Trace amounts of antidepressants washing into rivers and lakes could be making crayfish behave more boldly, and disturbing their ecosystems.
Evidence has been growing that various medications can end up in waterways because they are excreted in people’s urine. This includes antidepressants known as selective serotonin reuptake inhibitors (SSRIs), which are widely used to reduce depression and anxiety, with almost one in eight people taking them in the US.
In people, SSRIs raise levels of a brain-signalling chemical called serotonin, which is present in many animals including crayfish. Lindsey Reisinger at the University of Florida and her colleagues wondered if they would make crayfish less fearful, in the same way the drugs makes humans less anxious.
Her team compared crayfish behaviour in two artificial water streams, one of which had trace levels of an SSRI antidepressant called citalopram. When the medicine was present, the animals were nearly twice as fast to emerge from their shelters to explore their surroundings and also spent nearly twice as long searching for food. “They spend less time hiding and go into a new environment more quickly,” says Reisinger.
The animals’ greater boldness could have several effects, like making them more vulnerable to predators such as fish and wading birds, says Reisinger. While some crayfish species are classed as invasive in some areas, others are endangered.
Having crayfish spending greater time searching for their food – such as algae and leaf litter – could also reduce the amount of this organic matter in streams, which could have knock-on effects on the ecosystems.
To reduce the problem, people should never dispose of unwanted pharmaceuticals into household drains, but should return them to pharmacies, says team member Alexander Reisinger, also at the University of Florida.
Journal reference: Ecosphere, DOI: 10.1002/ecs2.3527
Sign up to Wild Wild Life, a free monthly newsletter celebrating the diversity and science of animals, plants and Earth’s other weird and wonderful inhabitants
More on these topics:
Read more at New Scientist