Antidepressants like prozac (fluoxetine) have helped millions of people around the world, but studies show they may be harming wildlife and wild fish
Antidepressants with tongue-twisting names such as fluoxetine (Prozac), paroxetine (Paxil), fluvoxamine (Luvox), citalopram (Celexa), escitalopram (Cipralex) and sertraline (Zoloft), are typically the first choices for treatment of depression and anxiety disorders and thus, have been a godsend for many millions of people around the world.
But these psychoactive drugs, which are metabolized mainly by the liver, are not completely broken down in the human body, so they give rise to active metabolites (ref). The body then eliminates the drug itself as well as its metabolites in urine and feces. Which which raises an important question: what happens to them after they are excreted?
Disturbingly, pharmaceutical waste and metabolites end up in the water. Basically, with our improvements in analytical techniques, we’ve been detecting antidepressants almost everywhere: in wastewater, surface water, groundwater, and even drinking water. But wastewater treatment plants are not specifically designed to completely remove pharmaceutical drugs and their metabolites from water, so the residuals enter the environment through effluent or sludge, where they persist at low levels in rivers, lakes, and oceans. This spells trouble: The latest studies are finding these drugs and their metabolites are accumulating in the tissues of aquatic organisms like fish, and are dramatically altering fish behavior, life history, and reproductive traits as a result.
Despite the fact that pharmaceutical pollutants are becoming a pervasive issue in water bodies worldwide, the full impact of these chemicals on aquatic wildlife, particularly on behavior and reproductive success, is still unclear.
A new study as designed to address this information deficit. To explore the effects of prozac pollution, an international collaboration launched a five-year investigation where the researchers exposed wild-caught guppies to three environmentally relevant concentrations of fluoxetine (Prozac) over multiple generations. Male guppies were the focus of this study due to their heightened sensitivity in measurable ways to environmental changes.
After five years of fluoxetine exposure, the team tested fish behavior, physical condition, and reproductive health. What they found was concerning. The researchers measured key life-history traits (Figure 1) such as body condition, coloration, and gonopodium size (a modified anal fin used as a reproductive organ in male livebearing fishes), along with critical sperm traits including vitality, number, and velocity.
The study revealed that fluoxetine exposure disrupted the natural correlations between all key traits measured. For example, the expected link between activity levels and body condition, and between gonopodium size and sperm vitality, was altered. This disruption indicates that the fluoxetine pollution is interfering with the physiological trade-offs fish make between survival and reproduction.
“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 the study’s lead author, behavioral and evolutionary biologist Upama Aich, a postdoctoral fellow at Monash University School of Biological Sciences, where she studies the effects of pharmaceutical and agricultural pollutants on animal behavior and reproduction.
Predictably, there were measurable behavioral effects, too.
“Fluoxetine exposure also 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,” reported one of the study’s co-authors, behavioral ecologist Giovanni Polverino, an Assistant Professor at the University of Tuscia and a Adjunct Research Fellow at Monash University and the University of Western Australia. Professor Polverino studies how animals respond to environmental changes and predicts how species may respond to a rapidly changing world.
The study’s most disturbing finding was that even when exposed to low levels over a long period of time, fluoxetine and its metabolites harms male guppies. The fish were exposed to “environmentally relevant” fluoxetine levels — similar to what they would encounter in the wild.
“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,” pointed out the study’s senior author, behavioral and evolutionary ecologist Bob Wong, a Professor in the School of Biological Sciences at Monash University, and the Secretary of the International Society for Behavioral Ecology.
This study provides critical insights into how chronic exposure to common pharmaceutical pollutants and their metabolites can fundamentally alter important traits that fish — not just guppies — rely upon for survival and reproduction. But further, it’s important to note that other animals are being affected too: For example, a few years ago, I shared a disturbing study about how prozac is affecting starling behavior (you can read more about that here).
This study serves as an important warning, highlighting the critical need for a comprehensive approach to evaluating the ecological and evolutionary consequences of pharmaceutical pollution. As humans expand our population, and as our reliance on medication grows, so too does the burden we place on natural systems. As we continue to introduce new pollutants into the environment, understanding their negative effects on wildlife and acting accordingly is essential for preserving biodiversity and safeguarding the overall health of ecosystems and the services they provide.
These findings have broader implications for understanding the adaptive capacity of wildlife facing environmental challenges. In view of the profound and interconnected effects of this pollutant, especially long-term, on the behavior, life history, and reproductive traits of freshwater fish and their ecosystems, this study delivers a powerful warning and highlights the need for a comprehensive and holistic approach to assessing the ecological and evolutionary consequences of pharmaceutical pollutants in aquatic ecosystems.
Source:
Upama Aich, Giovanni Polverino, Farin Yazdan Parast, Gabriela C. Melo, Hung Tan, James Howells, Reza Nosrati, and Bob B. M. Wong (2024). Long-term effects of widespread pharmaceutical pollution on trade-offs between behavioural, life-history and reproductive traits in fish, Journal of Animal Ecology | doi:10.1111/1365-2656.14152
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