Chronic exposure to environmentally-relevant concentrations of fluoxetine (Prozac) decreases survival, increases abnormal behaviors, and delays predator escape responses in guppies

• Chronic exposure to environmentally-relevant fluoxetine concentrations.
• Decreased survival, reduced growth, abnormal behaviors in exposed juveniles.
• Delayed predatory escape responses in adult guppies.
• Male and female guppies have similar responses to external fluoxetine exposure.
• Effect of and sensitivity to fluoxetine differs with age in guppies.

This study evaluates the impact of fluoxetine, an antidepressant drug and common pollutant in aquatic environments, on growth, survival, and behavior in juvenile guppies and on predator escape responses in adult guppies (Poecilia reticulata). In juveniles, the effects of acute (4d) and chronic (35d) exposure on growth and survival were examined, and behavioral changes were noted throughout the chronic experiment. In adults, escape responses to a mock predator during chronic (28d) fluoxetine exposure were videotaped to determine the overall speed of response in treated vs. control fish. The effects of fish gender and the presence of a group/school on escape responses were also determined. Our results show that acute exposure to nominal concentrations of 0.03 and 0.5 μg/L, levels within the environment, did not adversely impact juvenile guppy survival. However, chronic exposure significantly reduced weight, length, and belly width/girth measurements compared to controls. Chronic exposure also resulted in abnormal swimming behavior and reduced survival in juveniles. In adults, fluoxetine exposure significantly delayed predator escape responses in both males and females. Escape responses were also reduced when adults were tested either individually or in a group, with significantly more delayed responses seen in individually tested fish. Taken together, these findings suggest that fluoxetine can impact guppy populations, during both juvenile and adult stages, with chronic exposure resulting in decreased survival and growth and altered behavioral responses.

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