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Lecture 25: The Perfumes of Sex & Life

Lecture 25: The Perfumes of Sex & 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

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Lecture 25: The Perfumes of Sex & Life

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  1. Lecture 25: The Perfumes of Sex & Life CHEMICAL COMMUNICATION

  2. 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

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

  4. 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)

  5. Pheromones • Produced from exocrine glands • that’s EXO not ENDO • Produced in liquid, but can be released as • streams, droplets, thin films, aerosols • Creation of the “Active Space”

  6. 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.

  7. 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.

  8. Pheromones • Classes/Types • Sex pheromones • Trail pheromones • Alarm pheromones • Aggregation pheromones • “Social” pheromones

  9. 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.

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

  11. Vine mealybug a) native to the Mediterranean region b) spreading throughout CA vineyards

  12. a 5 4 3 VMB / vine / 2 min search b 2 1 0 “Microencapsulated” sex pheromone and mating disruption Control Sex pheromone

  13. Anagyrus pseudococci

  14. 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)

  15. 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

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

  17. 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.

  18. 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)

  19. “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

  20. “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

  21. 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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