Crayfish Exposed to Antidepressants Are More Adventurous

While the traces of drugs found in waterways alter the crustacean’s behaviors, it may leave them more vulnerable to predation

A close up of a crayfish against a white background
While observing the crayfish, the research team saw that the crustaceans exposed to low levels of the antidepressant were more adventurous and twice more likely to pop out of their shelters and explore their surroundings. University of Florida

When human medications leach into waterways, they can affect aquatic animals. In a new study published this week in the open-access journal Ecosphere, crayfish exposed to low levels of the antidepressant citalopram, also known as Celexa, altered their behavior and became more bold and adventurous.

The tiny swimmers spent more time foraging food and less time hiding under shelters, which could leave the crayfish susceptible to predators. Over time, their vulnerability could have cascading ecological effects on their natural environments, reports Douglas Main for National Geographic.

Citalopram is a selective serotonin reuptake inhibitor (SSRI) antidepressant medication, which are the most common type of antidepressant prescribed. The drug increases levels of a mood-balancing neurotransmitter called serotonin in the brain, per National Geographic. Serotonin is present in many animals, including crayfish, reports Clare Wilson for New Scientist.

Trace amounts of pharmaceuticals end up in water systems through human waste or improper disposal, such as flushing medications down the toilet, reports Tara Yarlagadda for Inverse.

Treated wastewater still contain trace amounts of drug compounds because facilities are not fully equipped to filter and remove them. So, the contaminated water flows back into the waterways, Inverse reports. While only small amounts end up back in waterways, these small doses are enough to influence neurochemistry in the tiny brains of aquatic life.

"When you flush a toilet, that small amount of pharmaceutical will make its way wherever the rest of your wastewater goes to," study co-author A.J. Reisinger, an urban soil and water quality scientist at the University of Florida, tells Inverse.

To see how the crayfish exposed to antidepressants in a natural setting respond, Reisinger and his team placed the crustaceans inside tanks of water that mimicked a usual stream environment. Each tank contained a plexiglass shelter for the crayfish to hide under.

For two weeks, the team infused the tanks with 0.5 micrograms of citalopram per liter of water. Researchers placed chemical cues for food on one side of the tank, while the other side had odors of their crayfish buddies, Inverse reports. From there, the scientists observed the crayfish and calculated how long it took them to emerge from their shelter. A control group did not receive the antidepressant.

Compared to the control group, crustaceans exposed to low levels of the antidepressant were twice as likely to pop out of their shelters and explore their surroundings, reports Natalie Grover for the Guardian. The group exposed to the medication also spent 400 percent more time in the part of the tank with the chemical food cues, reports National Geographic.

No predators were introduced during the experiment, but in the wild, the crayfishes' bold new ways may make them easy targets for raccoons, foxes, or other predators, per National Geographic.

The ecosystem's microbial components also changed when trace levels of antidepressants were added to the water, reports the Guardian. Algae and other organic compounds flourished in the tanks laced with pharmaceuticals. Researchers suspect that because the crayfish ate more, they made more waste, which feeds the algae. It is also possible that their increased scurrying movements were stirring up sediment from the bottom of the tanks, which could affect ecosystems long term, per National Geographic. The research team is working on exploring this topic in future experiments.

Flushed medications may not cause death in animals that swim in them, but they have the potential to alter normal behaviors. One way to help eliminate substances from leaching into waterways is to dispose of medications properly.