Pain and stress in crustaceans
|Queen’s University Belfast, Biological Sciences, UK|
Pain and stress are subject to natural selection and they are of clear benefit to animals and humans. They enable the animal to respond in adaptive ways to noxious, potentially damaging stimuli and situations. We may thus expect pain and stress to be widely spread among taxa, however, investigations have concentrated on the vertebrates with invertebrates receiving little interest. Here I consider studies on possible pain perception in the glass prawn and stress responses in the edible crab.
Glass prawns had one antenna treated with either water or a local anaesthetic and the responses noted. The same antenna was then treated to acetic acid, sodium hydroxide, mechanical abuse or water and the responses noted again. There was no change in overall activity following these treatments, however, those receiving chemical abuse groomed the antenna more and rubbed it on the side of the tank more than those with water or mechanical abuse. This response was specific to the treated and not the untreated antenna and was reduced if the antenna had been pre-treated with local anaesthetic. These findings are consistent with pain perception.
Edible crabs were subjected to the commercial fishery practice of de-clawing, where one or two claws may be removed and the animal returned to the sea. The removal of one claw caused changes that are consistent with a physiological stress response, involving an increase in lactate and mobilisation of glycogen to glucose within 10 minutes, and this response was still apparent after 24 hrs. The response was increased if the crab was kept with a similar sized intact crab rather than being held alone. Crabs induced to autotomise one claw showed a significantly lower physiological response, and the wound caused by claw loss was much smaller. About 18% of crabs died after de-clawing but none died after autotomy. This stress response is caused by release of Crustacean Hyperglycaemic Hormone and is analogous to the stress response of vertebrates.
Our data suggest that decapod crustaceans are capable of perceptions hitherto neglected by science and by food production industries.