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MutationResearch794(2015)52–56ContentslistsavailableatScienceDirectMutationResearch/GeneticToxicologyandEnvironmentalMutagenesisjournalhomepage::(Cometassay)K.Sowmithraa,N.J.Shettya,∗,S.K.Jhab,R.C.ChaubeybaCentreforAppliedGenetics,BangaloreUniversity,JBcampus,Bengaluru560056,IndiabBRNS—DAE,BhabhaAtomicResearchCentre,Mumbai400085,IndiaarticleinfoArticlehistory:Received15June2015Receivedinrevisedform16October2015Accepted19October2015Availableonline24October2015Keywords:EiseniafetidaGammairradiationCometassayCoelomocytesabstractEarthworms(Eiseniafetida)mostsuitablebiologicalindicatorsofradioactivepollution.Radiation-inducedlesionsinDNAcanbeconsideredtobemolecularmarkersforearlyeffectsofionizingradiation.GammaradiationproducesawidespectrumofDNA.Someoftheselesions,i.e.,DNAstrandbreaksandalkalilabilesitescanbedetectedbythesingle-cellgelelectrophoresis(SCGE)orcometassaybymeasuringthemigrationofDNAfromimmobilizednuclearDNA.E.fetidawereexposedtodifferentdosesofgammaradiation,i.e.,1,5,10,20,30,40and50Gy,andcometassaywasperformedforallthedosesalongwithcontrolat1,3and5hpostirradiationtoevaluatethegenotoxicityofgammaradiationinthisorganism.TheDNAdamagewasmeasuredaspercentageofcomettailDNA.AsignificantincreaseinDNAdamagewasobservedinsamplesexposedto5Gyandabove,andtheincreaseinDNAdamagewasdosedependenti.e.,DNAdamagewasincreasedwithincreaseddosesofradiation.ThehighestDNAdamagewasnoticedat1hpostirradiationandgraduallydecreasedwithtime,i.e.,at3and5hpostirradiation.ThepresentstudyrevealsthatgammaradiationinducesDNAdamageinE.fetidaandthecometassayisasensitiveandrapidmethodforitsdetectiontodetectgenotoxicityofgammaradiation.©2015ElsevierB.V.Allrightsreserved.1.IntroductionAsatomicpowerisgraduallyrecognizedasapotentialenergysourcetosustainfuturehumandevelopment,radiologicalpro-tectionoftheenvironmentwillbecomeanevenmoreimportantenvironmentalsafetyconcern[1].Inthepastdecades,scientificandregulatoryactivitiesrelatedtoradiationprotectionhavebeencon-centratedontheradiationexposureofhumans.Theprincipalviewhasbeenthat,ifhumanswereadequatelyprotected,thenotherlivingorganismswouldalsolikelytobesufficientlyprotectedandotherspecieswouldnotputatrisk[2].Thisviewhasbeenques-tioned,andattentionisnowalsoputonthepotentialeffectsofexposuretoionizingradiationofnon-humanbiota.Thus,theInter-nationalCommissiononRadiologicalProtection(ICRP)considers,thatunderstandingtheeffectsofionizingradiationonnon-humanbiotaisessentialfortheradiologicalprotectionoftheenvironment[1].∗Correspondingauthor.E-mailaddress:shettynj@yahoo.co.in(N.J.Shetty).Inmostcontaminationsituations,themajorityoftheradionu-clideinventoryinterrestrialecosystemsisfoundwithinthesoil;thus,soilinvertebratescanreceivesignificantexternalandinternaldoses[3].Soilanimalshaveasignificantparttoplayintheaccu-mulationandmigrationofradionuclides.Earthwormsareamongtheorganismsthataremostsensitivetotheradionuclides,prob-ablybecauseintimatecontacttheyhavewithsoilconstituentsintheuppersoillayersandtheyalsolackthechitinousexoskeletonofsomesoilinvertebratespecies,whichmayreduceexposurefromexternalradiation[3,4].Thus,earthwormsareusefulorganismsfortheassessmentofenvironmentalinsultsduetotheirroleinvermi-compostingandnutrientcycling.Moreover,theyalsocanactasbioindicatorforthetoxiceffectsofchemicalsinsoils[5–7].Amongthevariousearthwormspecies,Eiseniafetidaisespeciallyappropri-ateforthetoxicitytestsbecauseitcanbeeasilybredonavarietyoforganicwasteswithshortgenerationtimes.TheyhavealsobeenacceptedasstandardorganismsforecotoxicologicaltestingbytheEuropeanUnion[8];OECD[9,10]andincludeditinthelistofref-erenceanimalandplants(RAP)oftheInternationalCommissiononRadiologicalProtection(ICRP)[11,12]andasacandidaterefer-enceorganismfromFrameworkforAssessmentofEnvironmentalImpact(FASSET)[3]tostudytheharmfuleffectofionizingradiation.©2015ElsevierB.V.Allrightsreserved.K.Sowmithraetal./MutationResearch794(2015)52–5653Sofar,mostofthedataobtainedconcernedtheeffectsofionizingradiationonearthwormreproduction.Thesestudieshaveshowneffectssuchasreducedreproductiveability,reducedpopulationsize,changesinthedistributionoflifecyclestages,andreducednumberofspecies[13–15].Ontheotherhand,ionizingradiationsalsoproduceagreatvarietyofDNAlesionsthatcanbetakenasmolecularmarkersforearlyradiotoxiceffects.Infact,lowLETradi-ationsuchasgamma-radiationinteractwithDNAeitherdirectlybydepositionofenergyorindirectlythroughthegenerationofoxygenradicalsandreactiveoxygenspecies(ROS),creatingawidespectrumoflesionsi.e.,DNAdouble-strandbreaks(DSBs),single-strandbreaks(SSBs)andbasedamage.AmongtheseSSBsaremuchfrequentthanDSBs,buttheSSBsaregenerallymorerapidlyrepairedandmostlyerrorfree[16].SeveralmethodshavebeendevelopedtodetectthedamagetoDNAstrands.Thesingle-cellgelelectrophoresis(SCGE)orcometassaycandetectDNAstrandbreaksand