Lecture 25: The Perfumes of Sex

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Lecture 25 The Perfumes of Sex Life
CHEMICAL COMMUNICATION
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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

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Semiochemicals

• KAIROMONES
• Inter-species specific
• Advantage to the receiver
• ALLOMONES
• Inter-species specific
• Advantage to the sender
• PHEROMONES
• Intra-specific

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Pheromones

• A chemical signal released to the outside of the
  body of the producer that effects the physiology
  or behavior of a receiving individual of the same
  species.
• From the Greek pherein (to carry) hormon (to
  excite)

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Pheromones

• Produced from exocrine glands
• thats EXO not ENDO
• Produced in liquid, but can be released as
• streams, droplets, thin films, aerosols
• Creation of the Active Space

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Pheromonal Active Space

• For some insects it can be quite large
• Gypsy Moth
• 1,800 meters (that is more than one mile)
• by 100 meters
• by 50 meters
• And powerful
• one GM female possesses 0.01 µg which
  hypothetically could incite a response in one
  billion males.

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Pheromones

• Two MODES OF ACTION
• 1) RELEASERS
• immediate effect on the central nervous
  system behavior of the receiving animal.
• 2) PRIMERS
• triggers a chain of physiological-
  developmental events that may take days, to
  weeks before an overt response is seen.

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Pheromones

• Classes/Types
• Sex pheromones
• Trail pheromones
• Alarm pheromones
• Aggregation pheromones
• Social pheromones

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Sex Pheromones

• The best known best studied of all pheromone
  classes.
• Function Gender attraction
• Most frequently females calling to males
• Occasionally males calling to females
• Rarely, sex attractants released by both genders
  of a species.

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Sex Pheromones

• Chemistry of sex pheromones known for several
  hundred insect species.
• Uses
• monitoring
• control
• trap out
• male confusion

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Vine mealybug a) native to the Mediterranean
region b) spreading throughout CA vineyards
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Microencapsulated sex pheromone and mating
disruption
Control Sex pheromone
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Anagyrus pseudococci
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Trail Pheromones

• Commonly found in numerous social insect species
• ants, termites some non-social aggregating
  caterpillars (tent caterpillars)
• Used for orientation to from the nest for the
  establishment of foraging trails (highways)

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Trail Pheromones

• Volatile
• frequently added to when forage is rewarding
• quickly dissipates when forage is reduced
• Sources
• tarsal glands - abdominal glands - venom
• Potential for control??
• Has been tried experimentally with pest ants
• e.g., fire ants

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Alarm Pheromones

• Common in social insects aggregate feeders
• wasps, termites, bees, some aphids
• Function
• defense
• recruitment of nest-mates
• dispersal
• aphids
• Volatile

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Aggregation Pheromones

• Function
• Signal that recruits conspecifics to a food
  source.
• Known in bark beetles certain desert
  grasshoppers.
• Can also function in an anti-aggregation mode
  when sufficient individuals are present.

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Herbivore induced plant volatile (HIPVs)

• Produced by plants when herbivores feed on them
• Pulls in natural enemies and increases biocontrol
• i.e. winter green (methyl salicylate)

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Social Pheromones

• Best known in the social Hymenoptera, most
  especially the honey bee.
• Queen Substance
• first elucidated in the 1950ties
• chemically complex (long chain fatty acids)
• from the mandibular glands of a gyne

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Social Pheromones

• Gynes have a dilemma
• Must maintain their reproductive status!!
• Do this in two ways
• suppress ovarian development by daughters
• prevent daughters from replacing her.
• Solution
• chemo-sterilization

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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