Neural circuits for sexually dimorphic and sexually divergent behaviors in Caenorhabditis elegans

•Several recent advances are driving renewed interest in the C. elegans male.•Dimorphic regulation of reproductive muscles facilitates dispersion of progeny.•Biological sex ‘tunes’ shared circuits to optimize behavioral strategies.•Distributed effects of the sex-determination pathway coordinate sex-typical behavior.

Increasing interest in sex differences in Caenorhabditis elegans neurobiology is resulting from several advances, including the completion of the male tail connectome and the surprising discovery of two ‘new’ neurons in the male head. In this species, sex-specific circuits in the hermaphrodite and male control reproductive behaviors such as egg-laying and copulation, respectively. Studies of these systems are revealing interesting similarities and contrasts, particularly in the mechanisms by which nutritional status influences reproductive behaviors. Other studies have highlighted the importance of sexual modulation of shared neurons and circuits in optimizing behavioral strategies. Together, these findings indicate that C. elegans uses intertwined, distributed sex differences in circuit structure and function to implement sex-specific as well as sexually divergent, shared behaviors.