The common sand shrimp, Crangon crangon, a small shrimp endemic to the northeast Atlantic, is capable of changing color to match its surroundings. This superpower is made possible by pigments in special organs embedded in their skin called chromatophores.
The effects that antidepressants have on wildlife is a growing research topic as more people take these drugs and secrete the leftover compounds into wastewater. These compounds then find their way into water bodies, like the ocean. They are so damaging due to their effect on the neurotransmitters, molecules important for movement, present in all animals.
A pair of researchers from the UK's University of Portsmouth designed an experiment to investigate the possible interaction between antidepressants and cryptic coloration in sand shrimp. They exposed adult shrimp to varying low levels of the antidepressant fluoxetine for three time intervals (1 hour, 1 day, or 1 week). Then, they altered the color of the substrate the shrimp were in from solid white to solid black and measured how dark their bodies became as the shrimps' chrompatophores gained or lost pigment.
The results of the investigation were inconclusive. In two of the three studies the researchers saw a high degree of correlation between shrimp "darkness" and substrate color. But, there was no clear effect of fluoxetine exposure on this correlation. Although inconclusive, this investigation does draw attention to an important issue: how do the medications we take affect wildlife downstream?