Orientation and rate of locomotion of individual amebas in the life cycle of the cellular slime mold Dictyostelium mucoroides☆

[摘要] 1.1.RateoflocomotionofindividualamebasofthecellularslimemoldDictyosteliummucoroidesweremeasuredthroughoutthelifecycleandconsiderablevariationwasfoundfromonestagetothenext.However,whenindividualamebaswereisolatedfromvariousstagesofthelifecycletheirmeanratesoflocomotionfellintooneoftwocategories;prefeedingamebaswereconsistentlyslow,whereasamebasfromallotherstagesshowedasimilarhighrateoflocomotion.2.2.Therewasnosignificantdifferencebetweenthemeanratesoflocomotionofindividualamebasisolatedfromdifferentpositionsalongthemainaxisofmigratingpseudoplasmodia.3.3.Rateoflocomotionappearedtobedirectlyrelatedtothefrequencyofpseudopodformation.4.4.Rateoflocomotionwasfoundtobeindependentofthesizeoftheameba.5.5.Ofallthephysicalfactorsintheenvironmentnormallyencounteredinlaboratoryprocedures,wetnessofthesubstratewasfoundtobethemostsignificantforitgreatlyincreasedtherateoflocomotionoftheamebas.Theincreaseinspeedwaseffectedbyproducingmoreelongatedpseudopodsratherthanbyalteringthefrequencyofpseudopodformation.6.6.Examinationoftheroleofthechemicalconstitutionofthemediumrevealedthatpeptoneandaminoacidsmaintained,whereasdextroseinhibited,therateoflocomotionofisolatedamebasoveraperiodoftime.7.7.Isolatedamebasshowedclear-cutorientationtowardE.colialthoughthepresenceofthebacteriadidnotaffecttheirmeanrateoflocomotion.8.8.Isolatedamebaswanderawayfromoneanother;theyexhibitadefinitenegativechemotaxis.9.9.Thepresenceoflargequantitiesofpostfeeding(butnotyetaggregating)amebasdoesnotaffecttherateofmovementofisolatedamebasofthesamestage.However,thisisnottrueofrecentlygerminatedamebas,whoserateisincreasedbythepresenceofotheramebas.10.10.Themeanrateoflocomotionofisolatedamebasfromnonaggregatingphasesofthelifecyclewerenotinfluencedbyacrasinwhenactivelysecretingcentersofaggregationwereplacedintheirmidst.11.11.Inpreaggregationandaggregationphasestherewasacorrelationbetweenorientationandthereductionoftherateofmovement.Thesecoupledphenomena,inthecaseofthepreaggregationstagesofD.purpureum,occurredasawaveoriginatingandmovingawayfromanormal-appearingcellbeforethereisanysignoflocalcrowding.InD.mucoroides,thisslowingalsoprecededtheperiodofconspicuouscontact.12.12.Theseresultsshowthatoverandabovethewell-knownorientationmechanismofacrasinthereareanumberofotherimportantsystemsofcommunicationbetweenthesesocialamebas.Thesesystemsinvolverelationsbetweenamebasthataffectrateoflocomotionandorientationaswellasrelationsbetweentheamebasandtheirenvironment.

[学科分类] 生物科学（综合）