19. Sexual dimorphism and behavior I Flashcards
(14 cards)
What is the main focus of the lecture on sexually dimorphic behavior?
Understanding how sex determination leads to different behaviors in males and females
The lecture specifically examines invertebrates, particularly the fruit fly.
What physical sexual dimorphism is observed in moths (Manduca sexta)?
Male moths have feathered, elaborate antennae with more receptors for detecting female pheromones
This adaptation helps males locate females more efficiently for reproduction.
How is sex determined in Drosophila?
By X chromosome dosage; males are XY and females are XX
Unlike mammals, the Y chromosome does not determine sex in Drosophila.
What is the role of the sex lethal (Sxl) gene in Drosophila?
Sxl activates female development with two X chromosomes and remains inactive for male development with one X chromosome
It sits at the top of the sex determination cascade.
What gene is crucial for male courtship behavior in Drosophila?
Fruitless gene
This gene is regulated by the Sxl gene and controls sex-specific splicing.
List the steps involved in male courtship behavior in Drosophila.
- Orientation toward female
- Tapping female with forelegs
- Wing vibration
- Licking
- Copulation attempt
What types of neurons express the fruitless gene in male Drosophila?
- Sensory neurons (olfactory, gustatory, auditory)
- Integration neurons in brain
- Motor neurons controlling courtship song and copulation
What does the DA1 glomerulus process in the olfactory system?
Male pheromone cVA (11-cis-vaccenyl acetate)
This pheromone inhibits male-male courtship.
How can the courtship behavior of isolated male Drosophila be manipulated?
By artificially activating fruitless neurons
This triggers the complete courtship sequence.
What is the function of PC1 neurons in females?
Act as command neurons for receptivity
They receive inputs from courtship song and male pheromones.
What controls copulation movements in Drosophila?
Glutamatergic motor neurons
GABAergic neurons inhibit these movements and promote uncoupling.
What effect does the sex peptide have on female receptivity after mating?
Inhibits receptivity
It is transferred from males during mating.
Can male Drosophila learn to court without the fruitless gene?
Yes, males can learn to court even without fruitless if exposed to many females
They learn to reduce courtship toward unreceptive females.
Where are the learning centers located in Drosophila?
Mushroom bodies
Learning requires fruitless-expressing neurons in these areas.
