorial dragonfly.Erythemissimplicicollis.
UnpublishedPh.D. dissertation,Rockefeller Univ.,NewYork.
PAULSON,D.R., 1966. The dragonflies(Odonata: Anisoplera)ofsouthern Florida. Unpublished
PhDdissertation. Univ. Miami.Coral GablesFlorida.
POULIN, R., 1996. Sexual inequalities in helminth infections: a cost ofbeing amale? Am. Nat.
147:287-295.
ROBERTS, ML., K.L. BUCHANAN, & MR. EVANS, 2004.Testing the immunocompetence
handicaphypothesis:areview oftheevidence. Anim. Behav. 68: 227-239.
ROLFF, J„P.BRAUNE & M.T.SIVA-JOTHY.2001. Ectoparasitesdonot affectejaculatevolume
in thedragonflyCoenagrionpuella.Physiol. Ent. 26:315-319.
SCHALK,G.&MR.FORBES, 1997. Male biasesinparasitismofmammals:effectsofstudytype,
hostage, andparasitetaxon.Oikos78: 67-74.
SCHWARZENBACH,G.A.& P.I.WARD,2006.Responsestoselectiononphenoloxidaseactivity
in yellowdungflies.Evolution 60: 1612-1621,
SHERIDAN.L.A.D.,R.POULIN, D.F.WARD,& M.ZUK, 2000.Sex differencesinparasiticin-
fections amongarthropodhosts:isthereamalebias? Oikos88: 327-334.
SMITH,A.J.&T.J. COOK,2008.Hostspecificity offive speciesofEugregarinidaamongsixspecies
ofcockroaches(Order:Blattodea),Comp.Parasitol. 75: 288-291.
TINSLEY,R.C., 1989. Theeffects ofhost sexon transmission success.Parasitol. Today5: 1106-
1113.
ZUK,M.&K.A.McKEAN, 1996. Sexdifferencesinparasiticinfection: patternsandprocesses. Int.
J. Parasitol. 26: 1009-1024.
