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Title: Pain in crustaceans? : examining avoidance learning and trade-offs
Author: Magee , Barry Thomas
ISNI:       0000 0004 6425 0332
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2017
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The study of pain generates interest for medical, scientific and ethical reasons. Understanding how pain works allows the prevention/reduction of pain in the treatment of patients, promotes the development of analgesics and can be incorporated into animal welfare concerns. There are two distinct components of pain. Nociception is the sensory mechanism that allows detection of noxious stimuli and enables a reflex response, it is the physiological aspect of pain but infers no aversive emotional experience. The emotional component is termed pain and involves awareness, interpretation, and assessment of the perception. We examined whether shore crabs placed within a brightly lit chamber learn to avoid one of two dark shelters when that shelter results in shock. Those that received shock in trial 2, irrespective of shock in trial 1, were more likely to switch shelter choice and thus showed rapid discrimination. We also placed shore crabs alternately in two halves of a test area divided by ab opaque partition. Each area had a dark shelter and in one repeated small electric shocks were delivered. Despite the lack of discrimination learning between the two shelters they used other tactics to reduce the amount of shock received. Examining potential trade-offs between noxious stimuli and other motivational factors may highlight a decision making process occurring that would fulfil a criterion of pain. We examined the responses of shore crabs to electric shock within a dark shelter when presented with different light intensities outside the shelter. The light intensity had no effect on whether the crab entered the shelter or the number of shocks taken to induce exit from the shelter. We further examined the responses of hermit crabs to electric shock within their shell when also exposed to predator or non­predator odours or to no odour. The data show that these crabs trade-off avoidance of electric shock with predator avoidance. They are thus not responding purely by reflex and the data are thus consistent with predictions of pain but do not prove pain.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available