Crabs feel pain and remember it
New research shows crabs can not only suffer pain but retain a memory of it
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Friday, 27, Mar 2009 07:45
New research shows crabs can not only suffer pain but retain a memory of it.
A study published in the journal Animal Behaviour looked at the reactions of hermit crabs to small electric shocks.
The authors claim the results highlight the need to investigate how crustaceans used in food industries are treated.
During the study wires were attached to shells to deliver small shocks to the abdomen of some of the crabs inside.
The authors write: "The only crabs to get out of their shells were those which had received shocks, indicating that the experience is unpleasant for them. This shows that central neuronal processing occurs rather than the response merely being a reflex."
The study also found the crabs were more likely to come out of shells they didn't like.
Researchers claim the main aim of the experiment was to deliver a shock just under the threshold that causes crabs to move out of the shell, to see what happened when a new shell was then offered.
Crabs that had been shocked but had remained in their shell appeared to remember the experience of the shock because they quickly moved towards the new shell, investigated it briefly and were more likely to change to the new shell compared to those that had not been shocked, the authors of today's report explain.
Professor Bob Elwood from the School of Biological Sciences at Queen's University Belfast and said: "There has been a long debate about whether crustaceans including crabs, prawns and lobsters feel pain.
"We know from previous research that they can detect harmful stimuli and withdraw from the source of the stimuli but that could be a simple reflex without the inner 'feeling' of unpleasantness that we associate with pain.
"This research demonstrates that it is not a simple reflex but that crabs trade-off their need for a quality shell with the need to avoid the harmful stimulus.
"Trade-offs of this type have not been previously demonstrated in crustaceans. The results are consistent with the idea of pain being experienced by these animals."
Previous work at Queen's University found that prawns show prolonged rubbing when an antenna was treated with weak acetic acid but this rubbing was reduced by local anaesthetic.
The findings are both studies are consistent with observations of pain in mammals.
But Professor Elwood says that in contrast to mammals, little protection is given to the millions of crustaceans that are used in the fishing and food industries each day.
He added: "More research is needed in this area where a potentially very large problem is being ignored."