Lobsters and crabs feel pain, study shows

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Lobsters and crabs feel pain, study shows

Findings add to growing evidence that virtually all animals can suffer

By Jennifer Viegas

Discovery Channel

updated 8:53 a.m. PT, Fri., March. 27, 2009

Ripping the legs off live crabs and crowding

lobsters into seafood market tanks are just two

of the many practices that may warrant

reassessment, given two new studies that indicate

crustaceans feel pain and stress.

The findings add to a growing body of evidence

that virtually all animals, including fish,

shellfish and insects, can suffer.

Robert Elwood, the lead author of both papers,

explained to Discovery News that pain allows an

individual to be " aware of the potential tissue

damage " while experiencing " a huge negative

emotion or motivation that it learns to avoid

that situation in the future. "

Both pain and stress are therefore key survival mechanisms.

Elwood, a professor in the School of Biological

Sciences at The Queen's University in Belfast,

and colleague Mirjam Appel studied hermit crabs

collected from rock pools in County Down,

Northern Ireland. All of the crabs survived the

experiments and were later released back into

their native habitat.

Elwood and Appel gave small electric shocks to

some of the crabs within their shells. When the

researchers provided vacant shells, some crabs -

but only the ones that had been shocked -left

their old shells and entered the new ones,

showing stress-related behaviors like grooming of

the abdomen or rapping of the abdomen against the

empty shell.

Grooming, as for a person licking a burnt finger,

" is a protective motor reaction and viewed as a

sign of pain in vertebrates, " the researchers

wrote.

It has been thought that the behavior of

crustaceans is mostly reflexive, but the fact

that they showed signs of physical distress at

the same time they changed a behavior - in this

case, moving into another shell - suggest they

feel pain as well, according to the researchers.

The research has been accepted for publication in the journal Animal Behavior.

For the second paper, slated for publication in

the journal Applied Animal Behavior Science,

Elwood, along with Stuart Barr and Lynsey

Patterson, outline seven reasons, with supportive

findings, they believe crustaceans suffer.

For one thing, they argue, crustaceans possess " a

suitable central nervous system and receptors. "

They learn to avoid a negative stimulus after a

potentially painful experience. They also engage

in protective reactions, such as limping and

rubbing, after being hurt.

Physiological changes, including release of

adrenal-like hormones, also occur when pain or

stress is suspected. And the animals make future

decisions based on past likely painful events.

If crabs are given medicine - anesthetics or

analgesics - they appear to feel relieved,

showing fewer responses to negative stimuli. And

finally, the researchers wrote, crustaceans

possess " high cognitive ability and sentience. "

In the past, some scientists reasoned that since

pain and stress are associated with the neocortex

in humans, all creatures must have this brain

structure in order to experience such feelings.

More recent studies, however, suggest that

crustacean brains and nervous systems are

configured differently. For example, fish,

lobsters and octopi all have vision, Elwood said,

despite lacking a visual cortex, which allows

humans to see.

It was also thought that since many invertebrates

cast off damaged appendages, it was not harmful

for humans to remove legs, tails and other body

parts from live crustaceans. Another study led by

Patterson, however, found that when humans

twisted off legs from crabs, the stress response

was so profound that some individuals later died

or could not regenerate the lost appendages.

Chris Sherwin, a senior research fellow in the

Clinical Veterinary Science division at the

University of Bristol, has also studied pain in

invertebrates.

 

Sherwin told Discovery News, " The question of

whether invertebrates experience pain is

fundamental to our legislation that protects

animals and our behavior, attitude and use of

these highly complex organisms. "

He said that while the recent studies suggest

crustaceans experience " something akin to pain,

rather than fixed, reflex responses, " additional

research is needed.

More on crustaceans | pain

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URL: http://www.msnbc.msn.com/id/29915025/

 

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