Meeting Abstract
P2.111 Sunday, Jan. 5 15:30 David vs. Goliath: Serotonin affects aggressive behaviors but not contest outcome of smaller competitors RIEGER, NS*; BUBAK, AN; RENNER, KJ; SWALLOW, JG; Univ. of Colorado-Denver; Univ. of Colorado-Denver; Univ of South Dakota; Univ. of Colorado-Denver nrieger@wisc.edu
In aggressive encounters, size discrepancy between competitors is often a primary determining factor of contest outcome, usually resulting in the smaller competitor conceding to its larger rival. Because winning contests can lead to significant fitness advantages, understanding the mechanisms that alter aggression is of great importance. The stalk-eyed fly, Teleopsis dalmanii, aggressively defends food resources and roosting sites daily, with a high probability of males winning a contests when faced with a smaller rival (> 5% difference in eye span). Serotonin (5-HT) has been implicated in the escalation of aggressive behaviors in both invertebrates and vertebrates. Studies in our lab have demonstrated an increased probability of winning size-matched contests as well as increasing willingness to engage in high-intensity behaviors by pharmacologically elevating neural 5-HT in this species. We hypothesized that smaller flies with pharmacologically-increased brain 5-HT in a size-mismatched contest would show more aggressive behaviors and a greater win percentage compared to non-treated counterparts. To test this, size-mismatched males were placed in a 10-minute forced fight paradigm where the smaller fly was either treated or untreated with the 5-HT precursor, 5-hydroxytryptophan, and aggressive behaviors were scored. Although probability of winning was not significantly altered by the treatment, aggressive behaviors including contest initiation, total interactions, and high-intensity behaviors were significantly higher in treated animals (p<0.008). This data suggests 5-HT plays a role in the willingness to engage and escalate aggressive behaviors warranting future studies investigating the role of 5-HT in rival assessment in stalk-eyed flies.
