To mate or not to mate?

The neuronal circuitry underlying male-specific courtship behaviour in flies

Mating behavior is a critical part in evolution. Animals often use colorful feathers, pretty songs, and elaborate courtship rituals to help them achieve a successful copulation.

However, the neural basis of mating behavior was unknown until the arrival of new techniques in genetics and neuroscience.

A recent study published in eLife examined the neural pathways guiding the courting ritual in male fruit flies.

Fruit flies have an elaborate courting ritual: first, a male orients towards and follows a female; then he touches her abdomen with his foreleg and, if she responds, he extends one of his wings and performs a song-like vibration with it. Finally, he licks the female’s genitalia and attempts to copulate with her.

Previous research had found that around 1500 neurons are involved in courtship behavior.

The present study investigated how these neurons are connected to achieve the above behavior.

Researchers focused on two types of neurons: M cells that respond to male pheromones (i.e. chemicals that affect the behavior of other animals and insects of the same type, for example, by attracting them sexually), and F cells that respond to female pheromones.

The experiment showed that activating the M and F cells can modify male courtship behavior.

In addition, researchers found that a cluster of neurons called P1 neurons only exit in the brain of male flies.

The P1 neurons are activated during the start of courtship behavior. When F cells are activated, P1 neurons are excited; when M cells are activated, P1 neurons are not excited and even get suppressed.

Subsequently, researchers found that M cells can activate a cluster of neurons called mAL that send out inhibitory signals.

Inactivating the mAL neurons leads to males courting each other.

Furthermore, mAL neurons form connections with P1 neurons and inhibit their activity. In this way, male-male courtship is inhibited.

To summarize, the balance between excitation and inhibition decides the male-specific courtship behavior.

Citation: Campetella F, Sachse S. (2015). To mate or not to mate. eLife. 4:e13093. doi: 10.7554/eLife.13093  
Figure legend: This image is derived from the cited article under CC-BY license.