As a follow-up to my previous post on speciesism, it is of interest that a soon to be published paper in Animal Behaviour provides tentative evidence of pain in decapod crustaceans (which includes lobsters, crayfishes [crawfishes or crawdads], crabs, shrimps, and prawns). I came across this through a news report in New Scientist that showed up in my RSS feeds and it seemed worthy of mentioning.
Both the New Scientist report and the primary article are behind subscription walls, but here is the abstract of the paper:
Nociception or pain in a decapod crustacean?
Nociception is the ability to perceive a noxious stimulus and react in a reflexive manner and occurs across a wide range of taxa. However, the ability to experience the associated aversive sensation and feeling, known as pain, is not widely accepted to occur in nonvertebrates. We examined the responses of a decapod crustacean, the prawn, Palaemon elegans, to different noxious stimuli applied to one antenna to assess reflex responses (nociception) and longer-term, specifically directed behavioural responses that might indicate pain. We also examined the effects of benzocaine, a local anaesthetic, on these responses. Noxious stimuli elicited an immediate reflex tail flick response, followed by two prolonged activities, grooming of the antenna and rubbing of the antenna against the side of the tank, with both activities directed specifically at the treated antenna. These responses were inhibited by benzocaine; however, benzocaine did not alter general swimming activity and thus the decline in grooming and rubbing is not due to general anaesthesia. Mechanical stimulation by pinching also resulted in prolonged rubbing, but this was not inhibited by benzocaine. These results indicate an awareness of the location of the noxious stimuli, and the prolonged complex responses indicate a central involvement in their organization. The inhibition by a local anaesthetic is similar to observations on vertebrates and is consistent with the idea that these crustaceans can experience pain.
Let me say this before the comments begin: I don’t think anyone is claiming that prawns can experience the same kind of pain, including emotional pain and anticipation of pain, that humans can. The point is simply that we cannot automatically dismiss all reactions to noxious stimuli in invertebrates as reflexive nociception. There could be something more to it.