Drosophila Pheromones (unfinished)

Question 1

Courtship and mating

Answer 1

Mating is the outcome of complex series of exchanges between M and F, during which they identify one another and maybe measure fitness. Male gets close to female and vibrates wings, producing sound.

Cuticular hydrocarbons (CHCs) largely responsible. Thick and sticky hydrophobic substances, found in all anthropods. Show changes with age and temperature. Linked with protection against dessication (from evolutionary POV when insects came out of sea) (but not primary role).

Question 2

Chromatograms and Pheromone types

Answer 2

Chromatography used to separate compounds, used on fly pheromones. Compounds of different weights burned off at different times, ionisation detector gives peaks. Showed differences between M and F D.melanogaster.

Males have higher amount of 7-P and 7-T, females have more 7,11-HP and 7,11-ND)
F compounds induce male courtship, 7-T inhibits.

Question 3

Decision circuit

Answer 3

7,11-HD induced courtship involves vAB3 neurons which project to male antennal lobe and a decision by P1 projection neurons which control behaviour

Question 4

Flies without CHCs

Answer 4

Still attractive! 1/3 or courtship down to CHCs, 1/3 due to stimuli associated with being alive, 1/3 due to other stimuli.

(Got rid of all pheromones by feminizing a female.)
(Similar affects seen if you remove oenocytes where pheromones are produced)

Also showed that removal of CHCs increased inter-specific courtship (between species), suggesting that pheromones inhibit inter-specific courtship. (Done with simulans male and melanogaster female - normally don’t like one another)

Question 5

CHC detection

Answer 5

Four receptor types involved: Gustatory R, Ionotropic R, Olfactory R, Pickpocket
No single mutant abolishes courtship

Question 6

Cost of pheromone detection

Answer 6

Ability of males to detect female pheromones comes at cost. Have lower fat levels, are less resistant to starvation and die younger. Due to taste neurons on wing and feet.

Question 7

Different species, different responses to pheromones

Answer 7

Female 7-HD excites melanogaster males but inhibits simulans males. Both detect it via ppk (used CRISPR to KO ppk in both). Effect must be central.

In both, 7HD activates same pathways up to projection neuron 1. Difference lies in species-specific weighting of vAB3 and mAL inputs to P1.

Question 8

Male produced pheromones

Answer 8

Repel other males or lead to aggression, attract females.
cis-Vaccenyl acetate: Transfer from male to female during mating –> makes females less attractive to males (so that other males don’t mate).
Also, female lays eggs on food and releases it onto food, which causes females to aggregate