Pain in crustaceans: Difference between revisions

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[[File:Crabhalf.jpg|thumb|right|This [[tanner crab]] was quickly cut in half before cooking]]
[[File:Crabhalf.jpg|thumb|right|This [[tanner crab]] was quickly cut in half before cooking]]


A 2007 study at Queen's University, Belfast, suggested that crustaceans do feel pain.<ref name="elwood2007">{{Cite journal|author=Stuart Barr, Peter R. Laming, Jaimie T. A. Dick & Robert W. Elwood |year=2007 |title=Nociception or pain in a decapod crustacean? |journal=[[Animal Behaviour (journal)|Animal Behaviour]] |volume=75 |issue=3 |pages=745–751 |doi=10.1016/j.anbehav.2007.07.004}}</ref> In the experiment, when the antennae of prawns were rubbed with [[sodium hydroxide]] or [[acetic acid]], the animals showed increased grooming of the afflicted area and rubbed it more against the side of the tank. Moreover, this reaction was inhibited by a local anesthetic, even though control prawns treated with only anesthetic did not show reduced activity. Robert Elwood, who headed the study, argues that sensing pain is crucial to prawn survival, because it encourages them to avoid damaging behaviors. Some scientists responded, saying the rubbing may reflect an attempt to clean the affected area.<ref>{{cite news |author=Ian Sample |url=http://www.guardian.co.uk/science/2007/nov/08/animalrights.sciencenews |title=Blow for fans of boiled lobster: crustaceans feel pain, study says |publisher=[[The Guardian]] |date=November 8, 2007}}</ref>
A 2008 study at Queen's University, Belfast, suggested that crustaceans do feel pain.<ref name="elwood2008">{{Cite journal|author=Stuart Barr, Peter R. Laming, Jaimie T. A. Dick & Robert W. Elwood |year=2008 |title=Nociception or pain in a decapod crustacean? |journal=[[Animal Behaviour (journal)|Animal Behaviour]] |volume=75 |issue=3 |pages=745–751 |doi=10.1016/j.anbehav.2007.07.004}}</ref> In the experiment, when the antennae of prawns were rubbed with [[sodium hydroxide]] or [[acetic acid]], the animals showed increased grooming of the afflicted area and rubbed it more against the side of the tank. Moreover, this reaction was inhibited by a local anesthetic, even though control prawns treated with only anesthetic did not show reduced activity. Robert Elwood, who headed the study, argues that sensing pain is crucial to prawn survival, because it encourages them to avoid damaging behaviors. Some scientists responded, saying the rubbing may reflect an attempt to clean the affected area.<ref>{{cite news |author=Ian Sample |url=http://www.guardian.co.uk/science/2007/nov/08/animalrights.sciencenews |title=Blow for fans of boiled lobster: crustaceans feel pain, study says |publisher=[[The Guardian]] |date=November 8, 2007}}</ref> For example, application of anesthetic alone caused an increase in grooming. Several key effects were not replicated in an independent project, which found no behavioural or neural changes in three species in response to acids or bases.<ref name=puri2010>{{cite journal|author=Puri S, Faulkes Z|year=2010|title=Do decapod crustaceans have nociceptors for extreme pH?|journal=[[''PLOS ONE'']]|volume=5|issue=4|pages=e10244|doi=10.1371/journal.pone.0010244|url=http://dx.doi.org/10.1371/journal.pone.0010244}}</ref>


In a subsequent 2009 study, Elwood and Mirjam Appel showed that [[hermit crab]]s make motivational tradeoffs between electric shocks and the quality of the shells they inhabit.<ref name="elwood2009">{{Cite journal|author=Robert W. Elwood & Mirjam Appel |year=2009 |title=Pain experience in hermit crabs? |journal=[[Animal Behaviour (journal)|Animal Behaviour]] |volume=77 |issue=5 |pages=1243–1246 |doi=10.1016/j.anbehav.2009.01.028 |url=http://www.mbl.edu/research/services/iacuc/pdf/pain_hermit_crabs.pdf |format=[[Portable Document Format|PDF]]}}</ref> In particular, as hermit crabs are shocked more intensely, they become increasingly willing to leave their current shells for new shells, and they spend less time deciding whether to enter those new shells. Moreover, because the researchers did not offer the new shells until after the electrical stimulation had ended, the change in motivational behavior was the result of memory of the noxious event, not an immediate reflex. Similarly, it has been shown that crabs will discard a valuable resource (a preferred shelter) in order to avoid future encounters with painful stimuli, thereby indicating avoidance learning - a key criterion of the ability to experience pain.<ref name=elwood2013>{{cite journal|author=Robert W. Elwood and Barry Magee|year=2013|title=Shock avoidance by discrimination learning in the shore crab (Carcinus maenas) is consistent with a key criterion for pain|journal=[[Journal of Experimental Biology]]|doi=10.1242/jeb.072041|url=http://jeb.biologists.org/content/216/3/353.abstract}}</ref>
In a subsequent 2009 study, Elwood and Mirjam Appel showed that [[hermit crab]]s make motivational tradeoffs between electric shocks and the quality of the shells they inhabit.<ref name="elwood2009">{{Cite journal|author=Robert W. Elwood & Mirjam Appel |year=2009 |title=Pain experience in hermit crabs? |journal=[[Animal Behaviour (journal)|Animal Behaviour]] |volume=77 |issue=5 |pages=1243–1246 |doi=10.1016/j.anbehav.2009.01.028 |url=http://www.mbl.edu/research/services/iacuc/pdf/pain_hermit_crabs.pdf |format=[[Portable Document Format|PDF]]}}</ref> In particular, as hermit crabs are shocked more intensely, they become increasingly willing to leave their current shells for new shells, and they spend less time deciding whether to enter those new shells. Moreover, because the researchers did not offer the new shells until after the electrical stimulation had ended, the change in motivational behavior was the result of memory of the noxious event, not an immediate reflex. Similarly, it has been shown that crabs will discard a valuable resource (a preferred shelter) in order to avoid future encounters with painful stimuli, thereby indicating avoidance learning - a key criterion of the ability to experience pain.<ref name=elwood2013>{{cite journal|author=Robert W. Elwood and Barry Magee|year=2013|title=Shock avoidance by discrimination learning in the shore crab (Carcinus maenas) is consistent with a key criterion for pain|journal=[[Journal of Experimental Biology]]|doi=10.1242/jeb.072041|url=http://jeb.biologists.org/content/216/3/353.abstract}}</ref>

Revision as of 15:50, 9 August 2013

Close up of the head of live lobster shipped for consumption in the United States

The question of whether or not crustaceans can experience pain is unresolved. Because of the ambiguous nature of pain, most people who contend that crustaceans do have this capacity approach the issue using "argument by analogy" – that is, they hold that certain similarities between crustacean and human biology or behaviour warrant an assumption that crustaceans can feel pain.[1]

In vertebrates, endogenous opioids are neurochemicals that moderate pain by interacting with opioid receptors. Opioid peptides and opioid receptors occur naturally in crustaceans, and although "at present no certain conclusion can be drawn",[2] some have interpreted their presence as an indication that crustaceans may be able to experience pain.[1][2] Lobsters' opioids may "mediate pain in the same way" as in vertebrates.[1]

Background

See also: Pain in animals and Pain in invertebrates

The idea that animals might not feel pain in the same manner as humans do dates back at least to the 17th-century, when French philosopher René Descartes argued that animals do not experience pain because they lack consciousness.[3][4][5] Bernard Rollin of Colorado State University, the principal author of two U.S. federal laws regulating pain relief for animals, wrote that researchers remained unsure into the 1980s as to whether animals experience pain. Veterinarians trained in the U.S. before 1989 were simply taught to ignore animal pain.[6] In his interactions with scientists and other veterinarians, Bernard Rollin was regularly asked to "prove" that animals are conscious and to provide "scientifically acceptable" grounds for claiming that they feel pain.[6] Veterinarian and author Larry Carbone has written that the view that animals feel pain differently is now a minority view. Academic reviews of the topic are more equivocal, noting that although the argument that animals have at least simple conscious thoughts and feelings has strong support,[7] some critics continue to question how reliably animal mental states can be determined.[4][8]

The presence of pain in an animal, or another human for that matter, cannot be known for sure, but it can be inferred through physical and behavioral reactions.[9][10][11] Specialists currently believe that all vertebrates can feel pain, and that certain invertebrates, like the octopus, might too.[12][13] Nociceptors, the neurones required for the sensation of pain, have been found in nematodes, annelids, molluscs[14] and in the arthropod, Drosophila,[15] despite earlier claims that nociceptors were absent in insects.[16]

As for other animals, plants, or other entities, their ability to feel physical pain is at present a question beyond scientific reach, since no mechanism is known by which they could have such a feeling. In particular, there are no known nociceptors in groups such as plants and fungi.

For actual or potential animal pain, veterinary medicine uses the same analgesics and anesthetics as those used in humans.[17]

Research findings

A squat lobster, Eumunida picta

In February 2005, a review of the literature by the Norwegian Scientific Committee for Food Safety tentatively concluded that "it is unlikely that [lobsters] can feel pain," though they note that "there is apparently a paucity of exact knowledge on sentience in crustaceans, and more research is needed." This conclusion is based on the lobster's simple nervous system. The report assumes that the violent reaction of lobsters to boiling water is a reflex to noxious stimuli.[2]

However, review by the Scottish animal welfare group Advocate for Animals released in the same year reported that "scientific evidence ... strongly suggests that there is a potential for [lobsters] to experience pain and suffering". This is primarily because lobsters (and other decapod crustaceans) "have opioid receptors and respond to opioids (analgesics such as morphine) in a similar way to vertebrates", indicating that lobsters' reaction to injury changes when painkillers are applied. The similarities in lobsters' and vertebrates' stress systems and behavioral responses to noxious stimuli were given as additional evidence for their capacity for pain.[1]

This tanner crab was quickly cut in half before cooking

A 2008 study at Queen's University, Belfast, suggested that crustaceans do feel pain.[18] In the experiment, when the antennae of prawns were rubbed with sodium hydroxide or acetic acid, the animals showed increased grooming of the afflicted area and rubbed it more against the side of the tank. Moreover, this reaction was inhibited by a local anesthetic, even though control prawns treated with only anesthetic did not show reduced activity. Robert Elwood, who headed the study, argues that sensing pain is crucial to prawn survival, because it encourages them to avoid damaging behaviors. Some scientists responded, saying the rubbing may reflect an attempt to clean the affected area.[19] For example, application of anesthetic alone caused an increase in grooming. Several key effects were not replicated in an independent project, which found no behavioural or neural changes in three species in response to acids or bases.[20]

In a subsequent 2009 study, Elwood and Mirjam Appel showed that hermit crabs make motivational tradeoffs between electric shocks and the quality of the shells they inhabit.[21] In particular, as hermit crabs are shocked more intensely, they become increasingly willing to leave their current shells for new shells, and they spend less time deciding whether to enter those new shells. Moreover, because the researchers did not offer the new shells until after the electrical stimulation had ended, the change in motivational behavior was the result of memory of the noxious event, not an immediate reflex. Similarly, it has been shown that crabs will discard a valuable resource (a preferred shelter) in order to avoid future encounters with painful stimuli, thereby indicating avoidance learning - a key criterion of the ability to experience pain.[22]

Morphine, an analgesic, and naloxone, an opioid receptor antagonist, may affect the estuarine crab Neohelice granulata in much the same way they affect vertebrates: injections of morphine into crabs produced a dose-dependent reduction of their defensive response to an electric shock.[23] (However, the attenuated defensive response could originate from either the analgesic or sedative properties of morphine, or both.)[24] These findings have been replicated for other invertebrate species,[24] but similar data are not yet available for lobsters.

See also

References

  1. ^ a b c d Cephalopods and decapod crustaceans: their capacity to experience pain and suffering (PDF). Advocates for Animals. 2005.
  2. ^ a b c L. Sømme (2005). "Sentience and pain in invertebrates: Report to Norwegian Scientific Committee for Food Safety". Norwegian University of Life Sciences, Oslo.
  3. ^ Larry Carbone (2004). What Animals Want: Expertise and Advocacy in Laboratory Animal Welfare Policy. Oxford University Press. p. 149. ISBN 978-0-19-516196-0.
  4. ^ a b The Ethics of research involving animals Nuffield Council on Bioethics, Accessed 27 February 2008 Template:Wayback
  5. ^ Bernard E. Rollin (2007). "Animal research: a moral science. Talking Point on the use of animals in scientific research". EMBO reports. 8 (6): 521–525. doi:10.1038/sj.embor.7400996. PMC 2002540. PMID 17545990. {{cite journal}}: |chapter= ignored (help)
  6. ^ a b Bernard Rollin (1989). The Unheeded Cry: Animal Consciousness, Animal Pain, and Science. New York: Oxford University Press. pp. xii, 117–118. ISBN 978-0-19-286104-7. Cited in Carbone 2004, p. 150.
  7. ^ Donald R. Griffin & Gayle B. Speck (2004). "New evidence of animal consciousness". Animal Cognition. 7 (1): 5–18. doi:10.1007/s10071-003-0203-x. PMID 14658059.
  8. ^ Colin Allen (1998). "Assessing animal cognition: ethological and philosophical perspectives" (PDF). Journal of Animal Science. 76 (1): 42–47. PMID 9464883.
  9. ^ Frances V. Abbott, Keith B. J. Franklin & R. Frederick Westbrook (1995). "The formalin test: scoring properties of the first and second phases of the pain response in rats". Pain. 60 (1): 91–102. doi:10.1016/0304-3959(94)00095-V. PMID 7715946. {{cite journal}}: Unknown parameter |month= ignored (help)
  10. ^ Sherwin, C.M., (2001). Can invertebrates suffer? Or, how robust is argument-by-analogy? Animal Welfare, 10 (supplement): S103-S118
  11. ^ Elwood, R.W., (2011). Pain and suffering in invertebrates? Institute of Laboratory Animal Resources Journal, 52(2): 175-84 [1]
  12. ^ The Senate Standing Committee on Legal and Constitutional Affairs. "Do invertebrates feel pain?". Parliament of Canada. Retrieved June 11, 2008.
  13. ^ Jane A. Smith (1991). "A question of pain in invertebrates". ILAR Journal. 33 (1–2): 25–31.
  14. ^ St John Smith, E. and Lewin, G.R., (2009). Nociceptors: a phylogenetic view. Journal of Comparative Physiology A Neuroethology Sensory Neural and Behavioral Physiology, 195: 1089-1106
  15. ^ W. Daniel Tracey, Jr., Rachel I. Wilson, Gilles Laurent & Seymour Benzer (2003). "painless, a Drosophila gene essential for nociception". Cell. 113 (2): 261–273. doi:10.1016/S0092-8674(03)00272-1. PMID 12705873.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  16. ^ C. H. Eisemann, W. K. Jorgensen, D. J. Merritt, M. J. Rice, B. W. Cribb, P. D. Webb & M. P. Zalucki (1984). "Do insects feel pain? – A biological view" (PDF). Cellular and Molecular Life Sciences. 40: 1420–1423.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  17. ^ Ignacio Viñuela-Fernández, Emma Jones, Elizabeth M. Welsh & Susan M. Fleetwood-Walker (2007). "Pain mechanisms and their implication for the management of pain in farm and companion animals". The Veterinary Journal. 174 (2): 227–239. doi:10.1016/j.tvjl.2007.02.002. PMID 17553712. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  18. ^ Stuart Barr, Peter R. Laming, Jaimie T. A. Dick & Robert W. Elwood (2008). "Nociception or pain in a decapod crustacean?". Animal Behaviour. 75 (3): 745–751. doi:10.1016/j.anbehav.2007.07.004.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  19. ^ Ian Sample (November 8, 2007). "Blow for fans of boiled lobster: crustaceans feel pain, study says". The Guardian.
  20. ^ Puri S, Faulkes Z (2010). "Do decapod crustaceans have nociceptors for extreme pH?". PLOS ONE. 5 (4): e10244. doi:10.1371/journal.pone.0010244. {{cite journal}}: Italic or bold markup not allowed in: |journal= (help)CS1 maint: unflagged free DOI (link)
  21. ^ Robert W. Elwood & Mirjam Appel (2009). "Pain experience in hermit crabs?" (PDF). Animal Behaviour. 77 (5): 1243–1246. doi:10.1016/j.anbehav.2009.01.028.
  22. ^ Robert W. Elwood and Barry Magee (2013). "Shock avoidance by discrimination learning in the shore crab (Carcinus maenas) is consistent with a key criterion for pain". Journal of Experimental Biology. doi:10.1242/jeb.072041.
  23. ^ M. Lozada, A. Romano & H. Maldonado (1988). "Effect of morphine and naloxone on a defensive response of the crab Chasmagnathus granulatus". Pharmacology Biochemistry and Behavior. 30 (3): 635–640. doi:10.1016/0091-3057(88)90076-7.
  24. ^ a b V. E. Dyakonova (2001). "Role of opioid peptides in behavior of invertebrates". Journal of Evolutionary Biochemistry and Physiology. 37 (4): 335–347. doi:10.1023/A:1012910525424.

Further reading

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