Fluoxetine alters behavioral consistency of aggression and courtship in male Siamese fighting fish, Betta splendens.

The detrimental effects of steroid-mimics are well known but investigations on non-steroid pharmaceuticals are less common. In addition, most behavioral studies do not examine the effects at multiple time points. This study examined the effects of fluoxetine, a selective serotonin reuptake inhibitor, on behavior when male Siamese fighting fish encounter female and male dummy conspecifics simultaneously. Thus, how chemical exposure impacts behavioral consistency and whether individuals differ in their sensitivity to exposure was assessed. Overall aggression was reduced after fluoxetine administration while courtship was unaffected. Fluoxetine affected behavioral consistency towards both the male and female, with individuals behaving less consistently to the male and more consistently to the female. In addition, males appeared to differ in their sensitivity to fluoxetine exposure as not all males reduced their aggression after administration. This has important implications for studying the effects of unintended pharmaceutical exposure. Exposure may have evolutionary implications as it may influence both territorial defense and mating success. In sum, these findings demonstrate that pharmaceutical exposure may alter more than just overall level of behavior and stress the importance of examining the effects of exposure on an individual level.