Anxiety in invertebrates opens research avenues

June 23, 2014 by Laetitia Louis
Credit: Jean-Paul Delbecque

Fr the first time, CNRS researchers and the Université de Bordeaux have produced and observed anxiety-like behavior in crayfish, which disappears when a dose of anxiolytic is injected. This work, published in Science on June 13, 2014, shows that the neuronal mechanisms related to anxiety have been preserved throughout evolution. This analysis of ancestral behavior in a simple animal model opens up new avenues for studying the neuronal bases for this emotion.

Anxiety can be defined as a behavioral response to , consisting in lasting apprehension of future events. It prepares individuals to detect threats and anticipate them appropriately so as to increase their chances of survival. However, when stress is chronic, becomes pathological and may lead to depression.

Until now, non-pathological anxiety had only been described in humans and a few vertebrates. For the first time, it has been observed in an invertebrate. To achieve this, researchers at the Institut de Neurosciences Cognitives et Intégratives d'Aquitaine (CNRS/Université de Bordeaux) and the Institut des Maladies Neurodégénératives (CNRS/Université de Bordeaux) repeatedly exposed crayfish to an electric field for thirty minutes. They then placed the crayfish in an aquatic cross-shaped maze. Two arms of the maze were lit up (which repels the crustaceans) and two were dark-which they find reassuring.

The researchers analyzed the of the crayfish. Those made anxious tended to remain in the dark areas of the maze, by contrast to control crayfish, which explored the entire maze. This behavior is an adaptive response to a felt stress: the animal aims to minimize the risk of meeting an attacker. This emotional state wore itself out after about one hour.

Anxiety in crayfish is correlated to increased serotonin concentration in their brains. Neurotransmitter serotonin is involved in regulating many physiological processes in both invertebrates and humans. It is released when stress is experienced and regulates several responses related to anxiety, such as increasing blood glucose levels. The researchers have also highlighted that injecting an anxiolytic commonly used in humans (benzodiazepine) stops the prevention behavior in crayfish. This shows how early neural mechanisms that trigger or inhibit anxiety-like behavior appeared in the evolutionary process and that they have been well preserved over time.

This work provides researchers specializing in stress and anxiety with a unique . Crayfish have a simple nervous system whose neurons are easy to record, so they may shed light on the neuronal mechanisms at work when stress is experienced, as well as on the role of neurotransmitters such as serotonin or GABA. The team now plans to study anxiety in subject to social stress and the neuronal changes that occur when the anxiety is prolonged for several days.

Explore further: Study shows crayfish exhibit anxiety-like behavior when stressed

More information: P. Fossat, J. Bacque-Cazenave, P. De Deurwaerdere, J.-P. Delbecque, D. Cattaert. "Anxiety-like behavior in crayfish is controlled by serotonin." Science, 2014; 344 (6189): 1293 DOI: 10.1126/science.1248811

Related Stories

Study shows crayfish exhibit anxiety-like behavior when stressed

June 13, 2014
( —A team of researchers working in France has found that when stressed, crayfish tend to exhibit anxiety-like behavior. In their paper published in the journal Science, the team describes how they conducted experiments ...

First fMRI images of individual neurons

June 4, 2014
A research team from CEA NeuroSpin and the Institut de neurosciences cognitives et intégratives d'Aquitaine (CNRS/Université de Bordeaux) demonstrated the possibility to obtain functional magnetic resonance images (fMRI) ...

Stress early in life leads to adulthood anxiety and preference for 'comfort foods'

July 30, 2013
Research to be presented at the Annual Meeting of the Society for the Study of Ingestive Behavior (SSIB), the foremost society for research into all aspects of eating and drinking behavior, suggests that exposure to stress ...

Scientists find that neurological changes can happen due to social status

April 19, 2012
Researchers at Georgia State University have discovered that in one species of freshwater crustaceans, social status can affect the configuration of neural circuitry.

Stressful situations show the head and the heart don't always agree

March 27, 2014
(Medical Xpress)—The head and the heart of people who suffer from high levels of anxiety react to stressful situations differently, researchers at the University of Birmingham have found.

Recommended for you

Researchers find monkey brain structure that decides if viewed objects are new or unidentified

August 18, 2017
A team of researchers working at the University of Tokyo School of Medicine has found what they believe is the part of the monkey brain that decides if something that is being viewed is recognizable. In their paper published ...

Study of nervous system cells can help to understand degenerative diseases

August 18, 2017
The results of a new study show that many of the genes expressed by microglia differ between humans and mice, which are frequently used as animal models in research on Alzheimer's disease and other neurodegenerative disorders.

How whip-like cell appendages promote bodily fluid flow

August 18, 2017
Researchers at Nagoya University have identified a molecule that enables cell appendages called cilia to beat in a coordinated way to drive the flow of fluid around the brain; this prevents the accumulation of this fluid, ...

Researchers make surprising discovery about how neurons talk to each other

August 17, 2017
Researchers at the University of Pittsburgh have uncovered the mechanism by which neurons keep up with the demands of repeatedly sending signals to other neurons. The new findings, made in fruit flies and mice, challenge ...

Neurons involved in learning, memory preservation less stable, more flexible than once thought

August 17, 2017
The human brain has a region of cells responsible for linking sensory cues to actions and behaviors and cataloging the link as a memory. Cells that form these links have been deemed highly stable and fixed.

How we recall the past: Neuroscientists discover a brain circuit dedicated to retrieving memories

August 17, 2017
When we have a new experience, the memory of that event is stored in a neural circuit that connects several parts of the hippocampus and other brain structures. Each cluster of neurons may store different aspects of the memory, ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.