Fluoxetine Found to Disrupt Reproductive Behaviors in Fish

Long-term exposure to pharmaceutical pollutants may be dramatically altering fish behavior, impacting their ability to reproduce and survive, according to research led by scientists from Monash University and the University of Tuscia. The study was published in the Journal of Animal Ecology.

Human pollution is linked to biodiversity loss

Pharmaceutical pollutants in waterways are an increasing global concern. Antidepressants such as fluoxetine enter water bodies through wastewater discharge and can persist at low levels in rivers, lakes and oceans. Human pollution has been linked to significant biodiversity loss, with previous studies showing that environmental pollutants can affect essential animal behaviors, including activity levels, predator avoidance and reproduction.

Despite the urgency of the issue, the impact of pharmaceutical pollutants on aquatic wildlife remains poorly understood.

Fluoxetine alters key reproductive traits

The study tracked wild-caught male guppies over five years, exposing them to three environmentally relevant concentrations of fluoxetine across multiple generations.

“The low- and high-fluoxetine treatments reflect concentrations repeatedly detected in freshwater habitats – with the low representing common surface water concentrations in fluoxetine-contaminated systems and the high representing levels typically found in heavily effluent-dominated waterbodies,” said Dr. Upama Aich, lead author and postdoctoral research fellow at Monash University.

Several characteristics were measured throughout the experiment to assess any changes in behavior or health, including body condition, coloration, gonopodium size – a modified anal fin used as a reproductive organ in males – as well as risk-taking behaviors, sperm vitality and number.

“Even at low concentrations, fluoxetine altered the guppies’ body condition and increased the size of their gonopodium, while simultaneously reducing sperm velocity – an essential factor for reproductive success,” said Aich.

“Fluoxetine exposure significantly reduced the behavioral plasticity of guppies, leading to a lower capacity of the individuals to adjust their own activity and risk-taking behaviors across contexts,” said co-author Dr. Giovanni Polverino, an assistant professor at the University of Tuscia.

Fluoxetine exposure also disrupted the natural trade-offs fish make between survival and reproduction traits, for example, the expected link between gonopodium size and sperm vitality.

“This result reveals that the consequences of pollutants are broader than previously known, with fluoxetine altering the way in which individuals allocate their energy in maintaining reproductive traits to adapt to the polluted environments,” said Aich.

Does behavioral plasticity impact fishes’ ability to survive or reproduce?

“The disruption of behavioral plasticity and the altered correlations between critical traits could undermine fish populations’ ability to adapt to environmental challenges, threatening their long-term survival,” said corresponding author Dr. Bob Wong, professor and head of the Behavioral Ecology Research Group at Monash University.

However, further research is needed to understand how the impact of fluoxetine is affecting fish populations’ ability to survive and reproduce.

“Behavioral tactics that are more consistent over time may improve male efficiency in mating success, especially when their sperm quality is compromised. We need future studies to directly test whether behavioral plasticity affect fish survivability or reproduction,” said Aich.

“While our study focuses on wildlife, the presence of these contaminants in waterways is also concerning for human health. Although the concentrations in drinking water are generally low, the persistent nature of these chemicals raises questions about long-term exposure and cumulative effects,” added Aich.

Reference: Aich U, Polverino G, Yazdan Parast F, et al. Long-term effects of widespread pharmaceutical pollution on trade-offs between behavioural, life-history and reproductive traits in fish. J Anim Ecol. 2024. doi: 10.1111/1365-2656.14152

About the interviewee:

Dr. Upama Aich is a postdoctoral research fellow at Monash University, where she studies the effect of pharmaceutical and agricultural pollutants on animal behavior and reproduction. Aich holds a bachelor's degree in Zoology from the University of Dhaka and completed her PhD, in Ecology and Evolutionary Biology, from the Australian National University in 2021.