InsectPhysiology

DavidMerritt

NavigationbyOdours

Majorquestions:

• Howdoinsectsusescentstomovethroughtheenvironment?

• Howdoinsectsusescentstoreachatarget?

• Howimportantisscentfornavigationvsscenttoassessfoodquality?

Attributesofodoursasorientationsignals

TransmissionacrossalongrangeTransmissionacrossphysicalbarriersCanbeusedindarknessAbletodiscriminatebasedonvolatilecomposition

SlowtomoveDilutedbydistanceTemporaryLocalisationofsourcecanbedifficult

Comparetheseattributeswithothersensorymodalitiessuchassound,vision,gustation

Odourgradients

• Moleculardiffusioneventuallyleadstoevenconcentration,nogradient

• Butodorantsaredistributedaccordingtodiffusionandfluiddynamics

• Odourplumesareduetothemovementofthemedium(airorwater)accordingtofluiddynamics

• Fluiddynamics,turbulence,rotationsofairmasses,3Dwhirlpoolsoreddies• Filamentsofconcentratedvolatiles–>intermittentdetection

OrientationinOdourPlumes

• Boundarylayerisalayerofreducedmovementadjacenttoasubstrate

• Antennaehaveaboundarylayer,dependingonsizeandsurfacemicrostructure

• Senseorgansinpitsexploittheboundarylayer

• Sacrificerapiddetectionforslowdetectionbutnotsubjecttoshortterminaccuracies

HumidityreceptorsensillainthesacculusIR40aisanionotropicreceptordetectinghumidity

OrientationinOdourPlumes

ChemicalInformation• Presence/absence:switchtovisionwhenasignalisdetected

• Concentrationgradient:howtoknowwhatdirectiontogo?

• Intermittency

Fluidflowinformation• Directionofflowdetectedvisually.Detectfixedpointsinlandscape.Flyinganimalsneedtobeabletodistinguishair-flow

createdbymovementofodourplumefromtheirownmovementwithinthemedium

• Directionofflowdetectedbyothersensorysystemssuchasmechanoreceptors,antennaldeflection

NavigatingOdourPlumes

1. Commonly,animalsmoveupwindorupstreamondetectingodourant

2. Sometimesregularlyturnacrosstheplume

3. Taxesrefertotheabilitytodirectmotionrelativetothesourceofstimulation,e.g.,upordownachemicalgradient.Directedreactions.Chemotaxis

4. Klinotaxis:orientationbyalternatinglateraldeviations(zig-zag)

5. Tropotaxis:orientationbyturningtothemoreorlessstimulatedside

6. Kinesesaregenerallyreservedforsituationsinwhichsomemeasureoflocomotoryoutputincreasesordecreases,buttheresultingmotionisrandomwithrespecttothestimulussource.Undirectedreactions.

Active sensation during orientation behavior in the Drosophila larva: more sense than luck

http://dx.doi.org/10.1016/j.conb.2011.11.008

NavigatingOdourPlumes

Kinesesaregenerallyreservedforsituationsinwhichsomemeasureoflocomotoryoutputincreasesordecreases,buttheresultingmotionisrandomwithrespecttothestimulussource.Theyareundirectedreactions.

Onencounteringadropofsugar-waterahungryflystartsaseriesofturnswhosetightnessanddurationdependsonsugarconcentration.Leadstoanapparent“search”patternthroughklinokinesis

Knowitisnota“real”searchpatternbecauseitpersistsiftheinsectismovedtoadifferentlocation

NavigatingOdourPlumes

Rheotaxis(faceflowdirection)

or

Chemotaxis(lateralgradient)

Chemotropotaxis(simultaneous,spatialcomparisonsofchemicalsignals)

Chemoklinotaxis

Optomotoranemotaxis

Counterturning(=zig-zag)

VickersNJ(2000)Mechanismsofanimalnavigationinodorplumes.TheBiologicalBulletin198:203-212

MethodsfortrackingpathsCockroachchemo-anemotaxis

Rust&Bell(1976)

Malecockroachhaschoicesona“Y-ringglobe”:whenpheromoneinaircurrent,turnstowardthesidereceivingtheaircurrent.chemoanemotaxis

Aretheseexperimentalresultsreliable?Considerdesignoflighting,acclimatisation,experimentalrepeats

Y

Methodsfortrackingpaths

MooreRJ,TaylorG

J,PaulkAC,PearsonT,vanSwinderenB,

SrinivasanMV(2014)FicTrac:avisualm

ethodfortrackingsphericalm

otionandgeneratingfictiveanimalpaths.JN

eurosciMethods225:106-119

FictracdevelopedatQBIallowscameratorecordpathofinsectbyrotatingastyrofoamball.

Insectisfixed.

Openloop(novisualfeedback)vclosedloop(visualfeedback)

Sofarusedforvisualorientationexperiments,notodourorientation.

Fee-movinginsectstrackedusingvideoanalysis

Odour-guidednavigationinAnts

A.Normalpath

B.Leftantennaremoved:veertotheintactside

C.Antennaecrossedthenglued

Tropochemotaxis:simultaneoussampling,twosensoryinputs

Odour-guidednavigationinAnts

Pheromonetrailsareshort-lived,refreshedbyuse

Foragingtrailstendtobetree-like(dendritic)

Possiblypolarisedduetoangleofbranching:

(1) directionistowardfoodsource;antshavechoicesbasedonsimilarangles

(2)nestdirection,oneacuteangleandoneobtuseangle

Y

Odour-guidednavigationincockroach

Antennalength,notbilateralsymmetry,ismostimportantincockroachodourtracking

Animalswithoneantennacantrackodour:noLorRbias

Animalswithlongerantennaeperformbetter

Animalswithsametotallengthofantennaaresimilarinperformance

Samelettersmeansnotstatisticallydifferent

Odour-guidednavigationinMoth

Odourencountered:optomotoranemotaxis:moveupwindascalculatedfromvisualflow

Noodourencountered:counterturn(cast)untilodourdetected->surge

Odour-guidednavigationinMosquitoes

Odour-guidedNavigationinDrosophila

(1) 190msafterencounteringaplume,fliesincreasetheirflightspeedandturnupwind,usingvisualcuestodeterminewinddirection.Duetothissubstantialresponsedelay,fliespassthroughtheplumeshortlyafterenteringit.

(2) 450msafterlosingtheplume,fliesinitiateaseriesofverticalandhorizontalcasts,usingvisualcuestomaintainacrosswindheading.

(3) Aftersensinganattractiveodor,fliesexhibitanenhancedattractiontosmallvisualfeatures,whichincreasestheirprobabilityoffindingtheplume’ssource.

(4) Computermodellingshowedthesedelaysareclosetooptimalforfollowingplume

(E)Examplefrompseudoplumeofcleanair.

(F)Examplefrompulsedethanolplume.

(G)Examplefromcontinuousethanolplume.

vanBreugel,F.andDickinson,M.H.Plume-TrackingBehaviorofFlyingDrosophilaEmergesfromaSetofDistinctSensory-MotorReflexes.Curr.Biol.24,274–286.

http://what-when-how.com/insects/orientation-insects/

MichaelDickinsonTEDtalkc15minhttps://youtu.be/e_44G-kE8lE

vanBreugel,F.andDickinson,M.H.Plume-TrackingBehaviorofFlyingDrosophilaEmergesfromaSetofDistinctSensory-MotorReflexes.Curr.Biol.24,274–286.

LockeyJK,WillisMA(2015)Oneantenna,twoantennae,bigantennae,small:totalantennaelength,notbilateralsymmetry,predictsodor-trackingperformanceintheAmericancockroachPeriplanetaamericana.JExpBiol218:2156-2165

LucaTurinhttps://youtu.be/yzOcvINn8Iw