Pain in crustaceans
Encyclopedia
The question of whether or not crustacean
s 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.
In vertebrate
s, endogenous opioid
s 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", some have interpreted their presence as an indication that crustaceans may be able to experience pain. Lobsters' opioids may "mediate pain in the same way" as in vertebrates.
as human beings feel it traces back to the 17th-century French philosopher, René Descartes
, who argued that animals do not experience pain, because they lack consciousness
. Bernard Rollin
of Colorado State University, the principal author of two U.S. federal laws regulating pain relief for animals, writes that researchers remained unsure into the 1980s as to whether animals experience pain, and veterinarians trained in the U.S. before 1989 were simply taught to ignore animal pain. 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. Carbone writes 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, some critics continue to question how reliably animal mental states can be determined.
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. Specialists currently believe that all vertebrates can feel pain, and that certain invertebrates, like the octopus, might too. Nociceptors, the neurones required for the sensation of pain, have been found in Nematodes, Annelids, Molluscs and in the arthropod, Drosophila
, despite earlier claims that nociceptors were absent in insects.
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.
Veterinary medicine uses, for actual or potential animal pain, the same analgesics and anesthetics as used in humans.
's simple nervous system. The report assumes that the violent reaction of lobsters to boiling water is a reflex to noxious stimuli.
However, review by the Scottish animal rights
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," 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.
A 2007 study at Queen's University, Belfast, suggested that crustaceans do feel pain. 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.
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. 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.
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. (However, the attenuated defensive response could originate from either the analgesic or sedative properties of morphine, or both.) These findings have been replicated for other invertebrate species, but similar data is not yet available for lobsters.
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s can experience pain
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
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.
In vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
s, endogenous opioid
Opioid
An opioid is a psychoactive chemical that works by binding to opioid receptors, which are found principally in the central and peripheral nervous system and the gastrointestinal tract...
s 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", some have interpreted their presence as an indication that crustaceans may be able to experience pain. Lobsters' opioids may "mediate pain in the same way" as in vertebrates.
Background
The idea that animals might not feel painPain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
as human beings feel it traces back to the 17th-century French philosopher, René Descartes
René Descartes
René Descartes ; was a French philosopher and writer who spent most of his adult life in the Dutch Republic. He has been dubbed the 'Father of Modern Philosophy', and much subsequent Western philosophy is a response to his writings, which are studied closely to this day...
, who argued that animals do not experience pain, because they lack consciousness
Consciousness
Consciousness is a term that refers to the relationship between the mind and the world with which it interacts. It has been defined as: subjectivity, awareness, the ability to experience or to feel, wakefulness, having a sense of selfhood, and the executive control system of the mind...
. Bernard Rollin
Bernard Rollin
Bernard E. Rollin is an American philosopher who specializes in animal rights and animal consciousness. He is a professor of philosophy, animal sciences, and biomedical sciences at Colorado State University....
of Colorado State University, the principal author of two U.S. federal laws regulating pain relief for animals, writes that researchers remained unsure into the 1980s as to whether animals experience pain, and veterinarians trained in the U.S. before 1989 were simply taught to ignore animal pain. 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. Carbone writes 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, some critics continue to question how reliably animal mental states can be determined.
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. Specialists currently believe that all vertebrates can feel pain, and that certain invertebrates, like the octopus, might too. Nociceptors, the neurones required for the sensation of pain, have been found in Nematodes, Annelids, Molluscs and in the arthropod, Drosophila
Drosophila
Drosophila is a genus of small flies, belonging to the family Drosophilidae, whose members are often called "fruit flies" or more appropriately pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species to linger around overripe or rotting fruit...
, despite earlier claims that nociceptors were absent in insects.
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.
Veterinary medicine uses, for actual or potential animal pain, the same analgesics and anesthetics as used in humans.
Research findings
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 lobsterLobster
Clawed lobsters comprise a family of large marine crustaceans. Highly prized as seafood, lobsters are economically important, and are often one of the most profitable commodities in coastal areas they populate.Though several groups of crustaceans are known as lobsters, the clawed lobsters are most...
's simple nervous system. The report assumes that the violent reaction of lobsters to boiling water is a reflex to noxious stimuli.
However, review by the Scottish animal rights
Animal rights
Animal rights, also known as animal liberation, is the idea that the most basic interests of non-human animals should be afforded the same consideration as the similar interests of human beings...
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," 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.
A 2007 study at Queen's University, Belfast, suggested that crustaceans do feel pain. In the experiment, when the antennae of prawns were rubbed with sodium hydroxide or acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...
, 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.
In a subsequent 2009 study, Elwood and Mirjam Appel showed that hermit crab
Hermit crab
Hermit crabs are decapod crustaceans of the superfamily Paguroidea. Most of the 1100 species possess an asymmetrical abdomen which is concealed in an empty gastropod shell that is carried around by the hermit crab.-Description:...
s make motivational tradeoffs between electric shocks and the quality of the shells they inhabit. 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.
Morphine
Morphine
Morphine is a potent opiate analgesic medication and is considered to be the prototypical opioid. It was first isolated in 1804 by Friedrich Sertürner, first distributed by same in 1817, and first commercially sold by Merck in 1827, which at the time was a single small chemists' shop. It was more...
, an analgesic, and naloxone
Naloxone
Naloxone is an opioid antagonist drug developed by Sankyo in the 1960s. Naloxone is a drug used to counter the effects of opiate overdose, for example heroin or morphine overdose. Naloxone is specifically used to counteract life-threatening depression of the central nervous system and respiratory...
, 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. (However, the attenuated defensive response could originate from either the analgesic or sedative properties of morphine, or both.) These findings have been replicated for other invertebrate species, but similar data is not yet available for lobsters.
See also
- Animal cognitionAnimal cognitionAnimal cognition is the title given to the study of the mental capacities of non-human animals. It has developed out of comparative psychology, but has also been strongly influenced by the approach of ethology, behavioral ecology, and evolutionary psychology...
- Emotion in animalsEmotion in animalsThere is no scientific consensus on emotion in animals, that is, what emotions certain species of animals, including humans, feel. The debate concerns primarily mammals and birds, although emotions have also been postulated for other vertebrates and even for some invertebrates.Animal lovers,...
- Pain in fishPain in fishThe presence of pain in an animal, or another human for that matter, cannot be known for sure, but the possibility that animals experience pain can be inferred through comparative brain physiology and physical and behavioral reactions...
- Pain in invertebratesPain in invertebratesPain in invertebrates is a problematic issue. Although there are numerous definitions of pain, almost all involve two key components. First, nociception is required. This is the ability to detect noxious stimuli which evokes a reflex response that moves the entire animal, or the affected part of...
- Animal cognitionAnimal cognitionAnimal cognition is the title given to the study of the mental capacities of non-human animals. It has developed out of comparative psychology, but has also been strongly influenced by the approach of ethology, behavioral ecology, and evolutionary psychology...
- Emotion in animalsEmotion in animalsThere is no scientific consensus on emotion in animals, that is, what emotions certain species of animals, including humans, feel. The debate concerns primarily mammals and birds, although emotions have also been postulated for other vertebrates and even for some invertebrates.Animal lovers,...
- Moral status of animals in the ancient worldMoral status of animals in the ancient worldThe 21st-century debates about animal welfare and animal rights can be traced back to the ancient world. The idea that the use of animals by humans—for food, clothing, entertainment, and as research subjects—is morally acceptable, springs mainly from two sources.First, there is the idea...
- Pain and suffering in laboratory animals
- SentienceSentienceSentience is the ability to feel, perceive or be conscious, or to have subjective experiences. Eighteenth century philosophers used the concept to distinguish the ability to think from the ability to feel . In modern western philosophy, sentience is the ability to have sensations or experiences...
Further reading
- Grandin, Temple and Deesing, Mark (2003 update) Distress in Animals: Is it Fear, Pain or Physical Stress? American Board of Veterinary Practitioners - Symposium 2002.
- Consider the Lobster Essay by David Foster WallaceDavid Foster WallaceDavid Foster Wallace was an American author of novels, essays, and short stories, and a professor at Pomona College in Claremont, California...
, published in GourmetGourmet (magazine)Gourmet magazine was a monthly publication of Condé Nast and the first U.S. magazine devoted to food and wine. Founded by Earle R. MacAusland and first published in 1941, Gourmet also covered "good living" on a wider scale....
, August 2004.