Measurements show crabs can treat pain

Researchers at the University of Gothenburg are the first to prove that painful stimuli are sent to the brains of shore crabs, providing more evidence for pain in crustaceans. EEG-like measurements show clear neuronal reactions in the crustacean brain upon mechanical or chemical stimulation.

The study is published in the journal Biology.

In the search for better welfare of the animals that humans kill for food, researchers at the University of Gothenburg have chosen to focus on decapod crustaceans. This includes shellfish specialties such as shrimp, lobsters, crabs and crayfish that we catch both wild and farmed. Currently, shellfish are not covered by EU animal welfare legislation, but this could be about to change. For good reason, according to researchers.

“We need to find less painful ways to kill shellfish if we want to continue eating them. Because we now have scientific evidence that they feel and respond to pain,” says Lynne Sneddon, a zoophysiologist at the University of Gothenburg.

Several research groups have already conducted a number of observational studies on crustaceans where they were subjected to mechanical impacts, electric shocks or acids on soft tissues such as antennae. These crustaceans responded by touching the exposed area or trying to avoid danger in repeated experiments, leading researchers to assume they felt pain.

Pain receptors in soft tissues

Researchers from the University of Gothenburg are the first to carry out neurobiological studies by measuring the brain activity of a shore crab, using an EEG-type measurement.

“We were able to see that the crab has some sort of pain receptors in its soft tissues because we recorded an increase in brain activity when we applied a potentially painful chemical, a form of vinegar, to the soft tissues. “The same thing happened when we applied external pressure to several parts of the crab’s body,” says Eleftherios Kasiouras, a Ph.D. student at the University of Gothenburg and lead author of the study.

The activity of the brain’s central nervous system was measured in the crab when the soft tissues of the claws, antennae and legs were subjected to some form of stress. The answers show that shore crabs must feel some form of pain signaling to the brain from these body parts. The pain response was shorter and more powerful in the case of physical stress than in the case of chemical stress, which lasted longer.

Cut alive

“It stands to reason that all animals need some sort of pain-relieving system to cope and avoid danger. I don’t think we need to test every species of crustacean, because they have a similar structure and therefore a similar nervous system We can assume that shrimp, crayfish and lobsters can also send external signals regarding painful stimuli to their brain, which will process this information,” explains Kasiouras.

Researchers emphasize that we need to find more humane ways to handle, or even kill, shellfish. Currently, it is permitted to cut up a live crustacean, unlike the mammals we consume.

“We need more research to find less painful ways to kill shellfish,” Sneddon says.