Antidepressants make crayfish bolder, increasing risk of predation

A crayfish explores one of the artificial streams used in the experiments at the University of Florida. Photo by A.J. Reisinger/University of Florida
A crayfish explores one of the artificial streams used in the experiments at the University of Florida. Photo by A.J. Reisinger/University of Florida

June 15 (UPI) -- When exposed to antidepressants, crayfish are less inhibited, emerging more readily from hiding to hunt for food.

This bold behavior, observed in lab tests at the University of Florida, could put the freshwater crustaceans at greater risk of predation.


Though the latest experiments -- the results of which were published Tuesday in the journal Ecosphere -- were performed in the lab, it's likely crayfish in the real world are being regularly exposed to small amounts of antidepressants and other medications.

"Low levels of antidepressants are found in many water bodies," lead author A.J. Reisinger, an assistant professor of soil and water sciences at Florida, said in a press release.

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When drugs, including antidepressants, are disposed of improperly, they can end up polluting local waterways.

Additionally, people taking antidepressants excrete trace amounts of the drugs whenever they use the bathroom.

To measure how this problem might impact crayfish behavior, researchers placed crayfish in a makeshift shelter and placed the shelter at the entrance to a maze.

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Scientists exposed some of the crustaceans to antidepressants, and then opened each of the shelters.

Emerging crayfish faced two options, a lane featuring the smell of food and a lane featuring the smell of another crayfish.


Researchers found crayfish exposed to antidepressants emerged from their shelters earlier and took more time to search for food.

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However, the experiments showed the dosed crayfish were equally as wary of other crayfish as the sober crustaceans from the control group, suggesting antidepressants don't increase aggression.

The findings suggest changes in crayfish behavior could not only expose the crustaceans to predation, but also trigger other knock-on effects throughout freshwater ecosystems where they live.

"The study also found that crayfish altered levels of algae and organic matter within the artificial streams, with potential effects on energy and nutrient cycling in those ecosystems," Reisinger said.

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"It is likely that the altered crayfish behavior would lead to further impacts on stream ecosystem functions over a longer time period as crayfish continue to behave differently due to the SSRIs. This is something we'd like to explore in future studies," he said.

Authors of the new study suggest people can help protect freshwater species by making sure all unused medications are disposed of properly.

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