Do Crustaceans Feel Pain?

Do lobsters, crabs and other crustaceans feel pain? We certainly act as if they don’t, tossing them and placing them in tanks with their claws wired shut. And then there’s the cooking itself — most chefs cook crabs and lobsters alive, usually by dumping them into a pot of boiling water.

Do Crustaceans Feel Pain?We might feel a frisson of guilt, whenever we see those creatures rattling around inside the pot as the water boils. But that feeling usually dissolves for those crustacean lovers by the time we crack open a claw and dig out their mouth watering meat.

According to recent findings published in Biology Letters last week, crustaceans experience pain.

Do Crustaceans Feel Pain?Most invertebrates, except cephalopods like octopuses, are thought not to feel pain because they lack pain receptors in their brain. However, a recent work defined animal pain using a series of expectations or criteria: There should be a physiological stress response associated with noxious stimuli, as well as changes in behavior to protect themselves from further damage, such as increased wariness. While stress responses of crustaceans have been demonstrated in shore crabs, hermit crabs, and crayfish, these are typically preceded by escape behavior. So it’s hard to say if the physiological change is because of pain. 

Do Crustaceans Feel Pain?To investigate, Robert Elwood and Laura Adams of Queen’s University collected 40 European shore crabs (Carcinus maenas) from Portaferry in Northern Ireland. A copper wire was placed around the joint on their fifth walking legs, and for 20 of them in the “shocked” group, that wire was attached to an electric stimulator. Then the team delivered 10-volt, 180-hertz shocks for 200 milliseconds every 10 seconds for two minutes.

The other 20, “non-shocked” crabs served as controls. The crabs were categorized into three types: no movement throughout, walking but no extreme response, and extreme response, which includes threat postures and attempts to climb the walls of the tank. Four minutes later, the team collected a sample of their vital fluid (called hemolymph) and measured the levels of lactate, which indicate the stress response. 

They found higher levels of lactate in shore crabs exposed to brief electric shock than in non-shocked controls. But, since shocked crabs showed more vigorous behavior, the team then matched the crabs with the same level of behavior: Walking shocked crabs were compared to walking non-shocked crabs. Even then, they still found that shocked crabs had stronger stress responses.

Do Crustaceans Feel Pain?These results, together with previous findings on behavioral changes and avoidance learning, suggest that crabs fulfill the criteria expected of a pain experience.

In the U.K., vertebrates are protected in scientific investigations, and this protection was recently extended to cephalopods. The vast majority of invertebrates have no such protection. 


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