1. Courtship in Drosophila

2. The vinegar fly, drosophila melanogaster
Successful species—worldwide, in lab…reproductive rituals must be adaptive and robust.

3. Courtship is a stereotyped dance
Plus video

4. Sensory input informs progression of the ritual
Sensory input informs progression of the ritual. On the right, common metrics to measure courtship success.

5. Decisions Whom to court?
Female vs Male seems innate
Visual, olfactory cues
Receptive vs. Non-Receptive is learned
Olfactory cues
Males can save considerable energy by limiting courtship to receptive females

7. Pheromones aid male decision making
Cis-vaccenyl acetate cVA
Volatile compound
Sensed by males and females
Produced by males only
Inhibits male courtship, including song

9. Pheromone receptors
OrX=Or67d for cVA

10. sNMP is required for optimal cVA action
sNMP is required for optimal cVA action. LUSH may be the true ligand for Or67d, but requires cVA binding to alter its conformation. Experimentally altering its conformation by making a genetic substitution that mimics what happens when cVA binds results in constitutive activation of Or67d receptor complex.

11. Organization of the cVA sensing circuit
DA1 is sexually dimorphic—larger in males than females. Also the PN that synapse in DA1 have larger and distinct arborizations in the PC than female PN do.
Or47b is a receptor for an unknown pheromone, which may provide a species specific mating cue (rather than sex specific).
Convergence of pheromone signals in the PC occurs completely distinctly from fruit odors in the sexually dimorphic lateral horn.

12. Generating sexual dimorphism
Fruitless (Fru) and Doublesex (Dsx)
Fru acts in the NS
Males lacking Fru do not sing
Females expressing Fru do sing
No effect of Dsx
2000 Fru neurons in both sexes
GFP fused to Fru promoter, magenta labels synapses

13. 1996 original report of Fru

15. Neurons required for singing
FruP1 neurons in the dorsal PC (~20)
In sexual mosaics, if these cells are masculinized (express male isoform of Fru) females will generate song
Female thorax is capable of singing, but this action is never selected
Direct stimulation of thoracic ganglion generates song in headless flies of either sex
Female FlyPod song improves if her Fru+ neurons express FruM (also DsxM is required for perfect song in both sexes)
What does this remind you of? How can we interpret this headless result?

16. Return to the learning process
Virgin females of same species are the best mate
Males will be rejected by mated females
Experience determines the likelihood of subsequent mating attempts with females of a different species or the same species that has already mated

17. Candidate mechanisms Dopamine neurons
Reinforce pheromone circuits that were active during successful courtship
Or67d circuit may be a target for learning that cVA is a pheromone associated with female rejection
A set of g neurons in the PC that express FruM are necessary for the learning
Require the plasticity protein CPEB during or shortly after training

18. A gustatory receptor aids in mate selection
Gr32a expressing gustatory chemosensory neurons project directly into the ventrolateral PC. May be a site of integration with other signals—auditory, olfactory, visual. There are Fru expressing neurons in this vicinity but have not been studied on cellular level. No sex difference in Gr32a projections.
Tetsuya Miyamoto & Hubert Amrein
Nature Neuroscience 11, (2008)

19. Female Decision Accept or Reject Courtship? Male Quality cVA signal
SONG-presence and quality
Interpulse interval: provides species cue

20. Vibrations of the female antenna-left- correspond to the highest frequency of the male wing song. Matching vibration frequencies is one way for the female to pay attention to the conspecific song and block out other suitors.

21. Female Decision Mate more than once?
Female stores sperm, uses it for a while
Unless she encounters a much better quality male, she has no need to mate again
Common interest to make her unreceptive
Transfer of Sex Peptide (SP)

22. A chemical battle
SP and ovulin stimulates egg production, which helps improve the males reproductive success rate, but only SP makes the female less receptive. If a male mates with a female that already mated, he has no need to stimulate egg production, but still wants to keep her unreceptive, so he lowers the amount of ovulin released in his semen. Mechanism unknown.

23. SP suppresses mating
Females that mate with male lacking SP readily mate again
Virgins injected with SP are unreceptive
SP binds to the SPR, a GPCR that activates cAMP 2nd messenger pathway
SPR is expressed in the Fru neurons (and elsewhere)

24. Summary
Adriana Villella*, Jeffrey C. Hall2008.