Chefs who prepare crustaceans by dropping them into boiling water while alive might now be feeling guilty, as scientists have provided evidence to suggest that invertebrates, such as prawns, can feel pain.
Biologists from the School of Biological Sciences at Queen's University, Belfast, examined how prawns reacted to noxious stimuli and believe they have found evidence to demonstrate that the invertebrates can feel pain.
When acetic acid was dabbed onto the antennae of the prawn, Palaemon elegans, it elicited an immediate reflex tail reflex response - something known as nociception. The prawn also undertook some prolonged "grooming" activities on the affected antenna.
The researchers believe that these behaviours might indicate that the prawns felt pain as a result of the stimuli applied.
Anaesthetic testWhen the antenna was numbed with the drug benzocaine, a local anaesthetic, both sets of responses were inhibited.
The authors explained: "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."
Many experts previously believed that only vertebrate animals felt pain.
Cephalopods, such as octopus and cuttlefish, which have a larger central nervous system (CNS), and they are afforded legal protection in the UK when used in studies, while other invertebrates are not.
For more information see the paper: Barr S, Laming PR, Dick JTA and RW Elwood (2007) - Nociception or pain in a decapod crustacean? Animal Behaviour, doi:10.1016/j.anbehav.2007.07.004.