“Bold” crayfish excitedly scamper due to the side effects of antidepressants.

Brianne Lehan/University of Florida
Down the Drain

Flushed antidepressants make this animal unusually "bold,” scientists discover

Scientists discover that flushed anti-depressants can alter the behavior of crayfish. We should try to safely dispose of medication , researchers say.

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At a University of Florida lab, crayfish are going wild.

In a video published by University of Florida-led researchers, the small crustacean boldly scampers around a plexiglass chamber, searching for food through frenzied movements that could rival a college dance party.

But while it may look like these crayfish are merely having a good time, their bold behavior isn’t natural, according to research published Tuesday in the journal Ecosphere.

Instead, it’s been enhanced by a surprising human substance: the anti-depressant citalopram, which makes its way from human households to the watery homes of aquatic animals — like the crayfish.

Crayfish boldly move about in a lab at the University of Florida. Their behavior has been enhanced by the presence of antidepressants in their water supply.

Brianne Lehan/University of Florida

What’s new — Researchers exposed crayfish to modest doses of the antidepressant citalopram (brand name: Celexa) through their water supply, replicating drugs that have been unintentionally introduced into other waterways.

“We wanted to see if crayfish that were exposed to environmentally realistic concentrations of citalopram would show any change in their behavior,” AJ Reisinger, an assistant professor at the University of Florida who is a co-author on the study, tells Inverse.

Citalopram is a type of anti-depressant known as a selective serotonin reuptake inhibitor (SSRI), which “alters serotonin pathways in the brain” according to Reisinger. By increasing serotonin in your brain, citalopram improves mental well-being. Yet, citalopram was never intended for non-human consumption.

The researchers wanted to better understand the non-lethal side effects of anti-depressants like citalopram on the behavior of crayfish, given that SSRIs are one of the most widely prescribed class of drugs.

The researchers found that the anti-depressant had a significant impact on the animal’s behavior. Crayfish that had been exposed to citalopram were noticeably bolder, spending more time foraging for food and less time seeking the company of their fellow crustaceans.

“Our findings demonstrate the potential for the antidepressant, citalopram, to alter the behavior of crayfish, an important component of aquatic ecosystems,” Reisinger says.

This figure shows how our home water connects to larger freshwater bodies. Medication flushed down the toilet can enter into the freshwater supply, disturbing aquatic ecosystems.


Some background — Previous studies have reported on the unintended side effects of human substances on animals in waterways, from cocaine harming endangered eels to anti-anxiety medication that turns European perch fish into antisocial aggressors.

These drugs find their way from our homes to other water systems via the drain pipes in our homes, according to Reisinger. Humans secrete trace amounts of these medications through our waste — our poop and urine. But with certain widely-prescribed drugs, that can make a big difference.

“When you flush a toilet, that small amount of pharmaceutical will make its way wherever the rest of your wastewater goes to,” Reisinger says.

In the U.S., that wastewater typically leads to a septic field or wastewater treatment facility. But treatment facilities aren’t equipped to fully remove the pharmaceutical compounds, thereby draining the anti-depressant-laced water into our nation’s waterways. There are also problems with aging infrastructure leaking some of the water before it has the chance to get to a treatment facility.

The problem gets compounded even further when humans directly flush their medications down the toilet. “You should never flush unwanted medication down a drain,” Reisinger says.

A figure from the study showing the plexiglass chamber where the crayfish were exposed to antidepressants.

Reisinger et all

How they did it — The researchers placed crayfish in a shelter in a plexiglass chamber with water containing modest – 0.5 micrograms per liter — of citalopram.

One end of the chamber contained chemical cues for food and another end contained odors of their fellow crustaceans. The researchers calculated how long it took crayfish to peek their heads and completely emerge from the shelter.

They found that crayfish exposed to citalopram emerged from their shelter more quickly and spent more time foraging for food than crayfish in the control group.

Researchers also tested for changes in the nutrient composition of the water, which may have been altered by the crayfish behavior.

Finally, the scientists used a statistical model to fully test the effects of the controlled substance on crayfish, clarifying how their behavior differed from their peers that hadn’t been exposed to anti-depressants.

“You should never flush unwanted medication down a drain.”

Why it matters — The researchers’ findings show that our — often careless — disposal of medications is changing the behavior of animals like crayfish, possibly altering the aquatic ecosystem at large.

When crayfish spend more time foraging for food, they become more vulnerable to predation by larger aquatic animals. The crayfish’s more bold food-seeking behavior could also change their feeding habits, altering their ecosystem in another way.

The researchers write: “Therefore, crayfish exposed to SSRIs in the environment may be more vulnerable to predation.”

Crayfish, which Reisinger callsimportant components of aquatic ecosystems,” could alter their ecosystems’ food webs when exposed to flushed anti-depressants.

Flushed medications might not always kill animals, but they can have a host of other alarming non-lethal side effects, as these findings show. By learning how these substances affect aquatic animals, scientists can understand how manmade chemicals are altering freshwater ecosystems.

Flushed anti-depressants can alter the behavior of quatic animals — like the crayfish — and change ecosystems. You can help by safely disposing of your medication.

University of Florida

How you can help — While we can’t do much about the pharmaceuticals we excrete through our poop, we can do one thing to minimize harm to crayfish and the rest of the aquatic ecosystem: properly dispose of our medications.

Reisinger and colleagues at the University of Florida put together a helpful infographic with information on how to get rid of excess or leftover medication. Here’s the breakdown in five easy steps:

  1. Never flush your medication down the drain.
  2. Instead, remove the medication from its container.
  3. Mix the medication with coffee grounds, kitty litter, or a similar material that will be thrown out.
  4. Place the mixture in a sealed bag.
  5. Dispose of the bag in your trash can, along with your prescription container (after removing the label with your personal information).

You may also leave your medications at safe drop-off sites in your area, including:

With these steps, we can spare our aquatic friends from the aggressive side effects of human pharmaceuticals and prevent the pollution of Earth’s most vital waterways.

“Ensuring that all pharmaceuticals are used as prescribed and that any unwanted medications are properly disposed of will help to reduce our impacts on aquatic ecosystems,” Reisinger says.

Abstract: Pharmaceuticals are ubiquitous in aquatic environments, yet little is known regarding their impacts on ecological processes. Selective serotonin reuptake inhibitors (SSRIs) are frequently prescribed human antidepressants and have been shown to alter crayfish behavior. These behavioral alterations are particularly relevant as crayfish play a central role in freshwater ecosystems and often reach high biomass in anthropogenically influenced environments commonly exposed to pharmaceutical contamination. Using a 14-d artificial stream experiment, we exposed spiny cheek crayfish (Faxonius limosus) to citalopram, a common SSRI, at an environmentally realistic concentration (0.5 μg/L). We used a Y shape flume to quantify the effects of SSRI exposure on crayfish behavior and food/conspecific preference. We also tested the interacting effects of citalopram and crayfish on habitat-specific and wholestream ecosystem functions and biomass. Crayfish exposed to SSRIs exhibited increased boldness (time to emerge from shelters; P < 0.05) and spent more time orienting to food resources than nonexposed crayfish. Crayfish increased water column chlorophyll a (P < 0.01) and benthic organic matter (P = 0.03). Furthermore, crayfish potentially increased water column respiration (P = 0.09) and potentially decreased nitrate uptake (P = 0.05). SSRI exposure exhibited a potential effect of decreasing benthic chlorophyll a (P = 0.07), but there were no significant CRAY+SSRI interactions. Neither crayfish nor SSRI treatments affected whole-stream metabolism. These results suggest that citalopram has the potential to affect algal biomass but did not affect ecosystem functioning. However, alterations to crayfish behavior driven by SSRI exposure could lead to subsequent ecosystem-level effects as crayfish did affect various response metrics. We were unable to detect the effects of altered crayfish behavior at the ecosystem scale during our study, likely due to the short time frame (2 weeks) of our experiment. Further work is needed to quantify longer-term ecosystem consequences of sublethal effects of pharmaceuticals, but these results show that ecological responses to pharmaceuticals should consider the entire ecosystem.

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