An experimental study of the refusal display in the damselfly Platycnemis pennipes (Pall.) (Zygoptera: Platycnemididae)

9 Pages·1992·2.1 MB·English

by  Gorb, S

Odonalologica21(3): 299-307 September1. 1992
An experimental study of the refusal display
in the damselfly Platycnemispennipes(Pall.)
(Zygoptera: Platycnemididae)
S. Gorb
DepartmentofInsect Physiology,
SchmalhausenInstituteofZoology, Ukrainian AcademyofSciences,
Lenin Street 15, UKR-252601 Kiev, Ukraine
ReceivedNovember 1, 1991 /Revisedand AcceptedJanuary24, 1992
Femalesintandemorhavingbeenintandem,singlefemales layingeggsandjuvenile
females can demonstrate refusal display to conspecific males and those ofcertain
closelyrelated spp.Refusaldisplayhassomesuccessive statesdependingonthemale’s
persistence.Theresponses ofP.pennipesmalestotherefusal displayby femaleswere
studied by meansof 11 models.These differed in thepresence and position ofthe
abdomen. Female models with abdomens thatrise atanglesof45" and 90" obtained
thelargestnumber ofnegativereactions.Atanextreme state ofrefusal display(abdo-
men rises to maximal angle) the number ofpositive reactions by a male rose, but
seizure ofthe female in tandem washampered.Males demonstrate athreat display
that is similar to female refusal display. In the natural environment threat display
probablydecreases the frequencyofhomosexual contacts, whereasrefusal displayof
females leads toaneconomy ofmaletimeand energy.
INTRODUCTION
Communicationof Odonata images is characterizedby a varietyofkey visual
stimuli.They canbe dividedintotwo alternativegroups;oneofpositive reactions
ofindividuals(attracting)and anotherofnegative reactions (repelling). Thefirst
group ofstimuli takes part in the recognition of sexual partners, for marking
places of oviposition (MARTENS, 1989) and in roosting. The second group
serves for giving signals indicating occupied territory, refusal to pair etc. Such
stimuli canbe purely morphological [i.e. thegeneral body position (UBUKATA,
1983]or thecolorationofabdomenandwings (FRANTSEVICH& MOKRUSH-
OV, 1984)orbehavioural[e.g. wing clapping ofCalopterygidae (B1CK& B1CK,
1978]. The majority of Zygoptera (BUCHHOLTZ. 1956; PAJUNEN, 1963;
300 S. Gorb
UTZERI, 1988)and some Libellulidae(PAJUNEN, 1964;ROBBEY, 1975)hold
theabdomenelevatedwhileperching.Thisposition isobservedamong individuals
ofboth sexes. Forthe femaleitis a display ofrefusal to pair (UTZERI, 1988).
This is welldemonstratedbyfemales,especially juvenile ones, whenconspecific
individualsand/orindividualsofclosely relatedspecies appear.The sameoccurs
infemalesresting afteroviposition, incoldindividualsin theearly morning and
infemales intandem.Theresponseofintruding malestotherefusal display can
bedifferent(ranging fromapairing attempttoanescape or attack). SomeLepido-
pteraandColeoptera haveacomparable refusal display intheirsexual behaviour
(males andfemales ofthe butterfly Thymelicus lineola (Hesperidae) (PIVNIK
& McNEIL, 1985),femalesofthe ladybird beetleHarmoniaaxyridis (OBATA,
1988).Experimental studiesofkey visual stimuli, that exciterefusal display for
pairing in Pieris rapae crucivora (Lepidoptera, Pieridae) femaleswere carried
out by OBARA (1984). A similar investigation of the release of attack by a
territorial male Sympetrum was carried out by FRANTSEVICH & MOKRU-
SHOV (1984).
MATERIALANDMETHODS
Field observations andexperimentswerecarriedoutatthe VorsklaRivernearthe villageNizhnije
Mliny(5 kmfromPoltavaCity)insummer1990. Observationswererecorded inafieldjournaland
onfilm.
EXPERIMENTSWITH MODELS. — Freshlykilled specimenswerepenetratedby a straw that
passed into the thoraxand abdomen and wasfixed toaholder(BUCHHOLTZ, 1956).The following
11 variantsofmodelsweremade(themodels areshownwiththehistogramsinFigs7-17);(1)intact
2, straightabdomen(0°); - (2) 9,threelast abdomensegmentscurved atanangleof45°; — (3)
2,caudal halfofabdomen curvedatanangleof45°; - (4) 2, abdomencurvedatanangleof45°;
— (5) 2, abdomen curved at anangleof90°; — (6) 2, abdomen thrown back overthorax at an
angleof135°; - (7) 2,without abdomen; - (8) 2,abdomenturned downatanangleof45°; —
(9)intact 6, abdomen straight(0°); - (10) S,caudal halfofabdomencurved atanangleof45°;
- (11) 6, abdomen curved atanangleof45°. Wingsofmodels wereintact.
Preparedmodels wereused duringno morethan1-2days(theywerekeptin arefrigeratorbecause
they driedand lost their natural colouration overa longerperiod ofuse). Models were shown to
malesperchednotmorethan 1.5mfromtheedgeofthewater. Observationswerecarriedoutbetween
11.00 and 16,00 h. Such males await females attheperches and thus they demonstrate highsexual
activity. Modelswere presentedinonewayonly (inprofile),becausea ’’facetoface” presentation
usuallyevokedanaggressivereaction(attack,escape).After10-15presentationsmodelswerechanged.
Due tothis, temporalchanges in maleactivity had only aslightinfluence upon therelationshipsof
the various responses. This thesiswascheckedby summingall the male responses recorded forfive
days at a particulartime interval.The mean male responses were then compared forevery time
period.Every model wasshown toevery maleonly once.Registrationwascarriedoutaccordingto
FRANTSEVICH & MOKRUSHOV (1984).Behavioural male responses were registeredasoneof
five reactions:
(1) tandem(t): 6 settlesuponthe modeland seizesitsprothoraxwith theanalappendages;
(2) survey (s): <J flies around the model and settles upon it withoutattemptingtopair;
(3) indifference (i): 6 continues toperch, sometimes demonstratinga threatdisplay;
(4) escape (e); 6 rapidly movesto anotherperch,usually inanoppositedirection fromthe model;
Refusal display inPlatycnemispennipes 301
(5) attack(a): S suddenlyrushes atthe model,usually ’’face toface”.
Altogether 1415reactions (an average of 130belongingtoeach model)wereregistered.
Inseparate experimentsmodels Nos 9, 10,II wereshowntoperchingfemales.
RESULTS AND DISCUSSION
FEMALE REFUSAL DISPLAY
At the bank of the river single females and females in tandem were often
exposed toassaults by conspecific malesandby coenagrionid males (Coenagrion
puella, C.pulchellum, Erythromma viridulum). Juvenilefemalesusually fell into
thegrassin thesecases. Juvenilefemales, females that hadbeefi intandem,and
singlefemales during oviposition (Fig. 1)demonstratedrefusal display.Platycne-
mispennipes hasanextreme
variantofthis behaviour(as
shown by the work of
BUCHHOLTZ (1956)), and
there are somediscretevari-
ants that the femaledemon-
strates depending on male
persistance and the distance
betweenthem(Figs 2-5): (a)
perching female curves up
last 2-3 abdomen segments
(Fig. 3); — (b) femaleraises
theabdomenup to anangle
of 45°, slightly moves the
wings apart and with jerky
Figs 1-5. Platycnemis pennipes (Pall.) movements,foldsandopens
differentsuccessive conditions offemale
refusal display:(I)intandem; — (2)per- them(Fig. 4); - (c) female
ching,straightabdomen; — (3) curving throws the abdomen back
up last 2-3 abdominal segments; - (4) overthethorax,risingon the
femaleraisesabdomenatbaseatanangle hind legs (Fig. 5).
of45°,slightly moves wings apart and Refusal display canbe de-
with the helpofjerky movements folds
monstratedbythefemaledu-
and opens them; — (5)throwingback
abdomenoverthorax,raisingonherhind ringtheflight.She curves up
legs. the abdomen and performs
jerky movements up and
down(Fig. 6).
Females demonstratedre-
fusal displays when male
modelsapproached from the
302 S. Gorb
front or fromone side. The display was espe-
cially vigorous when the models were placed
3-4 cm above her. We did not observe any
escapereaction.Thefemaleresponds by raising
theabdomenandspreading herwings. Thedu-
ration ofpresentation of the male model did
not change the femaleposition. Tactilecontact
intensifiedtheeffect ofvisual stimuli. The fe-
maleraisedthe abdomen vertically andthrew
itforwardsover thethoraxonly in responseto
tactile contact with the model. Sometimes in
this case the female demonstratedescape and
refusal display together. Females do not react
ifmale models are presented from behind.
Fig.6. Platycnemispennipes(Pall.):
femaledemonstratingrefusal display
in flight.
MALETHREATDISPLAY
Wing movements by Zygoptera femalesand males in refusal/threat display
were observed by UTZERI (1988). He supposed thatthis behaviouroffemales
comes from intraspecific imitationofaggressive males by the females. Males
demonstrate such behaviour as a threat display towards other males, or as a
response to females’refusal display. Malescan also demonstratethreatdisplay
by abdomenmovements. Todesignatetheaggressive behaviourofmales, UTZERI
proposed theterm: ’’threat display”and for suchbehaviour in femalestheterm
’’refusal display”. We use these terms inthis paper.
Malesthatperch neartheriverreact by attack totheapproach ofother males.
Afterthis they perform the ’’face to face” behaviour.Then, ifthe intruderflies
away, the resident persues him usually fora distanceof 10-15 cm, after which
hereturnstotheperch or toaplace not farfromit(3-15cm). Sometimesperching
males demonstrate a behaviour that corresponds to female refusal display. It
occurs when the intruderattempts topair withthe resident. This maytake place
in themorning and in theevening whenthe sexualactivity ofsome individuals
is lower.During the daytime homosexualattemptsare ratherrare, but inexperi-
ments with modelsthey are seen more frequently. This can possibly be due to
the fact thatmalemodelscorrespond tomalesonly inoutwardappearance.Model
immobility, the showing ofany modelin profile and the absence ofaggressive
behaviour reduced the attack reaction of a resident (Figs 15-17) and led to
indifferencereactions. In this case we did not distinguish such a reaction from
refusal display.
Refusal display in Platycnemispennipes 303
Figs 7-12. For caption seeFigs 13-17.
304 S.Gorb
Figs 13-17. Platycnemispennipes(Pall.):
malereactions tomodelsofdifferentposi-
tionsoffemale/male (greybars) in com-
parison with reaction to model No. I
(black bars). — [Reactions: T: tandem;
— S; survey; — I: indifference; - E;
escape; - A: attack).
Refusal displayinPlalyenemispennipes 305
Some malescan fly 10-20m along the edge of the water duringtheirtimeof
maximum activity (12.00-15.00 h.), often with nick elevated abdomens. Such
flights are also performed by females from broken tandems (the same refusal
display). In thisway theindividualindicatesto the surrounding malesherrepeal
oftandemformation.
MALE REACTIONSTO DIFFERENTPOSITIONS OFFEMALE
Resultsofexperiments with femalemodels are presented inhistograms (Figs
7-14). From model I to model6 the percentage ofpositive reactions (tandem,
survey) decreaseswhilethepercentageofnegative reactions(indifference,escape.
attack) rises (Fig. 18).Mo-
dels5 and6were themost
effective forcausing nega-
tive reactions of males.
Females without an ab-
domen(7) and withanab-
domen turned down (8)
evokedreactionsthatdiffe-
red slightly from those to
intactmodels(only by per-
centage of indifference).
After vertically raising the
female abdomen and cur-
lingit,theproportionofpo-
sitive reactions rises. This
position hampers the ac-
cess ofthe maleto the fe-
maleandtandemformation
is difficult. In this case
malesdo as follows: fly to
the model from behind,
seize the thorax with the
legs and try to seize the
prothorax withthe analap-
pendages. Such attempts
are usually unsuccessful,
whereas attempts to seize
thethoraxofafemalefrom
thefrontsometimesleadto Fig. 18. Platycnemispennipes (Pall.): dependenceof male
responses onabdomen angles offemale models. In row of
success. Due to this, this models Nos 1-6 abdomen angles increase. - (Reactions:T:
model(6) hasacomparati- tandem; — S; survey: — I:indifference; — E: escape].
306 S. Gorb
vely highpercentageofsurvey reactions. Seizurefromone side (fromabove the
prothorax) led to tandem in more cases. More persistent males had success in
this femaleposition also.
MALE REACTIONS TO DIFFERENTPOSITIONSOFMALE
Only 3 models (9, 10, 11) were used in this experiment. In the lineofthese
models we can also see some displacement to negative reactions (Figs 15-17).
A highpercentageofhomosexualcontacts intheexperiment doesnot correspond
tothesituationin naturewherethey arerare, becausetherearekey visual stimuli
connected with behaviour that serve for male recognition. When the resident
fliesfromtheperch, theintruderdemonstratesitsaggressive behaviourby rushing
atthe resident flying athim ’’face to face”. Ifthis doesnot happen, theresident
maymistake the individualfor a female.We often saw this in our experiments.
Threat displays, between resident and intruder males result in a considerable
lowering ofhomosexualcontacts in P. pennipes.
CONCLUSION
Therefusal display is adynamical behavioural act. Itisevokedby akey visual
stimulus — appearanceofconspecific and coenagrionid males, that display to
the resident one of two reactions; attack or attempt to pair. Experiments with
models cannot reflect the whole spectrum of communicative possibilities of
refusal display because in species with littlesexual dimorphism (Coenagrion,
Ischnura elegans, P. pennipes) the recognition ofa female is connected more
withreciprocal behaviouralreactionsofbothsexesthan withmorphological signs.
Malesdonot react orreact only slightly when femalesdisplay refusalbecause
they are not ready forpairing. As these females are in a zone of many active
mature males, theirbehavioureconomises maletime andenergy.
ACKNOWLEDGEMENTS
My sincere thanks are due to Professor Dr L.l. FRANTSEVICH for critical comments onthe
manuscript. 1thank E. GORB and Dr V.TITARfortheirassistance inthe translation.
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