Ellen Phiddian
Cosmos science journalist
Guppies exposed to antidepressants over a 5-year period grow up with huge changes in their behaviour and reproduction, according to results from a lengthy study by Australian and Italian researchers.
The researchers say their findings, published in the Journal of Animal Ecology, have serious implications for pharmaceutical contamination in waterways.
Medicines have become common pollutants, getting into the environment via wastewater and disposal.
This has spurred researchers to study the effects of these drugs in the environment.
“Other pharmaceuticals that people use, for example paracetamol, can also have their own effects,” Dr Upama Aich, a behavioural evolutionary biologist from Monash University, tells Cosmos.
Aich and colleagues examined the effect of a highly prescribed antidepressant – fluoxetine, or Prozac – on male guppies.
Fluoxetine is a type of selective serotonin reuptake inhibitor (SSRI), which is designed to interact with proteins in human brain cells.
“Fish and humans don’t look alike, but they do have a similar nervous system pathway, even though [fishes’ are] simpler. That means antidepressants can affect all those pathways and interrupt the regulations in their bodies,” says Aich.
The researchers caught 3,600 guppies (Poecilia reticulata) from Alligator Creek in Townsville, where they are an invasive species.
These guppies were divided into 12 groups of 300 and housed in large tanks in a lab. The tanks were designed to simulate guppy habitat, with rocks, plants, and lights cycling from day to night.
After 5 months of acclimatisation, 8 of the tanks were exposed to two different levels of fluoxetine (about 30 nanograms per litre in 4 tanks and 300 nanograms per litre in 4 tanks), while the remaining 4 tanks remained fluoxetine-free as a control.
“30 nanograms per litre is a concentration that is often found in our freshwater bodies, in the surface water system,” says Aich.
“The high concentration [300 ng/l] represents the levels that are typically found in heavily effluent-dominated water bodies.”
The researchers monitored the guppies and their exposure for 5 years.
“That is a lengthy amount of time,” says Aich. “Not all ecotoxicological studies take such a long-term exposure period, because that can be quite costly.”
Both concentrations of fluoxetine altered guppy behaviour and reproduction.
“Their behaviour, their morphological traits, and their reproductive traits have been affected,” says Aich.
“We also found that not only those traits themselves, but the relationship between those traits were affected.
“For example, in animal life history, people often assume that if a fish has a higher body condition, it might have more babies. We saw that exposure to fluoxetine can affect similar relationships.”
Both the amount of fluoxetine, and the time spent exposed to it, had big influences over the guppies.
Aich says that some of their findings reflect other research done on pharmaceuticals and other aquatic creatures.
“When fish were exposed to fluoxetine, they had reduced activity and they were hiding more in their compartments – this is something that has been similar in other studies,” she says.
But the 5-year exposure period allowed them to find new effects too.
“Behavioural plasticity – this result has changed since we tested the fish when they were under 2 years exposure to the drug, compared to 5 years. So we can see how the fish are adjusting while they are under a pollution-involved environment,” says Aich.
Aich emphasises that antidepressants are extremely important for human health.
“They have helped millions of people worldwide. So it’s not our goal to take antidepressants off our shelves … but to raise the public awareness that we also have the burden to understand how those drugs can have unintended consequences for our wildlife.”
Aich cites a recent commentary written by colleagues of hers, published in Nature Sustainability, on how pharmaceuticals’ environmental impacts might be better managed.
While the commentary states that pharmaceuticals are “indispensable” to healthcare, it also highlights an “urgent need for designing greener drugs”.
“By greener drugs, they mean drugs that can be easily dissolvable,” says Aich. Newer, biodegradable, pharmaceuticals would not cause this serious pollution.
“They have also discussed how we need to have more informed and sustainable practice in prescribing these sort of drugs, and then how these drugs can be discarded in a more sustainable manner,” says Aich.
This might include pharmacy return schemes for unused prescriptions, rather than throwing them in the bin. Improved wastewater treatment could also prevent the entry of drugs into waterways.
Aich says that more research is needed to understand the full effect of these medications in the environment.
“This is the first time we have looked at behavioural plasticity, and other nuanced traits that might not be super obvious. That also means that the drugs can have their effects in a more extensive manner compared to what we previously realised,” she says.
This might include inter-species interactions in the environment.
“We need public awareness, because researchers can only do so little,” says Aich.
“We all want to work from our own place to have a better ecosystem.”
