Washington (AFP)

Crayfish exposed to antidepressants from contaminated water behave more "recklessly", getting out of hiding faster and spending more time looking for food, according to a study released Tuesday.

This work, published in the journal Ecosphere, sheds light on the unintended consequences that human drugs can have on the aquatic environment.

"Our study is the first to investigate how crayfish respond to antidepressants at levels representative of those found in the streams and ponds where they live," explains Alexander "AJ" Reisinger, of the University of Florida. and one of the main authors of the study.

Antidepressants, released directly into sinks or present as traces in the urine, can end up in the environment, either because of faulty septic tanks or wastewater treatment plants not being equipped to filter them.

US officials recommend against throwing unused drugs down the toilet or sinks, and are organizing return days.

"Because they live in water, animals like crayfish are regularly exposed to small amounts of these drugs. We wanted to know how this affected them," explains the researcher.

His team looked at the impact of selective serotonin reuptake inhibitors (SSRIs), which work by increasing levels of serotonin, sometimes referred to as the "happiness hormone."

This is what is used in the antidepressant Prozac, for example.

The researchers recreated the freshwater environment of crustaceans in a laboratory.

Some were exposed to realistic antidepressant levels for two weeks, and some were not.

The crayfish were then placed facing a Y-shaped path, with a small entrance leading to two different paths.

One was sending signals for food, the other for another crayfish.

Shellfish that were exposed to antidepressants left their shelter more quickly, and spent more time looking for food.

But they avoided the other crayfish, which shows that they weren't looking for confrontation any more.

This behavior could expose them to greater risks from their predators, such as eels or turtles, or even certain mammals or birds.

"To better understand what this could cause in our waterways and rivers or for the food chain, it would require more work on the interactions between different pollutants," Alexander "AJ" Reisinger told AFP.

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