Males and females of sexually reproducing animal species typically display profoundly different mating behaviours. These differences derive from the sexual dimorphism of the neural circuits, which must be encoded in the genome and established during development(1).
In Drosophila melanogaster, it is known that fruitless (fru) and doublesex (dsx) are the essential factors contributing to various aspects of sexual differentiation. The same is true for the nervous system, but it is primarily fru that regulates the sex specific courtship behaviour(2, 3).
Yu et al. genetically dissected the fru neurons of D. melanogaster into 100 distinct types. They compiled the digital 3D atlas of these neurons and computed their likely patterns of connectivity, thereby assembling them into a neural circuit that extends from sensory input to motor output(4). 11 anatomical dimorphisms were identified within the circuit: either neurons that are male specific, are more numerous in males than females, or have distinct arborization patterns in males and females.
Further investigation certainly confirmed that lacking fru in these sexually distinct neurons resulted in deficiency of specific courtship behaviour of males(5, 6). Furthermore, identifying and characterizing the neurons projecting to the sexually dimorphic neurons would clarify the process regulating male courtship behaviour in detail(7).
Continuing systematic and comprehensive searches of the neural circuit should help in unraveling the mechanism underlying the male-specific courtship behaviour.
[References]
1. Manoli DS, Fan P, Fraser EJ, & Shah NM (2013) Neural control of sexually dimorphic behaviors. Current Opinion in Neurobiology 23(3):330-338.
2. Villella A & Hall JC (1996) Courtship anomalies caused by doublesex mutations in Drosophila melanogaster. Genetics 143(1):331-344.
3. Manoli DS, et al. (2005) Male-specific fruitless specifies the neural substrates of Drosophila courtship behaviour. Nature 436(7049):395-400.
4. Yu JY, Kanai MI, Demir E, Jefferis G, & Dickson BJ (2010) Cellular Organization of the Neural Circuit that Drives Drosophila Courtship Behavior. Current Biology 20(18):1602-1614.
5. von Philipsborn AC, et al. (2014) Cellular and Behavioral Functions of fruitless Isoforms in Drosophila Courtship. Current Biology 24(3):242-251.
6. Ito H, Sato K, Kondo S, Ueda R, & Yamamoto D (2016) Fruitless Represses robot Transcription to Shape Male-Specific Neural Morphology and Behavior in Drosophila. Current Biology 26(12):1532-1542.
7. Ribeiro IMA, et al. (2018) Visual Projection Neurons Mediating Directed Courtship in Drosophila. Cell 174(3):607-+.