The Role of Serotonin in Aggressive Contests in the Stalk-Eyed Fly

Brenda S. Dick


The biogenic monoamine 5-HT is thought to play a key role in mediating perceptions of resource availability, social hierarchies and aggression in many vertebrate and invertebrate species. In the sexually dimorphic species Teleopsis dalmanni, males frequently engage in agonistic contests to gain access to food and mates. The exact role of 5-HT at physiological levels in mediating aggression is unknown. We staged agonistic interactions over access to food resources after a period of starvation to test for evidence of 5-HT effects on winning aggressive contests. Recorded fights were scored to determine winners and losers. HPLC-ED was used to measure 5-HT monoamine levels in the fly brain. Levels of 5-HT, measured immediately after fights, did not predict the winner of agonistic contests. This suggests that 5-HT has a modifying enhancing effect on aggression but is not required for agonistic contests.