lecture 25: the perfumes of sex & life chemical communication

Lecture 25: The Perfumes of Lecture 25: The Perfumes of Sex & LifeSex & Life

CHEMICAL COMMUNICATION

Key Points: Chemical communication

• What is the difference between semiochemicals and pheromones

• Describe two modes of action of pheromones• How can sex pheromones improve our food

quality• Name three pheromones and how they work• Define Intra specific and Interspecific• How does an HIPV work

SemiochemicalsSemiochemicals

• KAIROMONESKAIROMONES– Inter-species specificInter-species specific– Advantage to the receiverAdvantage to the receiver

• ALLOMONESALLOMONES– Inter-species specificInter-species specific– Advantage to the senderAdvantage to the sender

• PHEROMONESPHEROMONES– Intra-specificIntra-specific

PheromonesPheromones

• ““A chemical signal released to the outside A chemical signal released to the outside of the body of the producer that effects of the body of the producer that effects the the physiologyphysiology or or behaviorbehavior of a of a receiving individual of the same species.receiving individual of the same species.””

• From the Greek From the Greek phereinpherein (to carry) + (to carry) + hormonhormon (to excite) (to excite)

PheromonesPheromones

• Produced from exocrine glands Produced from exocrine glands

– thatthat’’s s EXOEXO not not ENDOENDO– Produced in liquid, but can be released asProduced in liquid, but can be released as– streams, droplets, thin films, aerosolsstreams, droplets, thin films, aerosols

• Creation of the Creation of the ““Active SpaceActive Space””

Pheromonal Active SpacePheromonal Active Space• For some insects it can be quite For some insects it can be quite largelarge

– Gypsy MothGypsy Moth– 1,800 meters (that is more than one mile)1,800 meters (that is more than one mile)

by 100 metersby 100 meters

by 50 metersby 50 meters

• And And powerfulpowerful– one GM female possesses 0.01 μg which one GM female possesses 0.01 μg which

hypothetically could incite a response in one billion hypothetically could incite a response in one billion males.males.

PheromonesPheromones

• Two Two MODES OF ACTIONMODES OF ACTION1) 1) RELEASERSRELEASERS

immediate effect on the central nervous immediate effect on the central nervous system & behavior of the receiving animal.system & behavior of the receiving animal.

2) PRIMERS2) PRIMERS

triggers a chain of physiological- triggers a chain of physiological- developmental events that may take days, developmental events that may take days, to weeks before an overt response is seen.to weeks before an overt response is seen.

PheromonesPheromones

• Classes/TypesClasses/Types– Sex pheromonesSex pheromones

– Trail pheromonesTrail pheromones

– Alarm pheromonesAlarm pheromones

– Aggregation pheromonesAggregation pheromones

– ““SocialSocial”” pheromones pheromones

Sex PheromonesSex Pheromones

• The best known & best studied of all The best known & best studied of all pheromone classes.pheromone classes.– FunctionFunction: Gender attraction: Gender attraction– Most frequently females Most frequently females ““callingcalling”” to males to males– Occasionally males Occasionally males ““callingcalling”” to females to females– Rarely, sex attractants released by both Rarely, sex attractants released by both

genders of a species.genders of a species.

Sex PheromonesSex Pheromones

• Chemistry of sex pheromones known for Chemistry of sex pheromones known for several hundred insect species.several hundred insect species.

• Uses:Uses:

– monitoringmonitoring

– controlcontrol• trap outtrap out• male confusionmale confusion

Vine mealybuga) native to the Mediterranean regionb) spreading throughout CA vineyards

“Microencapsulated” sex pheromoneand mating disruption

ControlSex pheromone

a

0

1

2

3

4

5

VM

B /

vine

/ 2

min

sea

rch

b

Anagyrus pseudococci

Trail PheromonesTrail Pheromones

• Commonly found in numerous social Commonly found in numerous social insect speciesinsect species– ants, termites & some non-social aggregating ants, termites & some non-social aggregating

caterpillars (tent caterpillars)caterpillars (tent caterpillars)– Used for orientation Used for orientation to & from the nest forto & from the nest for

the establishment of the establishment of foraging trailsforaging trails (highways)(highways)

Trail PheromonesTrail Pheromones

• VolatileVolatile– frequently added to when forage is rewardingfrequently added to when forage is rewarding– quickly dissipates when forage is reducedquickly dissipates when forage is reduced

• SourcesSources– tarsal glands - abdominal glands - venomtarsal glands - abdominal glands - venom

• Potential for control??Potential for control??– Has been tried experimentally with pest antsHas been tried experimentally with pest ants

• e.g., fire antse.g., fire ants

Alarm PheromonesAlarm Pheromones

• Common in social insects & aggregate feedersCommon in social insects & aggregate feeders– wasps, termites, bees, & some aphidswasps, termites, bees, & some aphids

• FunctionFunction– defensedefense

• recruitment of nest-matesrecruitment of nest-mates– dispersaldispersal

• aphidsaphids

• VolatileVolatile

Aggregation PheromonesAggregation Pheromones• Function:Function:

– Signal that recruits conspecifics to a food Signal that recruits conspecifics to a food source.source.

– Known in bark beetles & certain desert Known in bark beetles & certain desert grasshoppers.grasshoppers.

– Can also function in an anti-aggregation Can also function in an anti-aggregation mode when sufficient individuals are mode when sufficient individuals are present.present.

Herbivore induced plant volatile (HIPV’s)

• Produced by plants when herbivores feed on them

• Pulls in natural enemies and increases biocontrol

• i.e. winter green (methyl salicylate)

““Social PheromonesSocial Pheromones””

• Best known in the social Hymenoptera, Best known in the social Hymenoptera, most especially the honey bee.most especially the honey bee. ““Queen SubstanceQueen Substance””

• first elucidated in the 1950first elucidated in the 1950tiesties

• chemically complex (long chain fatty chemically complex (long chain fatty acids)acids)

• from the mandibular glands of a gynefrom the mandibular glands of a gyne

““Social PheromonesSocial Pheromones””

• Gynes have a dilemmaGynes have a dilemma– Must maintain their reproductive status!!Must maintain their reproductive status!!– Do this in two ways:Do this in two ways:

• suppress ovarian development by daughterssuppress ovarian development by daughters

• prevent daughters from replacing her.prevent daughters from replacing her.

– SolutionSolution• chemo-sterilizationchemo-sterilization

Key Points: Chemical communication

• What is the difference between semiochemicals and pheromones

• Describe two modes of action of pheromones• How can sex pheromones improve our food

quality• Name three pheromones and how they work• Define Intra specific and Interspecific• How does an HIPV work