'Shell-Shocked' crabs can feel pain too

Scientists have proven that crabs and other crustaceans do feel pain, and are able to recall an unpleasant experience and take action to avoid it happening again.

The latest study by Professor Bob Elwood and Barry Magee from Queen's School of Biological Sciences looked at the reactions of common shore crabs to small electrical shocks, and their behaviour after experiencing those shocks.

Elwood's previous research showed that prawns and hermit crabs respond in a way consistent with pain.

"The experiment was carefully designed to distinguish between pain and a reflex phenomenon known as nociception. The function of pain is to aid future avoidance of the pain source, whereas nociception enables a reflex response that provides immediate protection but no awareness or changes to long-term behaviour," Elwood said in a statement.

This latest study showed that shore crabs are willing to trade something of value to them - in this case a dark shelter - to avoid future electric shock.

Ninety crabs were each introduced individually to a tank with two dark shelters. On selecting their shelter of choice, some of the crabs were exposed to an electric shock. After some rest time, each crab was returned to the tank.

Most stuck with what they knew best, returning to the shelter they had chosen first time around, where those that had been shocked on first choice again experienced a shock.

When introduced to the tank for the third time, however, the vast majority of shocked crabs now went to the alternative safe shelter. Those not shocked continued to use their preferred shelter.

"Having experienced two rounds of shocks, the crabs learned to avoid the shelter where they received the shock. They were willing to give up their hideaway in order to avoid the source of their probable pain," said Elwood.

Elwood says that his research highlights the need to investigate how crustaceans used in food industries, such as crabs, prawns and lobsters, are treated.

"Billions of crustacean are caught or reared in aquaculture for the food industry. In contrast to mammals, crustaceans are given little or no protection as the presumption is that they cannot experience pain," he said.

The study was published in the Journal of Experimental Biology.