©EntomologicaFennica.11October2006 Agonistic behaviour of Scarites buparius (Forster, 1771) (Coleoptera: Carabidae) in relation to body size TeresaBonacci,PietroBrandmayr,AnitaGiglio,AlessandroMassolo,AntonioMazzei, RosalbaOdoguardi,MariastellaRomeo,FedericaF.Talarico&TulliaZettoBrandmayr* Bonacci,T.,Brandmayr,P.,Giglio,A.,Massolo,A.,Mazzei,A.,Odoguardi,R., Romeo,M.,Talarico,F.F.&Brandmayr,T.Z.2006:AgonisticbehaviourofSca- ritesbuparius(Forster,1771)(Coleoptera:Carabidae)inrelationtobodysize.— Entomol.Fennica17:340–344. Intra-maleaggressivebehaviourofScaritesbupariuswasanalysed;agonisticin- teractionbetweenmalesconsistedofarepeatedseriesoffightingevents.Wede- finedthisbehaviouras“agonistic”becauseadominance/submissionstatuswas established.Wemeasuredthemalesandfoundthattheattackbehaviourpersis- tenceiscorrelatedwiththebodylength. T.Bonacci,P.Brandmayr,A.Giglio,A.Mazzei,R.Odoguardi,M.Romeo,F.F. TalaricoandT.Z.Brandmayr,DipartimentodiEcologia,UniversitàdegliStudi della Calabria, 87036 Rende (CS), Italy; *correspondent author’s e-mail: [email protected] A.Massolo,DipartimentodiBiologiaAnimaleeGenetica,UniversitàdiFirenze, viaRomana,17,I-50125Firenze,Italy Received12December2005,accepted22May2006 1.Introduction Agonisticbehaviourisaninherentcapacityof mostanimals.Forinvertebratesithasbeenstud- In the sense of King (1973), “agonistic behav- iedinspiders(Austad1982,1983,Leimaretal. iour”includesallbehavioursassociatedwiththe 1991), cuttlefish and squid (Adamo & Hanlon strugglebetweenindividualsofthesamespecies. 1996,Kingetal.2003),scorpionflies(Thornill Themotororactionpatternsinthepredator-prey 1984) and most exhaustively in crustaceans encounterorininter-specificcompetitionareof- (Hazlett 1981, 1999, Bruski & Dunham 1987, ten the same as those exhibited between con- Copp 1986, Daws et al. 2002, Gherardi & Pie- specificrivals.Thebehaviourissimilar,butthe raccini2004,Goessmannetal.2000,Guiasu& functionoftheagonisticbehaviourchangesfrom Dunham1997,Karavanich&Atema1998).Usu- inter-specificcompetitionandpredator-preyrela- ally,agonisticbehaviouristriggeredbythecom- tionshipstointra-specificsociality.Usually,los- petitionforresources(reproduction,feeding,ter- ers in the agonistic encounter are variously op- ritory ormany amongthem)anditseemstoin- posed,dependingonthespecies;converselywin- crease with the population density (Hazlett nersgainsocialstatusoraccesstoresources.The 1968), and the dominants might hypothetically evolution of restraints to high aggressiveness occupymostofthenichespaceifresourcesarein may buffer a strong negative outcome for the lowdensity(Levins1968).Morse(1974)found loser. that the dominant individuals have larger body ENTOMOL.FENNICAVol.17 (cid:127) Intra-specificaggressivenessinScaritesbuparius 341 sizethansubordinatesinmosthierarchies.Inin- Kiel,Germany).Dataanalysis(frequencyandse- sects,sizeisanimportantcharacteristicdetermin- quence of events) was performed with the soft- ing reproductive success in males (McLain wareTheObserver. 1982).Insoldierbeetleshighersuccessinobtain- ing mates is positively correlated with antennal scape diameter (Mason 1980). Positively varia- 2.2Morphometricanalysis tioninmaledryweightanddiameterofantennae andpalpiinMeloidae(Coleoptera)maycausean The sample consisted of 16 individuals of increasing of the courtship duration (McLain Scaritesbuparius.Magnifiedimagesweretaken 1982). by mean of a stereoscope (Zeiss Stemi SV AgonisticbehaviourinColeopteranshasbeen 11Apo),andimagecapturewasperformedusing poorlyinvestigated;particularlyforcarabidbee- thesoftwareMatroxPC-VCR(Windows2000). tles. S. buparius is one of the first species for For each individual, we measured body length whichintramalefightinghasbeenreportedboth (mm),mandiblelength(mm),headlength(mm), in the field and in the laboratory (Alicata et al. head width (mm), pronotum length (mm), 1980). Recently, Mossakowski (2003) studied pronotum width (mm) and elytral length (mm). the fighting behaviour of Broscus cephalotes MeasurementsweretakenusingSigmaScanPro (L.). In this paper we describe the intramale 5software(SPSS®Inc.). agonisticbehaviouranditsrepertoireofinterac- tions. 2.3.Statisticalanalysis The relationship between morphometric mea- 2.Materialandmethods surements and agonistic behaviour events was analysed by logistic regression (Hosmer & Le- Sixteen specimens (4 females and 12 males) of meshow1989). S.buparius,collectedinsanddunehabitatsonthe WeusedtheSpearmancorrelationcoefficient Ionianseacoast,Squillace,Italy,wereseparately totestforassociationbetweenthedurationofag- kept in glass containers (diameter 5.5 cm, 8 cm gressive behaviour and body size (Siegel & tall),with2cmofsandysoil,inaclimaticcham- Castellan 1998), and then we used nonlinear beratday/nightT24°C/18°C,underL/D:12/12 curveestimationtocomparethefittingofdiffer- photoperiod and fed on Theba pisana (Gastro- entequations(Linear,power,exponential,loga- poda)collectedinthesamehabitats. rithmic,inverse)(SPSS®Base12.0User’sGuide 2003). All statistical analyses were performed with 2.1.Behaviouralanalysis theStatistical Packagefor Social Sciences, ver- sion12.01(SPSS®). EachdyadofS.bupariuswastestedinthelabora- tory(35recordingsessionsintotal)for30min- utes.Animalswerefairly fedbeforetheexperi- ment.Ineachtestonespecimenwasmarkedwith 3.Results non-toxic paint. The experimental arena was a glasscontainerwithaplastersubstrate(8.5cm× After the introduction into the experimental 5.5 cm); the test started when both specimens arena,thebeetlesexhibitedaggressivebehaviour wereplacedinside. with a typical repertoire of eleven interactions Thebehaviourwasrecordedbydigitalvideo (events). equipment (Sony digital video camera and a DVD recorder) and behavioural analyses were (1) Latencyofattack:thetimepassingfromthe carried out with software for behavioural re- introduction into the arena to the attack of search(TheObserver®version2.0,Universityof one of the two rivals (Frequency of occur- 342 Bonaccietal. (cid:127) ENTOMOL.FENNICAVol.17 Fig.1.Agonisticrepertoirein Scaritesbuparius(observedbe- haviouralevents).–a.Mandible grip:oneindividualgraspsthe otherbyitsmandibles.Thisgrip involvesthecontactofanten- nae.–b.Head-pronotumgrip: oneindividualgraspstheother bytheneck(left)orbythe pronotum(right).–c.Pronotum- abdomengrip:oneindividual graspstheotherbythe mesonotum.Thesubordinatein- dividualmayberaisedhead-up (left)orhead-down(right).–d. Defensivegrip:thesubordinate individualgraspswithmandibles theotheronthelegorbythe mandibles. rence(F)=34;x=293.34±370.67sec). behaviourwascarriedoutbymeansofthree o (2) Attack:oneindividualadvancestowardsthe items (mandible grip, head/pronotum grip, other with opened mandibles gripping the pronotum/abdomengrip). opponent’sbody (F =648;x=8.24±8.31 (3) Mandible grip: one individual grasps the o sec). The event “grip” during the agonistic other by its mandibles. This behavioural ENTOMOL.FENNICAVol.17 (cid:127) Intra-specificaggressivenessinScaritesbuparius 343 eventinvolvesthecontactofantennae(F = o 142;x=21.92±72.48)(Fig.1a). (4) Head-pronotum grip: most frequently the dominant grasps the subordinate individual by thehead/pronotumarticulation (a) or by thepronotum(b)(F =149;x=21.71±26.69) o (Fig.1b). (5) Pronotum – abdomen grip: one individual graspstheotherbythemesonotum.Thesub- ordinateindividualmayberaisedhead-up(a) or head-down (b); (F = 133; x = 36.05 ± o 98.62sec)(Fig.1c). (6) Grip-raising:oneindividualgraspstheother withthemandiblesandraisesitfromthesub- strate(F =256;x=26.26±16.52sec). o (7) Defensive grip: the subordinate individual graspswithmandiblestheotheronthelegor onthemandibles(F =82;x=5.65±11.75 Fig.2.Relationshipbetweenmalebodylengthof sec)(Fig.1d). o Scaritesbupariusanddurationofmaleaggressivebe- (8) Skipping: this event was displayed only by haviourinthelaboratory.Blackdots=behaviouraltest the dominant individual; it skips without events;curve=exponentialcurve. movingfromitsposition(F =138;x=9.99± o 24.03sec). (9) Immobility: the subordinate during the grip tack”, one individual approaches the other with remains motionless (F = 219; x = 42.97 ± openedmandiblestogriptheantagonist’sbody; o 96.08sec). “mandiblegrip”,oneindividualgraspstheother (10)Antennal contact: during the fight the indi- by themandibles,whilearapidantennationoc- vidualsinteractviatheirantennae(F =150; cursbetweenthetwoindividuals;“grip”,onein- o x=24.55±36.67sec). dividual grasps the other by various parts of its (11)Escapemovement:oneindividual,duringan body. aggressivebehaviourepisode,escapes(F = Throughouttheagonisticbehaviour,S.bupa- o 590;x=8.2±4.22sec). rius specimens establish the dominant/subordi- nate status. Dominants show superior body Our data showed a significant relation between strength; in particular, they have larger body dominantandsubordinatespecimens.Pronotum length and a wider and longer pronotum. The length(B=28.390;p=0.041),pronotumwidth dominant individual attacks and raises subordi- (B=35.839;p=0.021)andtotalbodylength(B= natesmorefrequentlybutitneverinjurestherival 60.803; p = 0.027) influenced significantly the severely.Conversely,subordinatessuffertheat- acquisitionofthedominance-status.Durationof tack without an aggressive reaction. It is likely aggressive behaviour was positively correlated thatmaleaggressivebehaviourinS.bupariusin- withtotalbodylength(r =0.589,p<0.001),con- volvesreproductivefitness,asvigorousmalesin- s firmedby asignificantexponentialfitting(R2= creasetheprobabilitytofertilizealargenumber 0.334,b =0.594,p<0.001;Fig.2). offemales. 1 Thebodysizeofarthropodsmayevendeter- minetheresultofagonisticencountersbetween 4.Discussion males(Austad1983,Suter1990)and,asaconse- quence,thefecundityoftheinteractingmales. 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