No effect of a widespread pharmaceutical pollutant on behavior, physiology, or morphology in guppies

Pharmaceutical pollution is a global environmental threat, with antidepressants contributing a substantial proportion of pharmaceutical contaminant detections worldwide. The antidepressant fluoxetine is commonly detected in aquatic environments and has been reported to impact ecologically important behavioral and physiological traits in exposed wildlife. However, relatively few studies have examined possible effects of fluoxetine on both behavior and metabolic rate, particularly over ecologically relevant exposure timescales. Accordingly, we investigated the impacts of long-term fluoxetine exposure on foraging and antipredator behavior, metabolic rate, and morphology in female guppies (Poecilia reticulata). Fish were exposed to 1 of 3 treatments-an unexposed control (0 ng L^-1), or low or high fluoxetine (mean measured concentrations: 30 ng L^-1 and 292 ng L^-1, respectively)-for 8 mo in a semi-natural mesocosm system, corresponding to ∼2 to 3 overlapping generations. Following exposure, we quantified foraging and antipredator behavior in the presence or absence of a live predator, the spangled perch (Leiopotherapon unicolor). We then measured the rate of oxygen consumption ( $\dot{V}$ O₂) of the guppies as a proxy for standard metabolic rate, and recorded mass, standard length, and body condition as morphological measurements. Our results show that long-term fluoxetine exposure did not significantly affect the behavior, metabolic rate, or morphology of female guppies. Considered alongside previous work, our findings emphasize the importance of exposure duration in mediating the impacts of fluoxetine on fitness-related traits, with continued research being essential in identifying potential mechanisms that underpin these findings.