Pheromone

Pheromone is a chemical secreted by an animal that influences the behavior or development of other members of the same species

1. By-
Dr. DineshC. Sharma
Head, Zoology
K.M. Govt. Girls P. G. College
Badalpur, G.B. Nagar
[email protected]
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2. 2
Pheromone:achemicalsignal
transmittedbetweenindividuals
ofthesamespecies.
From2Greekwords:
•pherein,totransfer
•hormōn,toexcite

3. Pheromones
Donotfitdefinitionofatrue
hormone
Producedbyoneorganism,travelby
airandaffectasecondorganism.
Examplemuskoil,sexualattractant
ininsects,etc.
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4. 4
Pheromone isachemicalsecretedby
ananimal thatinfluences the
behaviorordevelopment ofother
membersofthesamespecies.Queen
bees,forexample, giveoffa
pheromone thatprevents other
femalesinthehivefrombecoming
sexuallymature,withtheresultthat
onlythequeenbeematesandlays
eggs.Inmany animal species,
pheromones areusedtoestablish
territoryandattractmates.

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Apheromone(inanyanimal):
•Achemicalsignalbetween
membersofsamespecies
•Behaviouraland/orphysiol
response
•Samemol(s)ine.g.allmalesofthe
species(butpossdifferentamounts)
•Usuallyacombinationofmolecules
•Detectedbysenseofsmell(usually)

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Pheromonesare…
“moleculesthatareevolvedsignals,in
definedratiosinthecaseofmultiple
componentpheromones,whichare
emittedbyanindividualandreceived
byasecondindividualofthesame
species,inwhichtheycauseaspecific
reaction,forexample,astereotyped
behaviororadevelopmentalprocess”

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Invisiblesignals
•AncientGreeks :femaledog
•17thC :beekeepingmanual
•19thCJ-HFabre:moths
CharlesDarwin(1871)Thedescentofmanandselection
inrelationtosex
“Duringtheseasonoflove,amuskyodourisemitted
by…glandsofthecrocodile,andpervadestheir
haunts.”
Also:smellymaleelephants,goats,pythons,birds…
Gradualevolutionofmalescentglandsbyfemale
choice-Successofthesmelliest

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Surelythesesmellswerechemicalsignals…butthe
quantitieswerefartoosmalltoidentify(pico/micro
gramperindividual)
Firstpheromoneidentification:1959femalesex
pheromoneofsilkmothBombyxmoribyAdolf
Butenandtet.al
Wingflutteringbymalegivestestthat
pheromoneispresent
=bioassay(=reliabletest)

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TypesofPheromonoes
Therearedifferenttypesofpheromones.Someoftheseare
alarm,foodtrailandsexpheromones.
Alarmpheromonesareproducedbycertaininsectthatwill
actwhenattacked.Insectssuchasants,termitesandbees
willproduceacertainsmellwhentheyareattackedbya
predator.
Ininsects,thereareepideicticpheromonesthatareusedto
markterritories.Insectswilllaytheireggsoncertainfruits
tosignaltootherinsectsthattheyshouldfindotherplaces
toclutch.

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Territorialpheromonesarequitesimilartotheepideicticones.Itis
atermthatisusedtorefertopheromonesproducedtomark
boundariesbyanimalslikedogsandcats.Theseanimalsmayuse
urineasapheromonesign.
Releaserpheromonesarethemostcommonlyproduced.Theyare
secretedinordertoinfluencethebehaviorofthesamespecies.Some
insectswillproducemoleculesinordertoattractmalesthatmaybe
atadistance.Thisdistancemayvaryfromonetotwomiles,andthe
smelldoesnotusuallylastforlong.
Processingchemosignalslikepheromoneshasevolvedinall
animalphylaandthusistheoldestphylogeneticreceptivesystem
sharedbyallorganismsincludingbacteria.Ithasbeensuggestedthat
itservessurvivalbygeneratingappropriatebehavioralresponsesto
thesignalsofthreat,sexanddominancestatusamongmembersof
thesamespecies.

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Everykindofanimal,notjustsex
•Aggregationpheromones–bothsexes
attractivee.g.barkbeetles
•Nematodedauer(development)
•Mammarypheromones–rabbit
Socialinsects(ants,bees,wasps)
•Alarmpheromones
•Trailpheromonese.g.ants,termites
•Primereffectse.g.queenpheromones

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Behavioural bioassay in wind tunnel
A male turnip moth is approaching
a rubber septum with an applied
mixture of female pheromones.
The male lands and tries to mate
with the pheromone emitter.

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Philip McCabe's bee beard
200 000 bees (27 kg) are attracted by swarm lures and queen
bee pheromone on Philip’s skin!

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Human pheromones
Sexpheromonesarechemical(olfactory)
signals,pheromones,releasedbyanorganism
toattractanindividualoftheoppositesex,
encouragethemtomatewiththem,or
performsomeotherfunctioncloselyrelated
withsexualreproduction.Whilehumansare
highlydependentuponvisualcues,whenin
proximity,smellsalsoplayarole
insociosexualbehaviors.

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Aninherentdifficultyinstudying
humanpheromones istheneedfor
cleanlinessandodorlessness in
humanparticipants.
Experimentshavefocusedonthree
classes of putative human
pheromones:
1.Axillarysteroids,
2.Vaginalaliphaticacids,
3.Stimulatorsofthevomeronasal
organ.

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Axillarysteroids-areproducedby
thetestes,ovaries,apocrineglands
andadrenalglands.
Thesechemicalsarenotbiologicallyactiveuntilpuberty
whensexsteroidsinfluencetheiractivity.Theactivity
changeduringpubertysuggestthathumanscommunicate
throughodors.
Severalaxillarysteroidshavebeendescribedaspossible
human
pheromones:androstadienol,androstadienone,andro
stenone,androstenolandandrosterone.

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Androstenolistheputativefemalepheromone.
Ina1978studybyKirk-Smith,peoplewearingsurgicalmaskstreatedwith
androstenoloruntreatedwereshownpicturesofpeople,animalsandbuildings
andaskedtoratethepicturesonattractiveness.Individualswiththeirmasks
treatedwithandrostenolratedtheirphotographsasbeing"warmer"and"more
friendly“.
Thebest-knowncasestudyinvolvesthesynchronizationofmenstrual
cyclesamongwomenbasedonunconsciousodorcues,theMcClintockeffect,
namedaftertheprimaryinvestigator,MarthaMcClintock,oftheUniversityof
Chicago.Agroupofwomenwereexposedtoawhiffofperspirationfromother
women.Dependingonthetimeinthemonththesweatwascollected(before,
during,orafterovulation),therewasanassociationwiththerecipientwoman's
menstrualcycletospeeduporslowdown.
The1971studyproposedtwotypesofpheromoneinvolved:"One,produced
priortoovulation,shortenstheovariancycle;andthesecond,producedjust
atovulation,lengthensthecycle".However,recentstudiesandreviewsofthe
methodologyhavecalledthevalidityofherresultsintoquestion.
[

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Androstenoneispostulatedtobesecretedonlyby
menasanattractantforwomenandisalsothoughtto
affecttheirmoodpositively.Itseemstohavedifferent
effectsonwomen,dependingonwhereafemaleisin
hermenstrualcycle,withthehighestsensitivitytoit
duringovulation.In1983,studyparticipantsexposed
toandrostenonewereshowntoundergochangesin
skinconductance.Androstenonehasbeenfoundtobe
perceivedasmorepleasanttowomenatawoman’s
timeofovulation.Itishypothesizedthatthismaybea
wayforamaletodetectanovulatingfemalewho
wouldbemorewillingtobeinvolvedinsexual
interaction.

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Copulinisafemalepheromonethatwhenreleasedwillcausethe
testosteronelevelsinmentoincrease.Justasmalepheromones
worktoincreaseattractionandsexualappealinmen,copulinworks
thesamewayinwomen.
Furthermore,ithasbeensuggestedthatintheevolutionof
unicellularprokaryotestomulticellulareukaryotes,primordial
pheromonesignalingbetweenindividualsmayhaveevolvedto
paracrineandendocrinesignalingwithinindividualorganisms.

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