Tasteless: Crabs remember pain

It's a research which might spoil your craving for the delicious crab meat -- the creatures not only suffer pain but they retain a memory of it.

There has been a long debate about whether crustaceans including crabs, prawns and lobsters feel pain. Now, a team at Queen's University in Belfast has shown that crabs endure pain and remember it too.

"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. Such trade-offs are seen in vertebrates in which the response to pain is controlled with respect to other requirements.

"Humans, for example, may hold on a hot plate that contains food whereas they may drop an empty plate, showing that we take into account differing motivational requirements when responding to pain.

"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," lead researcher Prof Bob Elwood said.

In the study, the researchers looked at the reactions of hermit crabs to small electric shocks. Wires were attached to shells to deliver the small shocks to the abdomen of the some of the crabs within the shells.

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 central neuronal processing occurs rather than the response merely being a reflex.

According to the researchers, 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 and were more likely to change to the new shell compared to those that had not been shocked, they found.

According to Prof Elwood, the research highlighted the need to investigate how crustaceans used in food industries are treated.

"Millions of crustacean are caught or reared in aquaculture for the food industry. There is no protection for these animals as the presumption is that they can't experience pain," he said.

The findings of the study have been published in the 'Animal Behaviour' journal.