Crayfish Get Anxious Too!

In Brief:

Many of us experience anxiety -– the dread of taking a test you have not studied for or presenting in front of a room of people. Pressure builds, your heart sinks, and you feel weighed down. Typically, this emotion is associated with complex creatures like humans and occurs in reaction to stressful situations. However, research shows that a variety of primitive organisms, like the crayfish, can also experience anxiety.

Dr. Daniel Cattaert, a scientist at the National Center for Scientific Research in Talence, France, has studied the brains of these freshwater crustaceans. In order to test their anxiety levels, Cattaert placed crayfish in a cross-like maze where two of the rows were brightly lit and the others were pitch black. He then sent an electric current through the maze to trigger a behavioral response from the crayfish that would indicate their level of stress. Anxious crayfish stayed in the dark areas of the maze where they were more comfortable, while the non-anxious crayfish explored the lighter areas. Similar to humans trying to calm themselves down, the crayfish sought comfort during a stressful time and retreated to the darker areas.

Anxious crayfish, indicated by a higher level of glucose in the blood, tend to retreat to darker areas of the maze while their less stressed counterparts tend to explore lighter areas.

To look at anxiety on a biological level, Dr. Cattaert also measured the amount of glucose, a simple sugar, present in the crayfishes’ blood. With this method, a greater amount of glucose would indicate a higher level of anxiety. His findings showed that the stressed crayfish did indeed have a higher level of glucose in their blood than their non-stressed counterparts.

Dr. Cattaert explains that this anxious behavior originated in an ancestor common to humans and crayfish, stating that the results “suggest the conservation of several underlying mechanisms during evolution.” However, humans and crayfish have developed different ways of exhibiting anxiety. Unlike humans, crayfish are not conscious of themselves and their feelings.

So next time you break out in a nervous sweat, think of the crayfish. According to Dr. Cattaert’s research, these seemingly simple creatures can respond to stress in a way similar to humans. Although we certainly do not look alike, our freshwater friends may not be so different from us after all.

Works Cited

  1. David Tenenbaum, “Anxious crayfish, anxious people: Surprising similarities,” TheWhyFiles, June 12, 2014, .
  2. Steve Connor, “Anxiety research: Even crayfish get stressed, scientists show,” Independent UK, June 12 2014,

Image Credits:
Feature Image: cSw Staff Illustrator Wendy Wu
Story Image: cSw Staff Illustrator Sreya Das

Chief Editor: Aparna Ragupathi
Creative Team Coordinator: Sreya Das
Team Editor: Aparna Ragupathi
Team Graphic Designer: Sreya Das

This article was written by Franchesca Inay. As always, before leaving a response to this article please view our Rules of Conduct. Thanks! -cSw Editorial Staff