Common prescription drugs and medicines have been detected in waters at levels that threaten aquatic ecosystems worldwide. New research has found that Siamese fighting fish exposed to fluoxetine, or Prozac, become timid a weak, minimizing their chances for survival
"There has been growing concern over the past two decades regarding the prevalence of pharmaceuticals and personal care products in waterways worldwide," lead author Teresa Dzieweczynski of the University of New England and her colleagues Brennah Campbell and Jessica Kane wrote.
The problem is that pharmaceuticals and personal care products (PPCPs), including fluoxetine, "are still in their active form when they enter sewage treatment systems, where they have limited removal because of their water solubility and resistance to biodegradation."
However, common drugs and PPCPs can enter the environment quite innocently, such as when a person on Prozac or certain other drugs goes to the bathroom and flushes. And as the scientists noted, sewage treatment systems cannot always detect the contaminants in our waste, due to the chemical nature of many drugs.
Fluoxetine is common in some rivers where Siamese fighting fish (Betta splendens) live. They are a small, colorful carnivorous species of fish native to the Mekong River, which runs through a number of countries in Southeast Asia.
To learn more about how the drug can affect Siamese fighting fish, researchers compared the behavior of fish exposed to various amounts of fluoxetine to those that had no exposure to the drug.
The scientists wrote that "males exposed to fluoxetine were less bold and less consistent in their behavioral responses, and the correlations between boldness over time and across assays were weaker than those for unexposed males."
Prozac is used to treat human psychiatric disorders such as depression and post-traumatic stress disorder. It is believed that the drug increases levels of the neurotransmitter serotonin, which is involved in the control of pain perception, the sleep-wake cycle and mood. An increase of serotonin in the synapse between nerves would therefore reduce reabsorption into nerve cells to relieve symptoms.
However, for Siamese fighting fish, the drug-induced timidity greatly reduces their chances for survival, as it reduces their boldness and fitness. As a result, shy fish are less likely to forage, avoid predators or attract mates.
Surprisingly, the effects of fluoxetine exposure lasted even after the drug was removed from the environment in which the fish were swimming. Therefore, researchers note that further study is required to better understand the chronic side effects of the drug and to better protect both wildlife exposed to it and people who are taking it.
Their study was recently published in the Journal of Experimental Biology.
