Anxiety research: Even crayfish get stressed, scientists show

 

Science Editor

Anxiety is not only felt by the followers of the England football team, it can also be found in the lowly crayfish, a small lobster-like creature that appears to be capable of fearing the future just like a soccer fan, a study has found.

For the first time scientists have found unequivocal signs that the state of anxiety normally associated with higher forms of life such as humans, mammals and other animals with a backbone is also shared with a spineless species with a worrying disposition.

An experiment has shown that the freshwater crayfish can be induced into a state of deep anxiety that can only be alleviated by the same kind of tranquilisers used to treat people afflicted by a similar condition, scientists said.

The study revealed that the crayfish emotion is governed by the same chemical transmitters in its nervous system that are involved in controlling anxiety in humans, which is why anxious crayfish respond to benzodiazepine, a tranquiliser used to treat anxiety in people, scientists said

“Anxiety is different from fear, which is something that even the simplest animals show. Anxiety is a kind of fear of the fear, and animals who experience it will display adaptive behaviour to minimise the threat,” said Daniel Cattaert, a neuroscientist at the University of Bordeaux in France.

“Acute anxiety can be beneficial. After an animal has faced a bad experience then if it adapts its behaviour to minimise the risk in the future, then this can be beneficial for the animal. People thought this only occurs in animals with complex nervous systems, but we have found it in crayfish,” Dr Cattaert said.

The study, published in the journal Science, involved subjecting crayfish to a series of mild electric shocks which understandably made them nervous and so prone to flicking their tails as an escape response.

They also changed their behaviour when compared to crayfish that had not been treated with electric shocks. Instead of exploring the well-lit parts of their tank, the anxious crayfish kept almost entirely to the darker corners as light made them fearful.

“This adaptation in the stressed crayfish lasts for about an hour after being subjected to about 20 minutes of stress. A naïve crayfish will readily explore the well-lit arms of the cross-shaped tank but the stressed crayfish are clearly anxious about doing this,” Dr Cattaert said.

“There is clear decision making involved. They may start to enter the lit areas of the tank but then they stop and go back to the dark areas,” he said.

When the stressed crayfish were treated with chlordiazepoxide, a potent benzodiazepine, they overcame their anxiety and readily explored the well-lit areas of the tank, showing no abnormal aversion to light, he added.

Injecting the neurotransmitter serotonin into unstressed crayfish, however, caused them to behave as if they had undergone the electric-shock treatment. Serotonin also plays a key role in governing the stress response in humans, suggesting that there is a common origin of anxiety in crayfish and people, the researchers said.

“Our results demonstrate that crayfish exhibit a form of anxiety similar to that described in vertebrates, suggesting the conservation of several underlying mechanisms during evolution,” they said in the study published in Science.

Dr Cattaert did not want to go as far as to suggest that crayfish are showing some kind of conscious behaviour, or even that they feel pain in the same way that mammals feel pain.

“It doesn’t mean that the emotions are the same, although we have found that the mechanism that has been developed in vertebrates [animals with backbones] is also present in crayfish. But I wouldn’t say that this changes totally our view of crayfish,” he said.

“Crayfish forget things pretty rapidly and if you don’t have a long memory you have no sense of consciousness.”

Animal emotions: Do beasts feel burdened?

Emotions are seen as  something unique to humans. However, we can often see “emotions” in other animals, although not all scientists agree on whether they are exactly analogous to what people feel.

Fear An aversion to an  imminent threat is almost  universal in the animal kingdom. Rodents have been shown to fear the smell of  a predator, such as cat’s  urine, and birds in a nest  will lie low when the  silhouette of a hawk flies overhead.

Love Bonding and attachment are also both universal, but love is a subjective state. Some animals, such as swans, will form long-term mating bonds that last for much of their lives.

Sadness Any dog owner will attest to the ability of a pet  to show signs of depression  or sadness. Some wild  animals, such as elephants and chimpanzees, have been shown to mourn their dead.

Happiness Social mammals are particularly good at  displays of affection  and “happiness”. Young wolves, which live in a  pack, will clearly show  signs of being content  and “happy”.

Start your day with The Independent, sign up for daily news emails
ebooks
ebooksA special investigation by Andy McSmith
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Recruitment Genius: Electricians

£35000 - £45000 per annum: Recruitment Genius: Fully qualified electricians re...

Ashdown Group: Junior Business Systems Analyst - High Wycombe - £30,000

£25000 - £30000 per annum: Ashdown Group: Junior Business Systems Analyst role...

Recruitment Genius: Operations / Transport & Logistics Assistant

£16000 - £22000 per annum: Recruitment Genius: This highly regarded industry l...

Recruitment Genius: Finance Team Leader

£23000 - £27000 per annum: Recruitment Genius: Do you want to work for a Compa...

Day In a Page

HIV pill: Scientists hail discovery of 'game-changer' that cuts the risk of infection among gay men by 86%

Scientists hail daily pill that protects against HIV infection

Breakthrough in battle against global scourge – but will the NHS pay for it?
How we must adjust our lifestyles to nature: Welcome to the 'Anthropocene', the human epoch

Time to play God

Welcome to the 'Anthropocene', the human epoch where we may need to redefine nature itself
MacGyver returns, but with a difference: Handyman hero of classic 1980s TV series to be recast as a woman

MacGyver returns, but with a difference

Handyman hero of classic 1980s TV series to be recast as a woman
Tunnel renaissance: Why cities are hiding roads down in the ground

Tunnel renaissance

Why cities are hiding roads underground
'Backstreet Boys - Show 'Em What You're Made Of': An affectionate look at five middle-aged men

Boys to men

The Backstreet Boys might be middle-aged, married and have dodgy knees, but a heartfelt documentary reveals they’re not going gently into pop’s good night
Crufts 2015: Should foreign dogs be allowed to compete?

Crufts 2015

Should foreign dogs be allowed to compete?
10 best projectors

How to make your home cinema more cinematic: 10 best projectors

Want to recreate the big-screen experience in your sitting room? IndyBest sizes up gadgets to form your film-watching
Manchester City 1 Barcelona 2 player ratings: Luis Suarez? Lionel Messi? Joe Hart? Who was the star man?

Manchester City vs Barcelona player ratings

Luis Suarez? Lionel Messi? Joe Hart? Who was the star man at the Etihad?
Arsenal vs Monaco: Monaco - the making of Gunners' manager Arsene Wenger

Monaco: the making of Wenger

Jack Pitt-Brooke speaks to former players and learns the Frenchman’s man-management has always been one of his best skills
Cricket World Cup 2015: Chris Gayle - the West Indies' enigma lives up to his reputation

Chris Gayle: The West Indies' enigma

Some said the game's eternal rebel was washed up. As ever, he proved he writes the scripts by producing a blistering World Cup innings
In Ukraine a dark world of hybrid warfare and murky loyalties prevails

In Ukraine a dark world of hybrid warfare

This war in the shadows has been going on since the fall of Mr Yanukovych
'Birdman' and 'Bullets Over Broadway': Homage or plagiarism?

Homage or plagiarism?

'Birdman' shares much DNA with Woody Allen's 'Bullets Over Broadway'
Broadchurch ends as damp squib not even David Tennant can revive

A damp squib not even David Tennant can revive

Broadchurch, Series 2 finale, review
A Koi carp breeding pond, wall-mounted iPads and a bathroom with a 'wellness' shower: inside the mansion of Germany's 'Bishop of Bling'

Inside the mansion of Germany's 'Bishop of Bling'

A Koi carp breeding pond, wall-mounted iPads and a bathroom with a 'wellness' shower