Australian researchers have found further evidence of the likely impact of fluoxetine, the active ingredient in anti-depressants such as Prozac, on wild fish.
A team led by Jake Martin from Monash University discovered that even low doses commonly found in the environment can affect the way wild-caught mosquitofish (Gambusia holbrooki) behave towards each other when foraging.
It also highlights, says Martin, the importance of factoring in social context when investigating the impacts of psychoactive pollutants on exposed wildlife.
More than 3700 pharmaceutical medications are now commercially available, and their environmental contamination is a growing concern.
Martin says more than 600 different drugs have been detected in the environment, even in areas “as remote as Antarctica”. Many of these are psychiatric drugs, with sedatives, hypnotics, anti-depressants and anti-anxiety drugs the most common.
Pharmaceuticals are pumped into the environment largely through wastewater, and have been found in rivers, streams, ground and surface water, soils and drinking water.
Although it’s been known since the 1960s that treatment doesn’t completely remove them, there is relatively little understanding about their impact on ecosystems.
However, drugs like fluoxetine remain biologically active and have been shown to accumulate in the tissues of wildlife, says Martin.
“Given that these drugs are specifically designed to alter mood and behaviour in humans, they also have the potential to do so in exposed wildlife,” he and his co-authors write.
“Indeed, recent findings have suggested that psychoactive drugs can alter the behaviour of aquatic wildlife at levels presently detected in the environment,” Martin notes.
But few studies have considered how social context might factor into this.
Martin and colleagues collected 445 wild female mosquitofish from a lake and gave them a month to acclimatise to life in the lab to ensure they were eating and behaving naturally.
They then exposed them to the low levels of fluoxetine commonly found in the environment, as well as higher levels found in the most contaminated sites around the world. A third group acted as a control.
After 28 days, their behaviour was tested in a foraging experiment, either individually or in groups of three, using chironomid larvae as prey.
While the drug didn’t change the behaviour of solitary fish, it reduced levels of aggressive interactions and food consumption in both group settings, with effects more pronounced in the high-dose group.