mandibular tooth hardness and …下颌牙硬度…

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1、MANDIBULARTOOTHHARDNESSANDMANDIBLEEMPLOYINGBEHAVIORCORRELATEWITHZINCENRICHMENTINADULTLEAFCUTTERANTS,ATTASEXDENSROBERTM.S.SCHOFIELD1*,MICHAELH.NESSON2,KATHLEENA.RICHARDSON11DepartmentofPhysics,UniversityofOregon,Eugene,OR97403,USA,2DepartmentofBiochemistryandBi

2、ophysics,OregonStateUniversity,Corvallis,OR97331,*e-mail:rmss@conch.uoregon.eduThemandibular"teeth",legclawsandotherenvironmentallyinteractive"tools"ofmanyarthropods,aswellassimilarstructuresinsomeannelidsandinatleasttwootherphyla,arehighlyenrichedwithheavymetal

3、sandhalogens,Mn,Fe,Cu,Zn,ClorBr1.WhilemeasuredZnconcentrationsreach25%ofdrymassinscorpionstings,concentrationsareoftenlower;enrichedstructuresarenotheavilybiomineralizedlikevertebrateteethandtheradulaofmollusks1.Forthisreason,thedegreetowhichtheinorganiccomponen

4、tsofthesestructuresmodifytheirmechanicalpropertiesisinquestion.SeveralinvestigationshavefoundahigherindentationhardnessforZnenrichedstructuresthanforsurroundingregions2,3,4,5,6.Thisevidencehasbeeninconclusivebecauseofdifferences,suchasdegreeandtimingofsclerotiz

5、ation,betweenZnrichandsurroundingregions.Here,weinsteadcomparethehardnessofthemandibularteethofleafcutterantsbefore,duringandafterZnincorporation.Usingnanoindentation,wefindthatmandibulartoothhardnesscorrelateswithapproximateZncontent(r=0.91+/0.02).Wesuggestt

6、hatpreviouslyreportedagedifferencesinmandibleemployingbehaviormaybeassociatedwithZnenrichment.ThemolecularformandbiochemistryofZnincorporationisnotknown;Xrayandelectrondiffractometryhavenotdetectedcrystallinityandmetalconcentrationsareoftentoohighforthezincat

7、omstobeboundasindividualionstoproteinbindingsites1.Zincincorporationtakesplacelateincuticulardevelopment:preliminaryhighenergyionmicroprobesurveysfoundmuchlessZninthemandibularteethoflightlycoloredrecentlyeclosedadultleafcutterantsthanintheteethofdarkerolderadu

8、lts7,8.WehaveshownthatZnincorporationalsotakesplacelateincuticulardevelopmentinanotherantspecies(Tapinomasessile)andinaspeciesofscorpion(Vaejovisspinigeris),andwehave