The Involvement of Sonic Hedgehog and Oxytocin in the Development of Monogamous Behavior

The convict cichlid is a species of fish that exhibits monogamous behavior. The cause of this behavior can be explained by examining the development of the convict cichlid brain in comparison to that of the polygamous zebrafish. Signaling molecules known as morphogens have been identified as critical players in the development and differentitation of the forebrain. A protein called Sonic Hedgehog - encoded by the SHH gene - is a morphogen that directs the development of the ventral forebrain, including the hypothalamus (where the neurotransmitter oxytocin is produced). Evidence shows that monogamous behavior is influenced by oxytocin, with monogamous organisms having higher concentrations of oxytocin receptors in the ventral forebrain compared to their polygamous counterparts. We hypothesize that, compared to the polygamous zebrafish, the monogamous convict cichlid has an increase in expression of the SHH gene during development of the ventral forebrain, which causes an increase in expression of the oxytocin receptor gene in this region.