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Evidence for pain in decapod crustaceans
Abstract
Vast numbers of decapods are used in human food and currently subject to extreme treatments and there is concern that they might experience pain. If pain is indicated then a positive change in the care afforded to this group has the potential to produce a major advance in animal welfare. However, it is difficult to determine pain in animals. The vast majority of animal phyla have a nociceptive ability that enables them to detect potential or actual tissue damage and move away by a reflex response. In these cases there is no need to assume an unpleasant feeling that we call pain. However, various criteria have been proposed that might indicate pain rather than simple nociception. Here, with respect to decapod crustaceans, four such criteria are discussed: avoidance learning, physiological responses, protective motor reactions and motivational trade-offs. The evidence from various experiments indicates that all four criteria are fulfilled and the data are thus consistent with the idea of pain. The responses cannot be explained by nociception alone but, it is still difficult to state categorically that pain is experienced by decapods. However, the evidence is as strong for this group as it is for fish but the idea that fish experience pain has broader acceptance than does the idea of decapod pain. A taxonomic bias is evident in the evaluation of experimental data.
... Due to the inability of animals to verbally communicate their experiences to humans, and the fact that pain and nociception may occur in the absence of one another (Loeser and Melzack, 1999*;Shriver, 2006*;Wall, 1979*), the presence of an emotional component of pain in animals is often contested (Bermond, 2001*;Rose et al., 2014*). Nonetheless, pigs are recognised as sentient beings by law within the European Union (The Council of the European Union, 1997) and there is a general (though not complete) consensus within the scientific community that mounting evidence suggests animals, and mammals in particular, are capable of experiencing both nociception and pain, albeit not identically to humans, and only when certain physiological and behavioural criteria have been satisfied (Bateson, 1991*;Elwood, 2012*;Flecknell et al., 2011*;Gentle, 2011*;Mason and Mendl, 1993*;Shriver, 2006*;Sneddon et al., 2014*;Weary et al., 2006*). ...
... changes in heart rate, plasma corticosteroid concentrations, etc.) in response to noxious stimuli. These criteria are considered important evidence of the capacity to feel pain and are fulfilled by mammals, including pigs, and at least some species within several other taxa (Elwood, 2012*;Gieling et al., 2011*;Herskin and Di Giminiani, 2018 † ;Sneddon et al., 2014*;Viñuela-Fernández et al., 2011 † (see also sections 1.2.6-1.2.8)). In broad terms, behavioural indicators of pain include avoidance learning, trade-offs between responses to pain and other strongly motivated behaviours, self-stimulation of injury sites, protective / defensive behaviours, changes in sleeping, feeding, social, or explorative behaviours, vocalisations, appearance of abnormal behaviours, and behavioural changes in response to analgesics and attentional shifts (Bateson, 1991*;Dawkins, 1990*;Elwood, 2012*;Gentle, 2001;Herskin and Di Giminiani, 2018 † ;Ison et al., 2016*;Prunier et al., 2013*;Sneddon et al., 2014*;Weary et al., 2006*). ...
... These criteria are considered important evidence of the capacity to feel pain and are fulfilled by mammals, including pigs, and at least some species within several other taxa (Elwood, 2012*;Gieling et al., 2011*;Herskin and Di Giminiani, 2018 † ;Sneddon et al., 2014*;Viñuela-Fernández et al., 2011 † (see also sections 1.2.6-1.2.8)). In broad terms, behavioural indicators of pain include avoidance learning, trade-offs between responses to pain and other strongly motivated behaviours, self-stimulation of injury sites, protective / defensive behaviours, changes in sleeping, feeding, social, or explorative behaviours, vocalisations, appearance of abnormal behaviours, and behavioural changes in response to analgesics and attentional shifts (Bateson, 1991*;Dawkins, 1990*;Elwood, 2012*;Gentle, 2001;Herskin and Di Giminiani, 2018 † ;Ison et al., 2016*;Prunier et al., 2013*;Sneddon et al., 2014*;Weary et al., 2006*). ...
... Global use of decapod crustaceans (such as lobsters, prawns, crayfish and crabs) for human consumption is growing. Many billions of individuals are either wild caught or produced in aquaculture systems each year [1]. Historically, there has been little concern for the welfare of these animals because they were thought to have no ability to experience pain, and simply depended on nociceptive reflexes to escape from noxious stimuli [2]. ...
... Historically, there has been little concern for the welfare of these animals because they were thought to have no ability to experience pain, and simply depended on nociceptive reflexes to escape from noxious stimuli [2]. However, recent studies demonstrated that some responses of decapods cannot be explained as reflexes, and this opens the possibility that they feel pain and need to be protected [1][2][3][4]. By contrast, others [5][6][7][8] argue that the scientific literature on crustacean pain is weak and inconclusive, and there is no requirement to be concerned about their welfare. ...
... Boiling is a common slaughter method for decapods, but it appears to cause physiological shock and behavioural signs of aversion. For example, lobsters struggle violently for about two minutes after being placed in boiling water [1,4,68]. Lobsters and crabs thrash and try to escape, and shed their limbs, which may be signs of stress or pain (41). ...
Vast numbers of crustaceans are produced by aquaculture and caught in fisheries to meet the increasing demand for seafood and freshwater crustaceans. Simultaneously, the public is increasingly concerned about current methods employed in their handling and killing. Recent evidence has shown that decapod crustaceans probably have the capacity to suffer because they show responses consistent with pain and have a relatively complex cognitive capacity. For these reasons, they should receive protection. Despite the large numbers of crustaceans transported and slaughtered, legislation protecting their welfare, by using agreed, standardized methods, is lacking. We review various stunning and killing systems proposed for crustaceans, and assess welfare concerns. We suggest the use of methods least likely to cause suffering and call for the implementation of welfare guidelines covering the slaughter of these economically important animals.
... Recently, decapod crustaceans have become important models for biochemical, physiological, and ecological research [12][13][14][15][16], due to their biological characteristics and/or their convenience of collection/use. These characteristics include advanced circulatory hormones, immune systems, ease of culture, suitable size, individual traits, tolerance to handling, high fertility, relatively short generation time, and adaptability to a wide spectrum of environmental and nutritional conditions [17][18][19]. The crayfish, Procambarus clarkii, is used in physiological and immunological studies and as a biomarker in contaminated ecosystems [20][21][22][23][24][25][26][27][28]. ...
... Thus, decapods attend to the area of the body that received the noxious stimulation in a similar manner to that shown by mammals; (ii) Trade-offs between avoidance responses and other motivational requirements. Nociceptive reflexes should be the same irrespective of other motivational requirements [17,61]. If those responses vary according to other requirements, it would demonstrate central decision-making rather than reflex. ...
... (viii) Physiological responses. Pain activates various physiological responses, such as modifications in heart rate, respiration and/or hormonal levels [17,73,82,83], and these are generally regarded as stress responses. Stress is a biological response that an animal exhibits to cope with a threat to its homeostasis [84]. ...
Decapod crustaceans are widely used as experimental models, due to their biology, their sensitivity to pollutants and/or their convenience of collection and use. Decapods have been viewed as being non-sentient, and are not covered by current legislation from the European Parliament. However, recent studies suggest it is likely that they experience pain and may have the capacity to suffer. Accordingly, there is ethical concern regarding their continued use in research in the absence of protective measures. We argue that their welfare should be taken into account and included in ethical review processes that include the assessment of welfare and the minimization or alleviation of potential pain. We review the current use of these animals in research and the recent experiments that suggest sentience in this group. We also review recent changes in the views of scientists, veterinary scientists and animal charity groups, and their conclusion that these animals are likely to be sentient, and that changes in legislation are needed to protect them. A precautionary approach should be adopted to safeguard these animals from possible pain and suffering. Finally, we recommend that decapods be included in the European legislation concerning the welfare of animals used in experimentation. View Full-Text
... Experiments that examine the possibility of pain in decapods are important for understanding animal welfare. Decapods are fished in the wild, and reared in aquaculture systems, in vast numbers for human consumption, and, until recently, their treatment has not been shaped by welfare concerns [35,36]. The traditional view is that these animals respond to noxious stimuli only by reflex reactions and thus they have no capacity for pain or suffering [19]. ...
... Whilst we accept that there can be no absolute proof of pain in decapods the evidence that is consistent with sentience is sufficiently widespread within the taxon and of sufficient quality and variety that it is unreasonable to conclude that sentience is not possible [6,44]. Given that sentience is a possibility, protection for this group should be afforded, particularly in the food industry, in which billions of these animals are subject to extreme treatments, as well as in research [18,35]. ...
Simple Summary
The possibility of pain occurring in animals is often accepted if various criteria are fulfilled. These criteria include prolonged grooming or rubbing at the site of a wound or tissue damage, or other behaviour involving the site of damage. We also expect to see a reduction in such activities if a local anaesthetic is applied. Here, we report on an experiment that applied caustic soda, a known irritant in humans, to one eyestalk of the glass prawn. This caused immediate escape responses and then nipping and picking at the treated eyestalk rather than at the untreated eyestalk. Prior application of a local anaesthetic reduced the amount of directed behaviour. However, the local anaesthetic also appeared to be an irritant as it too caused immediate escape responses and directed behaviour to the eyestalk. The results provide further support to the idea that these animals can experience pain.
Abstract
Acceptance of the possibility of pain in animals usually requires that various criteria are fulfilled. One such criterion is that a noxious stimulus or wound would elicit directed rubbing or grooming at the site of the stimulus. There is also an expectation that local anaesthetics would reduce these responses to damage. These expectations have been fulfilled in decapod crustaceans but there has been criticism of a lack of replication. Here, we report an experiment on the effects of a noxious chemical, sodium hydroxide, applied to one eyestalk of the glass prawn. This caused an immediate escape tail-flick response. It then caused nipping and picking with the chelipeds at the treated eyestalk but much less so at the alternative eyestalk. Prior treatment with benzocaine also caused an immediate tail-flick and directed behaviour, suggesting that this agent is aversive. Subsequently, however, it reduced the directed behaviour caused by caustic soda. We thus demonstrated responses that are consistent with the idea of pain in decapod crustaceans.
... 7 Yet, whereas Godfrey-Smith wants to deny evaluative experience in insects, he grants it to crustaceans, where wound-tending has been shown (Birch et al. 2021). The work of Elwood and his collaborators Elwood et al. 2012) has been particular influential in this context, which -similarly to the early work by Cabanac -studied the evaluative trade-offs decapod crustaceans (shrimps, crabs, and the like) are engaged in. For instance, hermit crabs have shown that they are making state-based decisions on whether or not to leave their shell when receiving electric shocks, dependent upon both the predicted presence of predators and the shell value. ...
... 2). But there is no longer a debate on whether insects are capable of reinforcement learning (Allen et al. 2005;Elwood et al. 2012), and insect consciousness is starting to be taken as a serious possibility. Which forms of learning constitute the best kinds of evidence for consciousness, however, remains contested. ...
This goal of this thesis in the philosophy of nature is to move us closer towards a true biological science of consciousness in which the evolutionary origin, function, and phylogenetic diversity of consciousness are moved from the field’s periphery of investigations to its very centre. Rather than applying theories of consciousness built top-down on the human case to other animals, I argue that we require an evolutionary bottomup approach that begins with the very origins of subjective experience in order to make sense of the place of mind in nature. To achieve this goal, I introduce and defend the pathological complexity thesis as both a framework for the scientific investigation of consciousness and as a lifemind continuity thesis about the origins and function of consciousness.
... 10 Yet whereas Godfrey-Smith wants to deny evaluative experience in insects, he grants it to crustaceans, where wound tending has been firmly established. The work of Elwood and his collaborators (Appel and Elwood 2009;Elwood et al. 2012) has studied the evaluative trade-offs crustaceans are engaged in, particularly decapod crustaceans (shrimps, crabs, and the like). Hermit crabs have shown, for instance, that they are making state-based decisions on whether or not to leave their shell when receiving electric shocks, dependent upon both the predicted presence of predators and the shell value. ...
... A compelling line of evidence in this context is various kinds of learning, since they are commonly taken to increase our confidence in attributing evaluative experience. Also highlighted by Godfrey-Smith is reinforcement learning which has been shown in various insects (see Allen et al. 2005;Elwood et al. 2012) and is often drawn on in discussions of consciousness. Which forms of learning constitute the best kinds of evidence is, however, contested. ...
In order to develop a true biological science of consciousness, we have to remove humans from the center of reference and develop a bottom-up comparative study of animal minds, as Donald Griffin intended with his call for a “cognitive ethology.” In this article, I make use of the pathological complexity thesis (Veit 2022a, b, c) to show that we can firmly ground a comparative study of animal consciousness by drawing on the resources of state-based behavioral life history theory. By comparing the different life histories of gastropods and arthropods, we will be able to make better sense of the possible origins of consciousness and its function for organisms in their natural environments.
... 10 Yet whereas Godfrey-Smith wants to deny evaluative experience in insects, he grants it to crustaceans, where wound tending has been firmly established. The work of Elwood and his collaborators (Appel and Elwood 2009;Elwood et al. 2012) has studied the evaluative trade-offs crustaceans are engaged in, particularly decapod crustaceans (shrimps, crabs, and the like). Hermit crabs have shown, for instance, that they are making state-based decisions on whether or not to leave their shell when receiving electric shocks, dependent upon both the predicted presence of predators and the shell value. ...
... A compelling line of evidence in this context is various kinds of learning, since they are commonly taken to increase our confidence in attributing evaluative experience. Also highlighted by Godfrey-Smith is reinforcement learning which has been shown in various insects (see Allen et al. 2005;Elwood et al. 2012) and is often drawn on in discussions of consciousness. Which forms of learning constitute the best kinds of evidence is, however, contested. ...
In order to develop a true biological science of consciousness, we have to remove humans from the centre of reference and develop a bottom-up comparative study of animal minds as Donald Griffin intended with his call for a ‘cognitive ethology’. In this article, I make use of the pathological complexity thesis (Veit 2022a,c,b) to show that we can firmly ground a comparative study of animal consciousness by drawing on the resources of state-based behavioral life-history theory. By comparing the different life histories of gastropods and arthropods, we will be able to make better sense of the possible origins of consciousness and its function for organisms in their natural environments.
... Invertebrates are often treated in a way that indicates a low belief in their ability to feel pain and distress, and animal welfare legislation for invertebrates has also been limited, apart from the legislation for cephalopods (Horvath, Angeletti, Nascetti, & Carere, 2013;Sherwin, 2001). Yet, pain research indicates that there is some evidence for pain experience in decapod crustaceans, the taxon of invertebrates that includes the shrimp (Elwood, 2012). Research also suggests there is a range of cognitive capacities in invertebrates, including learning, memory, and communication, which may indicate that invertebrates are cognitively more complex than they have been credited for (Elwood, 2012;Grifffijin & Speck, 2004;Horvath et al., 2013;Sherwin, 2001). ...
... Yet, pain research indicates that there is some evidence for pain experience in decapod crustaceans, the taxon of invertebrates that includes the shrimp (Elwood, 2012). Research also suggests there is a range of cognitive capacities in invertebrates, including learning, memory, and communication, which may indicate that invertebrates are cognitively more complex than they have been credited for (Elwood, 2012;Grifffijin & Speck, 2004;Horvath et al., 2013;Sherwin, 2001). ...
Public attitudes toward the mind and status of animals are interrelated with the
ways in which they are treated in society. Therefore, it is important to understand
these attitudes, how they vary in society and what factors influence their
development. Additionally, how people make connections between meat and
animals influences their moral stance regarding the eating of animals. Thus, it is
useful to examine how cultural meanings of meat and its connection to animals are
constructed in everyday contexts. This thesis examines attitudes, perceptions and
meanings regarding farmed animals in Finnish society from the perspectives of
sociological animal studies. With this analysis, the thesis makes a contribution to
three key areas of discussion in sociological animal studies and in animal studies
generally: first, discussion on social determinants of attitudes toward animals;
second, people’s perceptions of animal mind and the ways in which these
perceptions vary in society and according to the categorisation of animals; and
finally, the cultural meanings associated with meat and with the meat–animal link.
The thesis is based on a mail survey with Finns (n = 1,824/1,890) and on five focus
groups with different consumer groups, comprising gastronomes, hunters, organic
consumers, rural women and supermarket customers (n = 39).
The first and second articles of the thesis examine the factors that associate with
Finnish attitudes to farmed animals and perceptions of their mental capacities
based on the survey of Finns. The first article suggests that there are important
social group differences in attitudes to farmed animals. Of social groups, gender
has the most robust link with these attitudes; on average, women express
consistently higher concern for farm animal wellbeing than men do. Additionally,
the article suggests that younger people and urban residents are more likely to
express greater concern for farmed animals than older people and rural residents.
The articles also show linkages between animal-related experiences and attitudes. Those who live or grew up on a farm with agricultural animals tend to express less
concern for farm animal wellbeing than those without a farming background.
Additionally, people who share their households with companion animals tend to
express greater concern for farmed animals and greater belief in their mental
capacities. The articles also provide evidence for positive association between
valuing social equality, concern for farmed animals and belief in their mental
capacities. In this way, the thesis provides empirical support for the suggestion that
attitudes to animal wellbeing and to human equality are linked.
The second article examines how Finns perceive the mind of different species. It
shows that phylogenetic and cultural categorisation of animals are linked to
people’s perceptions of their mind. Of mammals, people ascribe most mental
capacities to companion animals (dogs), followed by farmed animals (cows and
pigs) and wild animals categorised as threats or pests (wolves) and game (elk).
Apart from basic sentience, belief in the mental capacities of chickens is relatively
low. Additionally, Finns tend to ascribe minimal mind to salmons and shrimps.
Based on the focus groups, the third article examines the meanings Finnish
consumers associate with the use of animals for food. The article suggests that
consumers negotiate the meat–animal link in varying ways: some prefer to
dissociate meat from animals, while others appreciate products that visibly reflect
their animal origin. The article also highlights the ambiguities involved in placing
animals in the categories of companion and food. Earlier literature has suggested
that disconnecting meat from its animal origin is an important cultural process that
helps to maintain the meat-eating practice. However, this thesis demonstrates that
omnivores’ relationship to the meat–animal link is more complex as they may make
various kinds of connections between meat and animals. In the meat-eating logic
where the animal-origin of meat is less concealed, objectification of animals as
potential food is a central process that helps to uphold the meat-eating practice.
Overall, the thesis has contributed to developing a sociological approach to
studying animal-related attitudes and human–animal relations. It has generated
new insights into the social variation in attitudes to farmed animals and the
multifaceted ways in which consumers negotiate connections between meat and
animals. As a further development of the research field, the thesis highlights the
importance of incorporating into attitudinal research multispecies perspectives that
facilitate including animals more visibly as actors in research processes. There are
various avenues available to make attitudinal research less human-centric and take
it in more animal-inclusive directions.
Keywords: Animal Categorization, Animal Mind, Animal Welfare, Consumers, Cultural
Meanings, Farm Animals, Human–Animal Relationships, Meat, Public Attitudes,
Sociological Animal Studies
... The first signs of hominin consumption of cooked decapod crustaceans date back to the Middle Paleolithic [1]. Today, a large number of decapod crustaceans are consumed by humans; by some estimates, yearly landings approach 5 × 10 6 tons (~5% of global total fisheries production) and as many as 1.6 × 10 12 individuals [2][3][4]. The vast majority of decapods consumed by humans are slaughtered in large-scale industrial facilities, but small-scale exploitation and recreational harvesting remain important routes of generating side income or as leisure-time activities in many countries and cultures [3]. ...
The best practice for killing decapod crustaceans lacking a centralized ganglion has been debated for a century. Currently, there is a movement away from live boiling towards electrocution and mechanical splitting or spiking, which are efficient in the large commercial setting but may be unavailable and impractical for small decapods such as shrimp and prawn in the small-scale setting of, e.g., the household. Here, using carcasses of varying sizes of prawn, crayfish, lobster and green and brown crab, we used micro-CT imaging to measure surface area and sphericity in relation to body mass. Then, we measured heating profiles at the anterior ganglion and in the core of carcasses of the same species when exposed to standardized boiling regimes. We found a relationship with positive allometry between surface area and body mass for all species and a decrease in sphericity with mass. Heating times until proposed stunning (26 °C) and killing (44 °C) varied with body size and starting temperature and exceeded minutes for larger species. For a small species like prawn, times to stunning and killing by boiling are comparable to electrocution times and within the acceptable range compared to recreational killing of other sentient beings such as game mammals.
... Moreover, behavioural observations demonstrated that when shore crabs were exposed to acetic acid on their mouth and eyes, there was increased movement of the mouthparts and an attempt to hold down the eye treated with acetic acid [13]. Other behavioural studies have documented protective and escapist behaviours in response to potentially painful stimuli [12]. Concerns have been raised over the replicability of the responses to acetic acid stimulation in decapod crustaceans, but the results of the present study and those of other studies demonstrate consistent responses across different laboratories and species [3,13,14,38]. ...
Nociceptors detect damaging stimuli and send signals to the central nervous system (CNS) about potential injury, which can give rise to pain. Crustaceans, such as shore crabs, are widely used in science and aquaculture. Understanding whether they can experience pain is essential for improving their welfare. One key criterion for assessing pain is the presence of nociceptors. This study investigated the existence of nociceptors in shore crabs by examining the CNS response to two types of potentially noxious stimuli, i.e., mechanical and chemical or acetic acid. Using electrophysiological equipment, the crabs’ CNS activity was measured when different parts of its body, such as the soft tissues of the claws, antennae, and legs were stimulated. The results suggest that the crabs responded to both mechanical and chemical stimuli, indicating the existence of putative nociceptors in these areas. Interestingly, responses to physical stimuli were shorter and more intense than the chemical stimuli, which elicited a longer response. The antennae responded only to the chemical stimuli with no discernable response to touch. Although further research is needed to fully understand pain in crustaceans, this study provides important information on the perception of tissue damage in a crustacean.
... Its dramatic expansion, however, has also raised a number of concerns and objections, particularly regarding negative environmental impacts and its overall level of sustainability (Jiang et al., 2022;Wilding et al., 2018;Weitzman et al., 2019;GESAMP, 1991GESAMP, , 2008, and lately also with neglecting animal welfare (Elder, 2014;Birch, 2017;Brown and Dorey, 2019;Mather, 2019;Ellwood, 2012; although different perspectives can be observed: Browman et al., 2019;Jacquet et al., 2019;Seibel et al., 2020). ...
Marine aquaculture has grown enormously in recent decades, and with it the competition for space suitable for aquaculture. These developments have limited the areas available for aquaculture and, in some cases, have become a barrier to expansion. In response, aquaculture operations have moved further away from the coast. This development has created a need for clearer and more robust approaches to more comprehensively describe and secure sites for aquaculture. This article reviews the law governing the siting of aquaculture operations. In particular, it assesses the role of the widely used term “offshore” in the Law of the Sea to see if there are any legal aspects that need to be considered in moving towards the use of more specific concepts. It also aims to inform scientific discussions and political and administrative processes on the law governing the identification, description, and siting of aquaculture operations. This will hopefully contribute to more sustainable and less conflicted long-term aquaculture development.
... Third, since decapods demonstrate trait-biased dispersal, with bolder individuals outcompeting conspecifics, variation in boldness and activity may link to invasive success (Galib et al., 2022;Malmqvist, 2002). Furthermore, many billions of decapod crustaceans are harvested from wild fisheries and raised in aquaculture systems for human consumption annually (Elwood, 2012). Personality differences have been shown to predict trappability in decapods (Biro & Sampson, 2015;Moland et al., 2019) just as in vertebrates (Garamszegi et al., 2009;Vanden Broecke et al., 2021), and this differential trappability may exert selection pressures on behaviour in wild populations. ...
Personality variation, defined as among-individual differences in behaviour that are repeatable across time and context, is widely reported across animal taxa. From an evolutionary perspective, characterising the amount and structure of this variation is useful since differences among individuals are the raw material for adaptive be-havioural evolution. However, behavioural variation among individuals also has implications for more applied areas of evolution and ecology-from invasion biology to ecotoxicology and selective breeding in captive systems. Here, we investigate the structure of personality variation in the red cherry shrimp, Neocaridina heteropoda, a popular ornamental species that is readily kept and bred under laboratory conditions and is emerging as a decapod crustacean model across these fields, but for which basic biological, ecological and behavioural data are limited. Using two assays and a repeated measures approach, we quantify behaviours putatively indicative of shy-bold variation and test for sexual dimorphism and/or size-dependent behaviours (as predicted by some state-dependent models of personality). We find moderate-to-high behavioural repeatabilities in most traits. Although strong individual-level correlations across behaviours are consistent with a major personality axis underlying these observed traits, the multivariate structure of personality variation does not fully match a priori expectations of a shy-bold axis. This may reflect our ecological naivety with respect to what really constitutes bolder, more risk-prone, behaviour in this species. We find no evidence for sexual dimorphism and only weak support for size-dependent behaviour. Our study contributes to the growing literature describing behavioural variation in aquatic invertebrates. Furthermore, it lays a foundation for further studies harnessing the potential of this emerging model system. In particular, this existing behavioural variation could be functionally linked to life-history traits and invasive success and serve as a target of artificial selection or bioassays. It thus holds significant promise in applied research across ecotoxicology, aquaculture and invasion biology. K E Y W O R D S animal personality, behavioural syndrome, behavioural variation, boldness, cherry shrimp, decapod
... Shelters with higher structural complexity tend to be more attractive to shrimps as they provided more individualized spaces for animals to hide (Park et al., 2015). Decapod crustaceans are sensitive to stress (Elwood et al., 2009;Elwood, 2012;Magee and Elwood, 2013;Fossat et al., 2014), so creating a more pleasant environment by providing shelter could improve living conditions. Shrimp species show a variation in their activity pattern throughout the day, being more active at night. ...
Neocaridina davidi (Bouvier, 1904) is a shrimp commonly used in aquaculture throughout the world. It is an exotic species in several places. We investigated the preference of N. davidi for four types of shelter (rock, Vesicularia sp., Egeria sp., and wood) and its nictemeral activity variation. Individuals were divided into three experimental groups: males, non-ovigerous females, and ovigerous females. They were placed in tanks with the four shelter types and observed every 3 hours for 72 hours. Neocaridina davidi presented cryptic behavior with 82.1 ± 8.69% of individuals sheltering per observation. Sheltering was higher during the daytime (88.8 ±5.54%) than at nighttime (75.4 ± 5.53%). Vesicularia sp. was the most used shelter followed by wood. The least used shelter type was a rock. Swimming and walking were more frequently observed at nighttime, especially for ovigerous females. We have demonstrated the importance of providing shelter for the maintenance of N. davidi in tanks as well as its higher activity at nighttime.
... Recent studies demonstrated that some responses of decapods cannot be explained as refexes [17,61,184], opening the possibility that they can experience pain. Recently, there is a substantial consumer concern about the slaughter of certain decapod crustaceans-e.g., lobster and humane killing has been subject of recent studies [185]. ...
Despite the growing concern on animal welfare in crustacean farming, both from legislative bodies as well as the common public, studies on welfare are limited and transfer to routine farming is missing. While biocertification schemes such as the Aquaculture Stewardship Council (ASC) involve a welfare dimension, these dimensions cannot be communicated to the consumer in a scientifically sound manner. Animal welfare is recognized as integral part of sustainability due to the losses associated with bad animal welfare standards and is considered highly relevant by consumers around the world. On the other hand, increasing animal welfare is also required for the optimisation of aquaculture technology. Behaviour of the animals suggests that decapod crustaceans experience nociception and there are several indications of pain perception as well. Also, distress has rarely been evaluated under routine aquaculture conditions and markers for chronic stress detection need to be identified. Indeed, most work on welfare of crustaceans focuses on cellular, oxidative stress only. Here, a comprehensive assessment of chronic stress should be carried out to optimize rearing technology in nurseries, during ongrowing, harvesting, anesthesia, transportation, and humane slaughter in terms of a good aquaculture practise.
... Given functionally similar neuroanatomy and analogous behavioural responses to harm, few dispute that mammals and birds feel pain (Gentle, 1992). There is also growing expert consensus on pain in other animals, including the invertebrate cephalopod molluscs and decapod crustaceans Elwood, 2012). ...
... Being sentient also presupposes the possession of some ability to: 1. evaluate the actions of others towards himself and third parties; 2. to recall some of their own actions and their consequences, and 3. to assess the risks and benefits and to have feelings, and to have some degree of conscience. All vertebrates and some invertebrates such as cephalopods (octopus) and other molluscs, as well as crustaceans of the decapod order (lobsters, crabs...) meet this definition (Broom, 2014;Elwood, 2012). ...
Necessidade de alimentos! Conciliação entre a economia da produção de proteína sustentável e o tratamento ético dos animais: Um imperativo social de base científica.
Enquanto médico veterinário de formação tive oportunidade de trabalhar em diferentes áreas da profissão, e vão quase quarenta anos. De entre elas, a inspeção sanitária de produtos de origem animal, a medicina da produção e a medicina da conservação serão aquelas em que o papel destes profissionais será mais importante numa sociedade exigente e em marcada evolução. No meu caso, o exercício prático, o ensino e a investigação foram pontuando uma parte relevante da atividade profissional. Não obstante a apaixonante clínica de animais de companhia e a investigação em imunoalergologia, nunca perderia a perceção sobre o principal papel do médico veterinário na sociedade humanizada, o de promover a produção de alimentos de origem animal seguros, em quantidade suficiente e a custo acessível, num contexto mais lato, composto por quatro pilares fundamentais da responsabilidade dos Estados: alimentação, saúde, educação e justiça.
No século XX, excetuando alguns períodos de grande conturbação política e social, até à década de 1960 o modelo de progresso então em curso parecia solidamente imparável. Porém, a evolução a todos os níveis exponencial, observada no planeta, encaminhava-se para uma preocupante insustentabilidade, comprometedora da própria sobrevivência de inúmeras espécies. Ainda na segunda metade do século XX, tal situação começava já a virar progressivamente o foco da consciência social no sentido da necessidade de travar as gravosas e previsivelmente trágicas modificações climáticas associadas. O modelo de desenvolvimento tecnológico em curso não cabia já na nossa Terra. Havia-se chegado à lua, mas, apesar do turismo espacial ser já uma realidade, mesmo que exclusivista, uma possível colonização em massa do espaço afigura-se mais complicada. Certo é que teremos já ultrapassado o ponto de viragem, em termos de impacto ambiental, do modelo de progresso saído da revolução industrial. É como se o planeta começasse a suar mais do que a água que consegue beber, desidratando-se perigosamente. Começa a ser evidente a necessidade cada vez mais urgente de inverter o rumo, perante uma natureza em asfixia. Especialistas mundiais vêm-se reunindo para discutir este cada vez mais assustador problema. A opinião pública começa a reparar nele, preocupando-se, ainda que a sociedade, rendida à volúpia consumista, não permita, para já, o necessário grau de cidadania aderente. Em todo o caso, e felizmente, as questões ambientais começam a chamar a atenção real de líderes políticos um pouco por todo o mundo e os resultados, não sendo tão rápidos quanto desejável para garantir já o salvamento do planeta doente, vêm, pelo menos, colocando aquelas questões na agenda política internacional, de forma incontornável, vincando a preocupação dos cidadãos. Com as sucessivas Conferências das Nações Unidas sobre Alterações Climáticas (COP) lá vamos seguindo de COP em COP e, mesmo com as fraturantes ausências de importantes poluidores, o caminho vai-se fazendo. Diz-se que água mole em pedra dura, tanto bate até que fura – temos, ainda, uma nesga de esperança neste mundo global, entre pandemias supra-bíblicas e a biologia molecular mais state of the art. Como resumia Frans Timmermans, vice-presidente da Comissão Europeia e representante europeu nas negociações da COP26, relativamente aos resultados alcançados: “O perfeito é inimigo do bom”. Que o tempo gasto não tenha sido tempo perdido, como onomatopeicamente expressava a ativista sueca Greta Thunberg: “Blá, blá, blá”. É o que todos nós cidadãos, esperamos.
Para poder ultrapassar os exigentes desafios que temos pela frente precisamos focar o extraordinário potencial científico, que não para de crescer, no desenvolvimento de um modelo tecnológico de produção alimentar seguro, acessível e de distribuição justa. O conhecimento científico e tecnológico deve permitir à população mundial um equilíbrio incontornavelmente democrático, respeitando também os nossos parceiros na natureza, de forma a mantê-la sã e sustentável para as gerações vindouras. Só assim garantiremos a nossa própria sobrevivência, como parte integrante do ecossistema terrestre. Não nos considerarmos pares dos outros seres vivos, posicionando-nos arrogantemente como superiores, resulta no que está à vista de todos. Neste contexto, afigura-se especialmente importante que a humanidade comece, de forma inequívoca, por respeitar todos os que, de forma senciente, são capazes de sentir e de sofrer, física e emocionalmente. Também neste aspeto a ciência deve ser ouvida, sendo consideravelmente preocupante observar que, após a extraordinária evolução do conhecimento científico, grandes massas populacionais continuem a fazer opções à sua margem, promovendo lideranças políticas flutuantes entre a ignorância e o cinismo, com graves consequências para todos os habitantes de um planeta que, do espaço, de onde o conjunto que somos se pode observar, não apresenta fronteiras. A prossecução de objetivos tão necessariamente ambiciosos, relacionados com a nossa própria sobrevivência planetária, requer uma estabilidade decisória que permita um desenvolvimento económico equilibrado e sustentável, associado a uma redistribuição da riqueza. É isso a que chamamos progresso, paz social e democracia. Trata-se, verdadeiramente, de uma responsabilidade dos Estados, mas nem todos a demonstram, levando, perante a falta de acesso a uma vida digna, tantas vezes sem a elementar expectativa de sobrevivência, a que “os pobres assaltem a casa dos ricos”. É o triste espetáculo que entra diariamente pelas nossas casas dentro, quando a ausência de paz social, e mesmo de recursos alimentares, promove ondas migratórias vindas de sul, rumando em direção à Europa e à América do Norte. Este espetáculo desumano, e que conta também com muros e arame farpado como atores, não é compatível com os princípios democráticos, exigindo consensos internacionalmente alargados. Esse objetivo deve também manter-se na agenda política internacional, devendo mesmo ser um dos temas fulcrais das políticas públicas transnacionais. Curiosamente, do espaço não se vê o arame farpado!
Neste número especial do Jornal Português de Políticas Públicas, dedicado à produção alimentar sustentável, às alterações climáticas e ao tratamento ético dos nossos maiores fornecedores de proteína, os animais, é com apreciável satisfação que pudemos contar com vários nomes de reconhecido prestígio naqueles domínios. Carlos Fiolhais, professor universitário, físico, ensaísta e um extraordinário divulgador de ciência, expõe-nos com uma lucidez clarificadora aspetos essenciais associados às alterações climáticas e à produção de alimentos. Afinal, a agricultura industrializada não é a mãe de todos os males, mas, no global, aqueles tendem claramente a agravar-se se mudanças cientificamente baseadas não se fizerem. Os factos científicos aqui desmontados e explicados com extraordinária clareza permitem-nos compreender melhor a dimensão inerente a estes temas. Manuel Chaveiro Soares, professor universitário, agrónomo, administrador e empresário de sucesso é alguém que muito admiro, pela extraordinária visão científica que mantem da sociedade, a qual lhe permite manter na crista do sucesso empresarial as atividades que empreende. Apresenta-nos factos incontornáveis do desenvolvimento biotecnológico, que, com a sua repercussão a nível farmacêutico e da produção alimentar, sem contornar a questão do impacto ambiental, nos mostra como foi possível sermos hoje mais saudáveis, sentirmo-nos mais seguros e, talvez mesmo, mais felizes. Fernando Bernardo, professor universitário, médico veterinário e ex-Diretor Geral de Alimentação e Veterinária foi, desde que o conheci como meu professor, alguém cuja elevação me captou a atenção e marcou positivamente. Como poucos, recorrendo aos seus conhecimentos científicos e do terreno, apresenta-nos o panorama atual da produção alimentar em Portugal, em termos de sustentabilidade e, de forma integrada, em termos sociais, económicos, culturais e sanitários. Trata-se, pois, de uma perspetiva a levar muito em conta, em termos de política agroalimentar. Christiane Souza, Flávio Vieites, Antônio Castro, Luís Martins e Cristina Ribeiro de Lima são também todos académicos, com estreita ligação ao terreno e um denominador comum, a experiência diferenciada no domínio da produção avícola de elevada eficiência. Experiências diferentes, mas complementares, permitiram a presente visão da produção avícola, nas suas diferentes vocações, em termos da extraordinária evolução tecnológica, do impacto socioeconómico e da dinâmica territorial, recorrendo ao exemplo de uma grande potência como o Brasil. Demonstram, acima de tudo, como a produção de proteína alimentar de alto valor biológico é possível, de forma muito eficiente, ou seja, com contido impacto ambiental. José Afonso de Almeida, professor universitário, médico veterinário, cedo demonstrou uma capacidade singular de gestão académica, cuja competência o levaria a ocupar diferentes lugares cimeiros da organização universitária. Sem nunca perder o gosto por ensinar, tornou-se para muitos de nós uma referência de pensamento. O seu contributo para este número não podia ser mais relevante e inquietante. De facto, a arena moral em que colocamos os outros animais, sejam eles de companhia, trabalho, desporto, lazer ou mesmo de comer e vestir, é algo que colide frequentemente com os valores modernos que consideramos humanistas e cívicos. Mas é preciso conhecer bem o histórico e a natureza animal, nas suas várias facetas, para melhor enquadrar a dimensão da questão. É isso que, de forma brilhante, aqui nos oferece.
... Being sentient also presupposes the possession of some ability to: 1. evaluate the actions of others towards himself and third parties; 2. to recall some of their own actions and their consequences, and 3. to assess the risks and benefits and to have feelings, and to have some degree of conscience. All vertebrates and some invertebrates such as cephalopods (octopus) and other molluscs, as well as crustaceans of the decapod order (lobsters, crabs...) meet this definition (Broom, 2014;Elwood, 2012). ...
Technological, Socioeconomic and Territorial Dynamics of Poultry Sector in Brazil – An Example of Efficient High Quality Protein Production.
Poultry farming is an important segment of Brazilian agribusiness, generating jobs and income, as well as providing important products to the population. This study aimed at understanding the technological, socioeconomic and territorial dynamics of poultry and egg production in Brazil. The methodology employed was the bibliographic survey with information obtained from documental sources. Numerous changes have occurred in beef and egg laying aviculture; equipment and installations were altered with the advent of technology, which provided favorable conditions for the avian husbandry, altered zootechnical indices allowed the promotion of better animal welfare, improved productivity and, consequently, the economic results of this activity. It was found that Brazilian companies in the poultry sector are mostly located in the southern, southeastern and central-western regions, with the predominance of the integration system. Brazilian small and medium producers have different characteristics and demands regarding social, economic, educational and cultural conditions. Thus, technical assistance and rural extension assumes an important role. The complexity of poultry agro-industrial system has a strong impact on the economic dynamics of the regions in which this activity is installed, with a clear reflex on human developmental indicators.
Keywords: Poultry industry, rural development, technologies.
JEL classification: O30, O32, O33, Q00, Q16.
... Barring the acceptance of particular theories of consciousness, such as panpsychism, in which sentience is an intrinsic property of certain natural phenomena rather than an evolved function.24 Researchers attempting to make progress on this issue include;(Barr et al., 2008;Carder 2017;Diggles 2019;Eisemann et al., 1984;Elwood 2011Elwood , 2012Klein and Barron 2016;Lockwood 1987;Puri and Faulkes 2010;Sømme 2005).Content courtesy of Springer Nature, terms of use apply. Rights reserved. ...
Animal welfare science and ecology are both generally concerned with the lives of animals, however they differ in their objectives and scope; the former studies the welfare of animals considered ‘domestic’ and under the domain of humans, while the latter studies wild animals with respect to ecological processes. Each of these approaches addresses certain aspects of the lives of animals living in the world though neither, we argue, tells us important information about the welfare of wild animals. This paper argues for the development of a new scientific discipline ‘welfare biology’ to address these issues and more, given the deficiencies of pre-existing life science disciplines to research the subject. Welfare biology is the study of the welfare of all living beings who have a welfare, with a value orientation toward promoting that welfare, regardless of the beings’ situation or relationship to humans and our activities.
... An underlying assumption of the entire framework is that when sentient animals are not protected by animal welfare legislation, they are put at greatly increased risk of serious, negative welfare outcomes. In the case of decapods, the case can be easily made by pointing to practices widespread in the food and fishing industries such as live boiling, live carving, and de-clawing -practices that, if inflicted on a vertebrate, would violate even the most minimal animal welfare standards (Elwood 2012;Roth and Grimsbø 2016). ...
... Live bait, including fish, cephalopods, and crustaceans, can significantly compromise the welfare of these animals (Davie & Kopf, 2006). The evidence that cephalopods and crustaceans feel pain is as strong as it is for fish (Elwood, 2012;Ponte, Andrews, Galligioni, Pereira, & Fiorito, 2019). Poor welfare of live bait can occur from transporting animals, their holding conditions and hooking injuries. ...
... Markers of traditional pain perception include the presence of endogenous opioids, responsiveness to anaesthetics and analgesics, grooming of injured body parts, a reduction in grooming behavior under analgesia, and 'motivational tradeoffs' such as when hermit crabs are willing to withstand a mild electric shock in order to obtain a more desirable shell (Elwood 2011(Elwood /2012. Shrimps groom their antennae after sustaining an injury -a behavior reduced when given an analgesic (Barr et al. 2008). ...
Invertebrate animals are frequently lumped into a single category and denied welfare protections despite their considerable cognitive, behavioral, and evolutionary diversity. Some ethical and policy inroads have been made for cephalopod molluscs and crustaceans, but the vast
majority of arthropods, including the insects, remain excluded from moral consideration. We argue that this exclusion is unwarranted given the existing evidence. Anachronistic readings of evolution, which view invertebrates as lower in the scala naturae, continue to influence public policy and common morality. The assumption that small brains are unlikely to support cognition or sentience likewise persists, despite growing evidence that arthropods have converged on cognitive functions
comparable to those found in vertebrates. The exclusion of invertebrates is also motivated by cognitive-affective biases that covertly influence moral judgment, as well as a flawed balancing of scientific uncertainty against moral risk. All these factors shape moral attitudes toward basal
vertebrates too, but they are particularly acute in the arthropod context. Moral consistency dictates that the same standards of evidence and risk management that justify policy protections for vertebrates also support extending moral consideration to certain invertebrates. Moving beyond a
vertebrate-centered conception of welfare can also clarify foundational moral concepts in their own right.
... Positive and negative feelings --pleasure, pain, fear, anxiety etc. --are important adaptive mechanisms that have evolved in a range of animal groups. A pain system can be fully functional with a brain structure different from that of a mammal; such systems are described for fish, cephalopods and decapod crustacea (Mather 2013(Mather , 2020Broom 2016;Elwood 2012Elwood , 2020 as well as for mammals and birds. Several studies of gastropod molluscs and of insects such as ants and bees indicate the possibility of a pain system with complex brain components (Broom 2013(Broom , 2014. ...
Sentience is not confined to animals with large or human-like brains. Moral standing should be accorded to all animals, not just vertebrates: invertebrates deserve moral consideration too. Carefully defining the relevant terms can help clarify the relationship between sentience and welfare. All animals have welfare but humans accord more protection to sentient animals. Humans should be less human-centred.
... There is no agreement about whether insects are conscious or not, and, more fundamentally, no agreement on a methodology that could settle the issue. The same problem arises in other disputed cases of consciousness in invertebrates: cephalopod molluscs (Godfrey-Smith, 2016;Mather, 2007Mather, , 2019 and decapod crustaceans (Birch, 2017;Elwood, 2012). Though my focus in this article is on evidence from invertebrates, debates of a very similar character occur in relation to fish (see Key, 2016 and the 46 associated commentaries). ...
There is no agreement on whether any invertebrates are conscious and no agreement on a methodology that could settle the issue. How can the debate move forward? I distinguish three broad types of approach: theory-heavy, theory-neutral and theory-light. Theory-heavy and theory-neutral approaches face serious problems, motivating a middle path: the theory-light approach. At the core of the theory-light approach is a minimal commitment about the relation between phenomenal consciousness and cognition that is compatible with many specific theories of consciousness: the hypothesis that phenomenally conscious perception of a stimulus facilitates, relative to unconscious perception, a cluster of cognitive abilities in relation to that stimulus. This “facilitation hypothesis” can productively guide inquiry into invertebrate consciousness. What is needed? At this stage, not more theory, and not more undirected data gathering. What is needed is a systematic search for consciousness-linked cognitive abilities, their relationships to each other, and their sensitivity to masking.
... molting and copulation, incubation of eggs by females or stress caused by e.g. pain or changes in environmental conditions (Williams 1982;Norman & Jones 1992;Freie 1996;Elwood 2012). It should also be considered that the analyzed specimens were collected from fishing nets, where they could digest the food consumed earlier or could have no access to food. ...
The feeding ecology of the Chinese mitten crab Eriocheir sinensis was studied by analyzing the stomach fullness and its content with regard to sex, size and brackish water habitats occurring on the coast of the Baltic Sea (Gulf of Gdańsk and Vistula Lagoon, Poland) and the Atlantic (Tagus Estuary, Portugal). The presented results show that neither the site, sex (except the Gulf of Gdańsk) nor the size of an individual had a significant (p > 0.05) effect on the stomach fullness of E. sinensis. However, the type of food consumed was significantly (p < 0.05) correlated with the inhabited locality. The stomachs of crabs contained the remains of animal and plant origin, as well as detritus. The remains of animals (Bivalvia, Amphipoda, Gastropoda and Polychaeta) were more frequently found in the crabs from the Gulf of Gdańsk, while the remains of plants (Tracheophyta, Chlorophyta) were most often found in the stomachs of crabs from the Vistula Lagoon and the Tagus Estuary. Detritus was found only in the Gulf of Gdańsk and the Vistula Lagoon. Research indicates that the feeding ecology of omnivore E. sinensis is habitat specific, which should be taken into account when assessing the risk associated with this invasive species.
... For example, a feeling is a brain activity that involves at least perceptual awareness; it is associated with a life-regulating system and recognizable by the individual when it recurs, and it may change behavior or act as a reinforcer in learning. Feelings, such as pain and fear, are now thought to be widespread in mammals, birds, fish, cephalopods and some other molluscs, and in decapod crustacea (Elwood, 2012;Broom, 2013;Mather, 2013). ...
Sentience means having the capacity to have feelings. This requires a level of awareness and cognitive ability. There is evidence for sophisticated cognitive concepts and for both positive and negative feelings in a wide range of nonhuman animals. The abilities necessary for sentience appear at a certain stage in humans, as in other species, and brain damage can result in those abilities being lost so not all humans are sentient. Sentient animals include fish and other vertebrates, as well as some molluscs and decapod crustaceans. Most people today consider that their moral obligations extend to many animal species. Moral decisions about abortion, euthanasia, and the various ways we protect animals should take into account the research findings about sentience.
... haps unsurprising that dialogue surrounding ethical concerns about improving invertebrate ethics often hinges on cephalopods. Current concerns about their care can be seen in recent petitions on banning live consumption of octopus in US restaurants, one of which gained over 47,000 signatures (Wolverton, 2019).However, in the light of research on lobster pain perception(Barr et al., 2008;Elwood, 2012), there has also been a flurry of petitions in multiple countries, demanding a range of tighter ethical controls over treatment of crustaceans. In the UK, a recent petition demanding the British Government include lobsters and crabs under the Animal Welfare Act, exceeded 41,000 signatures (Crustacean Compassion, 2018). ...
Invertebrate study systems are cornerstones of biological and biomedical research, providing key insights into fields from genetics to behavioural ecology. Despite the widespread use of invertebrates in research, there are very few ethical guidelines surrounding their use.
Focussing on two ethical considerations faced during invertebrate studies—collecting methods and euthanasia—we make recommendations for integrating principles of vertebrate research into invertebrate research practice.
We argue, given emerging research on invertebrate cognition and shifting public perception on the use of invertebrates in research, it is vital that the scientific community revisits the ethics of invertebrate use in research.
Without careful consideration and development of the ethics surrounding the use of invertebrates by the scientific community, there is a danger of losing public support. It is imperative that the public understand the significance of research that uses invertebrates and that scientists demonstrate their ethical treatment of their experimental subjects.
... Lobster was chosen in order to explore the effect of giving information about the killing of an animal and because we suspected that, in line with the Liao and Meskin (2018) prediction, positive ethical information with a trace might have a negative effect on expectations in this case. Several studies indicate that crustaceans are able to feel pain (Elwood et al., 2009;Elwood, 2012) leading to controversy about the way in which lobsters are killed before cooking. For lobster we created only positive vignettes (control, positive/no trace -sustainable, positive/trace -humanely killed). ...
It has been suggested that information about ethically relevant factors in production can affect both the expectation and experience of foods. However, evidence on these issues is inconsistent. We begin by discussing recent philosophical work on the interaction of ethical and aesthetic values in the domain of food, which is inspired by a similar debate about art. Some philosophers have suggested that ethical factors in production that leave a ‘trace’ on a product, i.e., make a perceivable difference to it, will affect the aesthetic quality of the food. There has also been the suggestion that these sorts of ethical/aesthetic interactions may vary across different kinds of food. In two studies we examined the expected experience and the actual experience of eating various foods, when participants had been given ethically relevant information about those foods. We examined people’s ethical values and the effect that had on the ratings. We found strong evidence to suggest that ethically relevant information affects expected experience of food and that the valence of the information is a significant factor. We found an effect of ethical values on expectations of food. Most notably, we found evidence that suggests that ‘trace’ may be a relevant factor mediating the effect of ethically relevant information on expectations and experience of food. Future research should further explore the factor of trace, look at the effect of ethical information in a wider range of foods, and investigate these phenomena in distinct populations.
... Fish appear to have the ability to experience negative states such as pain and stress in a way analogous to that experienced by other vertebrates, and the physiological changes that occur in response to acute and chronic stress in fish are similar to those described for mammals (Braithwaite & Ebbesson, 2014;Brown, 2016). Experimental studies on hermit crabs (Elwood & Appel, 2009), prawns (Barr, Laming, Dick, & Elwood, 2007), crabs, and lobsters (Elwood, 2012) reveal behavior consistent with pain such as avoidance learning, physiological responses, and protective motor reactions. Reptiles display characteristic responses to painful stimulation that are reduced by analgesia, and like amphibians possess an endogenous opioid system involved in pain mechanisms found in mammals (Sneddon, Elwood, Adamo, & Leach, 2014). ...
Despite the widespread belief among the public and an increasing number of law enforcement personnel that individuals who harm animals often harm other people, the subject of animal maltreatment has received little attention from behavioral scientists. Advances in comparative neuroanatomy have highlighted the ability of animals to feel physical and emotional pain, including complex psychological reactions to traumatic events. These advances, and recent studies (however sparse) that support the notion that perpetrators of crimes against animals often commit other crimes, have arguably created an ethical and practical imperative for behavioral scientists to undertake a serious examination of animal maltreatment and potential mechanisms for responding to it. In addition, the close and complex relationships many Americans have with animals and the advancements in animal protection law in the past two decades necessitate expertise on the part of forensic psychologists and psychiatrists, who will increasingly be called upon to evaluate animal maltreatment offenders and consult on related policy and legislation.
The evolutionary emergence of consciousness is a research topic that has been attracting increasing attention in recent years. In a brief span of time, the debate surrounding various models in this area is driving the development of an increasingly specific research agenda. In this article, we examine the main available models of emergence. All the models we discuss assume, with varying degrees of caution, that consciousness emerged through convergent evolution in three distinct phyla within the animal kingdom. Nevertheless, they provide a unified account that aims to comprehensively cover all independent tokens of emergence. After analyzing the suitability of this unifying strategy through the lens of contemporary evolutionary theory, we recommend adopting a token-by-token, phylum-by-phylum approach. At this point, we emphasize the advantage of accumulated comparative knowledge regarding vertebrate evolution, advocating for an interoceptive view of the emergence of consciousness in vertebrates.
My account of neoclassical choice theory, NCT, differs from yours. If not, it is not worth pondering. My perspective is broad, including risk, uncertainty, and beliefs. Everything you care about is included, plus all your constraints. Individual plants, machines, and animals might be economici. Humans? This chapter emphasizes the assumptions and definitions: standard ones are deconstructed, and implicit ones are identified. They and what follows from their different subsets is the focus of this chapter, not judgment.
The entomology literature has historically suggested insects cannot feel pain, leading to their exclusion from ethical debates and animal welfare legislation. However, there may be more neural and cognitive/behavioural evidence for pain in insects than previously considered. We use Birch et al. 's (2021) eight criteria for sentience to critically evaluate the evidence for pain in insects. We assess six orders (Blattodea, Coleoptera, Diptera, Hymenoptera, Lepidoptera, and Orthoptera) in at least two life stages (adult and first instar juveniles, as well as other instars where relevant data are found). Other insect orders have not received enough research effort to be evaluated. According to the Birch et al. framework, adult Diptera (flies and mosquitoes) and Blattodea (cockroaches and termites) satisfy six criteria, constituting strong evidence for pain. Adults of the remaining orders (except Coleoptera, beetles) and some juveniles (Blattodea and Diptera, as well as last instar Lepidoptera [butterflies and moths]) satisfy 3–4 criteria, or “substantial evidence for pain”. We found no good evidence that any insects failed a criterion. However, there were significant evidence gaps, particularly for juveniles, highlighting the importance of more research on insect pain. We conclude by considering the ethical implications of our findings where insects are managed in wild, farmed, and research contexts.
Octopuses, crabs and lobsters are probably sentient, yet their welfare needs are poorly protected in the food system. Upholding animal welfare in the seafood industry presents challenges, and more research is needed to address humane capture, housing and slaughter.
My recent review examined the complex and intimate relationship between hermit crabs and the empty gastropod shells upon which they depend for survival. Because shells come with costs as well as benefits, the crabs are highly selective about which ones they prefer to occupy. Thus, a new shell is investigated and the information that is gathered appears to be compared with their existing shell before a decision is made. This is often prolonged and complex. Crabs also fight for shells and again the information that is gathered and used to inform fight decisions is complex. In my review, I consider these and other situations with reference to the possibility of sentience (including awareness). The excellent commentary from Mark Briffa expands on aspects of sentience and invokes the use of Lloyd Morgan's Canon to avoid suggesting complex abilities when simpler explanations would suffice. I agree with this approach. However, I also suggest that when simpler explanations appear not to explain the data, then it is reasonable to consider if more complex mental abilities might be used. I also like Briffa's suggestion that the use of an apparently higher mental faculty might result in a mechanism that is simpler than a large number of apparently simple decisions used to make complex decisions.
Homeostasis is the maintenance by an animal of a relatively constant state, which in turn increases efficiency of physiological processes. From a behavioral perspective, homeostasis can be as simple as moving back and forth between sun and shade to keep body temperature constant. Assessment and behavioral response to internal state, such as hunger, thirst, and searching for mates are all homeostatic processes, many of which are regulated by feedback loops. Adjusting time investment in activities—time budgeting—allows animals to accomplish the various tasks required for survival. Biological clocks help animals to adjust their homeostatic activity. Topics such as sleep, fear, and pain fall within the general realm of this topic as well. Within a species, animals may vary in their responses to a particular set of circumstances; this variation is an expression of personality, or behavioral syndrome. Oftentimes, behavioral syndrome is expressed as a shy to bold continuum, with some animals in a population behaving more boldly than others. Homeostasis is the key to understanding why an animal performs a specific behavior at a given time.
This study evaluated the effects of continuous exposure to the essential oil of Cymbopogon citratus (EOC) on behavioural and biochemical parameters in shrimp Litopenaeus vannamei. Adult shrimp were randomly placed in aquaria and divided into the following groups: control (pure seawater), ethanol (360 μl L−1 of ethanol) and 5 or 10 μl L−1 EOC for 6 h. Shrimp movements were recorded using a camera for 5 min at the following timepoints: 0, 1, 2, 4 and 6 h of exposure. Light sedation and behavioural changes were observed in shrimp in the 10 μl L−1 EOC group. The total antioxidant capacity against peroxyl radicals (ACAP) in the gills and hepatopancreas of shrimp exposed to 10 µl L−1 EOC was higher than control, whereas, in the muscle, it was lower in those exposed to 5 µl L−1 EOC. In the gills and hepatopancreas, reduced glutathione (GSH) was increased in the control group. Sulphhydryl groups associated with protein (P‐SH) were decreased in the gills of shrimp exposed to 10 μl L−1 EOC. Thiobarbituric acid reactive substance levels, indicative of lipid peroxidation, were higher in the gills and hepatopancreas of shrimp exposed to ethanol, which indicates ROS formation. It is concluded that EOC reduced the swimming behaviour of L. vannamei and improved their tolerance with up to 6 h of exposure.
Traditional approaches in comparative cognition have a long history of focusing on a narrow range of vertebrate species. However, in recent years the range of model species has expanded. Despite this development, invertebrate taxa are still largely neglected in comparative cognition, which limits our ability to locate the origins of cognitive traits. The time has come to rethink cognition and develop a more comprehensive understanding of cognitive evolution by expanding comparative analyses to include a diverse range of invertebrate taxa. In this review, we contend that cephalopods are suitable ambassadors for rethinking cognition. Cephalopods have large complex brains, exhibit sophisticated behavioral traits, and increasing evidence suggests that they possess complex cognitive abilities once thought to be unique to large-brained vertebrates. Comparing cephalopods with vertebrates, whose cognition has evolved independently, provides prominent opportunities to circumvent current limitations in comparative cognition that have arisen from traditional vertebrate comparisons. Increased efforts in investigating the cognitive abilities of cephalopods have also led to important welfare-related improvements. These large-brained molluscs are paving the way for a more inclusive approach to investigating cognitive evolution that we hope will extend to other invertebrate taxa.
Les parasites à transmission trophique socrustacés amphipodent connus pour les changements phénotypiques qu’ils induisent chez leurs hôtes. Ces changements sont supposés favoriser la transmission des parasites vers un hôte définitif à travers la prédation de l’hôte intermédiaire. Ce phénomène de « manipulation parasitaire » a longtemps été vu comme un trait adaptatif des parasites. La manipulation reposant sur des interactions proie-prédateur, il est nécessaire de comprendre comment les comportements antiprédateur sont modulés par des facteurs exogènes (pression de prédation) et endogènes (infection parasitaire, état émotionnel, …) aux individus. Au cours de cette thèse, nous avons tenté d'approfondir la compréhension de ce phénomène, chez les s, en répondant à plusieurs questions : (1) quelle est l'étendue de la multi-dimensionnalité de la manipulation parasitaire par les Acanthocéphales, quantifiée au travers d'une méta-analyse ; (2) l'amplitude des changements de comportements antiprédateur varie-t-elle selon le contexte local de prédation ? ; (3) les comportements antiprédateur présentent-ils une flexibilité en lien avec le contexte local de prédation ? ; (4) le parasite "exploite" t-il la flexibilité comportementale des gammares sains, notamment en lien avec leur régulation émotionnelle de type anxiété ?. Au niveau inter-spécifique à l'échelle du phylum des Acanthocéphales, nous avons mis en évidence une altération marquée des comportements en lien avec la défense antiprédateur des hôtes (changement de micro-habitat, protection et réponse à des stimuli). Au niveau du couple hôte-parasite Gammarus fossarum, Pomphorhynchus tereticollis, nous avons montré que l’intensité des changements de comportements antiprédateur induit par l'infection (utilisation de refuge, phototaxie) présentait une variabilité inter-populationnelle, en lien avec le risque de prédation : la manipulation semble d’autant plus forte que la pression de prédation locale, i.e. les opportunités de transmission, est faible. Chez les individus sains, nous avons mis en évidence, par une approche corrélationnelle, une variabilité inter-populationnelle de l’intensité des comportements anti-prédateur en lien avec le risque local de prédation, et la densité de gammares conspéficiques. Nous avons également montré une flexibilité de la réponse au stimulus de prédation chez des individus provenant de populations où le risque de prédation était élevé, la réponse augmentant avec l’intensité du stimulus. En revanche, les individus provenant de populations à faible risque de prédation semblent montrer une réponse relativement forte indépendamment de l’intensité du stimulus, ce qui suggère une hypersensibilité. Ces études corrélationnelles, portant sur l'analyse de la variabilité inter-populationnelle selon les pressions de prédation locales, nous ont amenés à supposer que ces différentes stratégies seraient intimement liées à l’expérience d’un stress chronique de la prédation. Nous suggérons alors l’existence d’un état de long-terme de type anxiété qui pourrait être la résultante de la répétition d’épisodes de court-terme de peur. Nous avons effectué un premier pas en montrant expérimentalement l’existence de comportements de peur et de type anxiété chez G. fossarum. L’ensemble de ces travaux a démontré la place centrale des interactions proie-prédateur dans l’étude de la manipulation parasitaire. Plus précisément, nous avons mis en évidence une variabilité et une modulation complexe des comportements antiprédateur des hôtes en lien avec le contexte local de prédation, et qui pourraient trouver racine dans un état émotionnel lié au stress chronique de la prédation. Ces travaux ouvrent alors quelques pistes à investiguer telles que les mécanismes sous-jacents de cet état et l’éventuel rôle des parasites dans la modulation de cet état de type anxiété qui viendrait modifier l’expression des comportements antiprédateur.
In human conscious experience, many features are present in combination: objects are presented through the senses, information from different sensory modalities is integrated, events are marked with value, and we have a sense of our own location and state. Which of these might come before others in plausible evolutionary trajectories, or do they form a tight package of correlated features that cannot readily be dissociated? I take a comparative approach to these questions, focusing on a distinction between sensory and evaluative aspects of experience and looking at the distribution of subjectivity-relevant features in a range of invertebrate animals.
Crustaceans are aquacultured both for food and as ornamental organisms. Pain and distress are not entirely understood in crustaceans, but the industry is moving towards requiring protection for the welfare of these animals during handling. In the present study, we evaluated the efficacy of clove oil as an anaesthetic for redclaw crayfish (Cherax quadricarinatus) as a model for freshwater crustaceans. We also studied how factors such as body weight and sex of redclaw could affect this efficacy. The whole experiment was replicated in two consecutive years. Redclaw juveniles were sorted into three size classes: small (<5 g), medium (5–12 g) and large (12–37 g). At least 10 males and 10 females from each size class were placed individually in water containing clove oil concentrations of 375 and 500 μl/L. Both concentrations induced rapid induction and recovery times, with 500 μl/L being the more effective concentration of the two. Induction and recovery times increased with the increase in crayfish size. No significant differences were found in induction and recovery times between male and female crayfish. Results suggest that clove oil is an effective anaesthetic for redclaw.
Animals kept as pets or for farming, including all mammals, birds and fish, have pain systems and their welfare can be poor because of pain or fear. The extent of pain can be measured using physiological and behavioural measures such as thermography or grimace scales in sheep, horses and mice. It is important to evaluate the magnitude of poor welfare, a function of severity and duration.
In general, our laws prohibit treatment of animals that causes pain or other poor welfare. However, there are exceptions in laws for reasons of tradition, financial cost, gastronomic preference, convenience in management or breeding, or avoidance of other problems. Some activities that harm animals are considered to be “sport”. For example the bull pierced by numerous lances in the corrida, the deer chased by dogs and by humans on horseback, or the dog or cock forced to fight. These “sports” have entirely negative effects for the animal. Another example is the animal killed during shechita or halal slaughter without prior stunning. The justifications for this are: tradition, edict from an interpretation of a holy book, and the mistaken belief that blood in a carcass is in some way unclean.
Evidence from welfare assessment studies shows that: cutting the throat without prior stunning causes up to two minutes of extreme pain. Castration, disbudding, or beak-trimming, without anaesthetic or analgesic causes pain for many hours, and often leads to more prolonged pain because of neuroma formation. Tail removal prevents normal defence against flies in cattle and social signalling in pigs and dogs. Tail-biting by pigs and injurious behaviour by hens can be prevented by giving the animals manipulable materials and more space. This costs more but the painful procedures can be avoided. Foie-gras production necessitates confined rearing conditions, aversive force-feeding and failure of the detoxifying function of the liver so that death would result soon after the normal killing time. Caponising is a major operation that is painful and the wounds take some days to cease to cause pain. In all these cases, the main beneficiary is human and the cost is borne by the animal.
All animals face hazards that cause tissue damage, and most have nociceptive reflex responses that protect them from such damage. However, some taxa have also evolved the capacity for pain experience, presumably to enhance long-term protection through behaviour modification based on memory of the unpleasant nature of pain. In this review, I consider various criteria that might help to distinguish nociception from pain. Because nociceptors are so taxonomically widespread, simply demonstrating their presence is not sufficient. Further, investigation of the central nervous system provides limited clues about the potential to experience pain. Opioids and other analgesics might indicate a central modulation of responses, but often, peripheral effects could explain the analgesia. Thus, reduction of responses by analgesics and opioids does not allow clear discrimination between nociception and pain. Physiological changes in response to noxious stimuli or the threat of a noxious stimulus might prove useful, but, to date, application to invertebrates is limited. Behaviour of the organism provides the greatest insights. Rapid avoidance learning and prolonged memory indicate central processing rather than mere reflexes and are consistent with the experience of pain. Complex, prolonged grooming or rubbing may demonstrate an awareness of the specific site of stimulus application. Trade-offs with other motivational systems indicate central processing, and an ability to use complex information suggests sufficient cognitive ability for the animal to have a fitness benefit from a pain experience. Recent evidence of fitness enhancing, anxiety-like states is also consistent with the idea of pain. Thus, available data go beyond the idea of just nociception, but the impossibility of total proof of pain means they are not definitive. Nevertheless, more humane care for invertebrates is suggested.
Pain is an aversive sensation and feeling associated with actual or potential tissue damage. A pain system involving receptors, neural pathways and analytical centres in the brain exists in many kinds of animals. Feelings of pain in many species are indicated by physiological responses, direct behavioural responses and ability to learn from such experiences so that they are minimised or avoided in future. Species differ in their responses to painful stimuli because different responses are adaptive in different species but the feeling of pain is probably much less variable. In early evolution, pain must have involved cell sensitivity and localised responses but efficacy would have improved with efficient communication within the individual and sophisticated brain analysis. Pain systems have probably changed rather little during vertebrate evolution. Pain may be a greater problem for animals with less cognitive ability. The distinction between pain and nociception does not seem to be useful.
This review examines the neurobehavioral nature of fishes and addresses the question of whether fishes are capable of experiencing pain and suffering. The detrimental effects of anthropomorphic thinking and the importance of an evolutionary perspective for understanding the neurobehavioral differences between fishes and humans are discussed. The differences in central nervous system structure that underlie basic neurobehavioral differences between fishes and humans are described. The literature on the neural basis of consciousness and of pain is reviewed, showing that: (1) behavioral responses to noxious stimuli are separate from the psychological experience of pain, (2) awareness of pain in humans depends on functions of specific regions of cerebral cortex, and (3) fishes lack these essential brain regions or any functional equivalent, making it untenable that they can experience pain. Because the experience of fear, similar to pain, depends on cerebral cortical structures that are absent from fish brains, it is concluded that awareness of fear is impossible for fishes. Although it is implausible that fishes can experience pain or emotions, they display robust, nonconscious, neuroendocrine, and physiological stress responses to noxious stimuli. Thus, avoidance of potentially injurious stress responses is an important issue in considerations about the welfare of fishes.
In contrast to other major forms of livestock agriculture, there is a paucity of scientific information on the welfare of fish raised under intensive aquacultural conditions. This reflects an adherence to the belief that these animals have not evolved the salient biological characteristics that are hypothesised to permit sentience. In this review, we evaluate the scientific evidence for the existence of sentience in fish, and in particular, their ability to experience pain, fear and psychological stress. Teleost fish are considered to have marked differences in some aspects of brain structure and organization as compared to tetrapods, yet they simultaneously demonstrate functional similarities and a level of cognitive development suggestive of sentience. Anatomical, pharmacological and behavioural data suggest that affective states of pain, fear and stress are likely to be experienced by fish in similar ways as in tetrapods. This implies that fish have the capacity to suffer, and that welfare consideration for farmed fish should take these states into account. We suggest that the concept of animal welfare can be applied legitimately to fish. It is therefore appropriate to recognize and study the welfare of farmed fish.
Nociception is the physiological detection of noxious stimuli. Because of its obvious importance, nociception is expected to be widespread across animal taxa and to trigger robust behaviours reliably. Nociception in invertebrates, such as crustaceans, is poorly studied.
THREE DECAPOD CRUSTACEAN SPECIES WERE TESTED FOR NOCICEPTIVE BEHAVIOUR: Louisiana red swamp crayfish (Procambarus clarkii), white shrimp (Litopenaeus setiferus), and grass shrimp (Palaemonetes sp.). Applying sodium hydroxide, hydrochloric acid, or benzocaine to the antennae caused no change in behaviour in the three species compared to controls. Animals did not groom the stimulated antenna, and there was no difference in movement of treated individuals and controls. Extracellular recordings of antennal nerves in P. clarkii revealed continual spontaneous activity, but no neurons that were reliably excited by the application of concentrated sodium hydroxide or hydrochloric acid.
Previously reported responses to extreme pH are either not consistently evoked across species or were mischaracterized as nociception. There was no behavioural or physiological evidence that the antennae contained specialized nociceptors that responded to pH.
Nociception is the detection of a noxious tissue-damaging stimulus and is sometimes accompanied by a reflex response such as withdrawal. Pain perception, as distinct from nociception, has been demonstrated in birds and mammals but has not been systematically studied in lower vertebrates. We assessed whether a fish possessed cutaneous nociceptors capable of detecting noxious stimuli and whether its behaviour was sufficiently adversely affected by the administration of a noxious stimulus. Electrophysiological recordings from trigeminal nerves identified polymodal nociceptors on the head of the trout with physiological properties similar to those described in higher vertebrates. These receptors responded to mechanical pressure, temperatures in the noxious range (more than 40 degrees C) and 1% acetic acid, a noxious substance. In higher vertebrates nociceptive nerves are either A-delta or C fibres with C fibres being the predominating fibre type. However, in the rainbow trout A-delta fibres were most common, and this offers insights into the evolution of nociceptive systems. Administration of noxious substances to the lips of the trout affected both the physiology and the behaviour of the animal and resulted in a significant increase in opercular beat rate and the time taken to resume feeding, as well as anomalous behaviours. This study provides significant evidence of nociception in teleost fishes and furthermore demonstrates that behaviour and physiology are affected over a prolonged period of time, suggesting discomfort.
Signaled avoidance learning in crayfish (Procambarus clarkii) was investigated when the crayfish were not confined, by indexing two types of locomotive movement to the escape compartment. Mild shocks, which induced tail flipping in the crayfish, and light illumination were used as unconditioned and conditioned stimuli, respectively. In Experiment 1, two groups of crayfish were trained in a one-way shuttle box. The crayfish in Group Forward were placed in the start compartment facing the escape compartment and they were able to escape/avoid shocks by walking forward, while the crayfish in Group Backward were placed in the compartment facing the opposite direction and they were able to escape by tail flipping. Avoidance learning was achieved only by walking, and not by tail flipping despite the fact that consistent tail flipping allowed the crayfish to avoid shocks. In Experiment 2, the experimental conditions were switched by using the ABA design. In this experiment, we confirmed that avoidance behavior was restricted to walking. These results are readily explained by the behavior systems approach.
It is of scientific and practical interest to consider the levels of cognitive ability in animals, which animals are sentient, which animals have feelings such as pain and which animals should be protected. A sentient being is one that has some ability to evaluate the actions of others in relation to itself and third parties, to remember some of its own actions and their consequences, to assess risk, to have some feelings and to have some degree of awareness. These abilities can be taken into account when evaluating welfare. There is evidence from some species of fish, cephalopods and decapod crustaceans of substantial perceptual ability, pain and adrenal systems, emotional responses, long- and short-term memory, complex cognition, individual differences, deception, tool use, and social learning. The case for protecting these animals would appear to be substantial. A range of causes of poor welfare in farmed aquatic animals is summarised.
In Pagurus bernhardus, the relative sizes of the crabs and shell quality of the larger crab influenced the probability of occurrence of a shell fight. These two factors along with the quality of the smaller crab's shell influenced the probability of an escalated fight occurring. During a shell fight, the attacker was able to assimilate information concerning the defender's shell and to compare it with the shell in possession. On the basis of this comparison the attacker decided whether or not to evict the defender and effect a shell change. The defending crab did not have access to information about the attacker's shell and therefore could only estimate the quality of its own shell. This asymmetry of information experienced by the crabs ensured that the attacker decided the outcome of a shell fight.-from Authors
Factors which influence decisions by hermit crabs concerning whether to approach, investigate and enter another shell have been investigated by systematically varying the size of the shell in possession and the size of the shell being offered. The probability that a crab will approach or enter the shell depends on both variables. Investigation after contact, however, depends only on the size of the shell in possession. Durations of each stage of the sequence are negatively correlated with the numbers of crabs in each experimental group performing the next stage. For the final sequence of aperture investigatory activities, the fewer crabs entering the offered shell, the greater the number of investigatory acts performed by those crabs. In addition to variation in number of acts and duration of investigation, specific use of appendages varies according to the experimental situation. Thus naked crabs use the minor cheliped to investigate shells in preference to the major cheliped, which is normally used by housed crabs, with the major cheliped being reserved for defence by naked crabs. These data are discussed in terms of information collection and decisions made on the basis of that information.
One criterion of pain experience is that the emotional response to pain may be traded-off against other motivational requirements. This was tested in hermit crabs, housed in either preferred or unpreferred species of shells, by subjecting their abdomens to electric shocks of gradually increasing intensity. The first observable response was not affected by shell species but those in preferred shells evacuated at a higher shock level than those in poor quality shells. Thus, they seem to trade-off the requirement to retain a high quality shell with that of avoidance of the noxious stimulus. Some crabs returned to their shells and those that got back into the preferred species did so with less probing of the aperture before getting in and subsequently thrust their abdomen in and out less often in further investigation, thus confirming their shell species preference. Not all crabs returned to the vicinity of the shell and some attempted to climb the wall of the experimental chamber. Others engaged in shell rapping as if in a fight and grooming of the abdomen was noted. These findings are consistent with the idea of a pain experience rather than a nociceptive reflex.
Feeding ability and motivation were assessed in the edible crab, Cancer pagurus, to investigate how the fishery practice of de-clawing may affect live crabs returned to the sea. Crabs were either induced to autotomise one claw, or were only handled, before they were offered food. Initially, autotomised and handled crabs were offered mussels, Mytilis edulis, a large part of their natural diet. After 3 days, both autotomised and handled crabs were then offered fish, a more readily handled food source. Autotomy induced crabs consumed significantly fewer mussels and less mussel mass, but ate significantly more mass of fish. This indicates that the effect of autotomy was a reduction of ability to feed on mussels rather than a general reduction of feeding motivation. The discontinuation of claw removal needs to be considered, both for the sustainability of the fishery and animal welfare concerns.
Previous work showed that goldfish learn to avoid a region of an aquarium where they receive a discrete shock to the flank. This avoidance is reduced if another fish is present next to the shock zone, suggesting fish trade-off avoidance against a tendency to associate [Dunlop, R., Millsopp, S., Laming, P., 2006. Avoidance learning in goldfish (Carassius auratus) and trout (Oncorhynchus mykiss) and implications for pain perception. App. Anim. Behav. Sci. 97 (2–4), 255–271]. Only shock intensity was adjusted in those experiments, here we report results where a requirement for food was also altered.Fish were trained to feed at a region of the aquarium where subsequently they would receive a discrete shock to the flank. One experimental group had different shock intensities applied, whereas in the other group shock intensity was consistent but food deprivation was varied.We show the number of feeding attempts and time spent in the feeding/shock zone decreased with increased shock intensity and with increased food deprivation the number and the duration of feeding attempts increased as did escape responses as this zone was entered. These data suggest that goldfish balance their need for food against avoidance of an acute noxious stimulus.
1.1. Studies were conducted on shock-avoidance leg position learning in the mud crab. Eurypanopeus depressits (Smith).2.2. Avoidance learning is associated with a significant increase in the levels of RNA and protein synthesis in the brain as well as a decrease in cholinesterase activity.3.3. Cycloheximide-induced protein synthesis inhibition results in a significant impairment of the learning process.4.4. The protocerebrum was identified as the brain region most associated with avoidance learning in this species. Increased RNA activity was found to occur in the protocerebral bridge and central body of the protocerebral region.5.5. Localization of brain function with respect to learning in decapod crustaceans is discussed.
We consider evidence that crustaceans might experience pain and stress in ways that are analogous to those of vertebrates. Various criteria are applied that might indicate a potential for pain experience: (1) a suitable central nervous system and receptors, (2) avoidance learning, (3) protective motor reactions that might include reduced use of the affected area, limping, rubbing, holding or autotomy, (4) physiological changes, (5) trade-offs between stimulus avoidance and other motivational requirements, (6) opioid receptors and evidence of reduced pain experience if treated with local anaesthetics or analgesics, and (7) high cognitive ability and sentience. For stress, we examine hormonal responses that have similar function to glucocorticoids in vertebrates. We conclude that there is considerable similarity of function, although different systems are used, and thus there might be a similar experience in terms of suffering. The treatment of these animals in the food industry and elsewhere might thus pose welfare problems.
The occurrence of empty gastropod shells and those occupied by the hermit crab, Pagurus bernhardus, was examined on the shore. This survey suggested that small crabs prefer L. littoralis shells to those of Gibbula species and this was confirmed by preference tests in the laboratory. Crabs removed from these small shells show an initial preference for Nucella shells to those of L. littorea. However, medium sized crabs collected in either Nucella or L. littorea prefer the species in which they were collected. This preference is still apparent when the size of the test shells is varied. These data provide the first clear evidence for a modification of shell preferences after experience of particular shell species.
Pain is mediated by functionally distinctive components. It may involve acute high threshold afferent stimuli (thermal, mechanical or chemically damaged tissue), protracted afferent input (long-lasting hyperalgesia) or low-threshold input (allodynia as related to pain from light touch). Behavioral patterns will be associated with the effects of noxious stimulus on excitatory transmitters. Humane studies using mechanical, thermal (cold pressor test), audio-evoked potentials, or other noxious stimuli during anesthesia and analgesia provide clues to perception of pain in animals and help us determine guidelines for the clinical relief of animal pain. There is a better understanding of cutaneous somatosensory responses than for deep sensation (e.g., subcutaneous tissue, muscle, bone, viscera). The prevention or treatment of pain can best be accomplished when there is a diagnosis of the neuroanatomical distribution of the pain based on evidence of sensory dysfunction involving a peripheral nerve, plexus, nerve root or central pathway using different modalities for quantitative sensory testing. Anatomical studies have demonstrated that unmyelinated primary afferent fibers contain a variety of neuroactive substances which may be released by high-intensity peripheral stimulation. Fast depolarization of the dorsal horn nociresponsive neurons is mediated by tissue damage. These neuroreceptors may be activated by glutamate, substance P, and neurokinin A. The major ascending pathway relaying nociceptive information relating to pain is the spinothalamic tract. Most of the neurons in this tract are nociceptive or thermoreceptive. The thalamus is the final relay nucleus for all the sensory systems, except olfactory tissue. Injury or disease processes in deeper tissue or visceral areas with extensive innervation may result in pain thresholds not adequately controlled by current available analgesics or at their recommended dosage levels. These issues are complex and diagnosis is even more difficult due to species and breed differences in outward expression to painful insult. Medications can now be targeted for specific receptors.
It is a popular notion that, compared to vertebrates, invertebrates have a reduced capacity to experience suffering. This is usually based on arguments that invertebrates show only simple forms of learning, have little memory capacity, do not show behavioural responses to stimuli that would cause 'higher' vertebrates to exhibit responses indicative of pain, and have differences in their physiology that would preclude the capacity for suffering. But, how convincing is this 'evidence' of a reduced capacity to suffer? Suffering is a negative mental state – a private experience – and, as such, it cannot be measured directly. When assessing the capacity of an animal to experience suffering, we often compare the similarity of its responses with those of 'higher' animals, conceptualized in the principle of argument-by-analogy. By closely examining the responses of invertebrates, it can be seen that they often behave in a strikingly analogous manner to vertebrates. In this paper, I discuss published studies that show that invertebrates such as cockroaches, flies and slugs have short- and long-term memory; have age effects on memory; have complex spatial, associative and social learning; perform appropriately in preference tests and consumer demand studies; exhibit behavioural and physiological responses indicative of pain; and, apparently, experience learned helplessness. The similarity of these responses to those of vertebrates may indicate a level of consciousness or suffering that is not normally attributed to invertebrates. This indicates that we should either be more cautious when using argument-by-analogy, or remain open-minded to the possibility that invertebrates are capable of suffering in a similar way to vertebrates.
Myograms were recorded from crabs being trained to raise their legs to avoid shocks. Shock avoidance was associated with an increase in the firing frequency of a slow tonic flexor motoneuron, whose firing frequency increased with increased carpopodite flexion. The firing frequency of this motoneuron could be directly altered by means of a computer‐controlled training procedure. When shocks were given whenever the frequency was below a predetermined threshold, significant increases in frequency were obtained compared with control animals that received the same regime of shocks as experimental crabs.
Decerebrate crabs were trained to raise their legs to avoid electric shocks. Compared with yoked controls, experimental crabs received significantly fewer shocks after 6–7 minutes training and also during the first minute of a subsequent testing period when both experimental and control crabs were in a training situation. There was considerable variation in the performance of different crabs. Some learned quickly, some slowly, while others did not learn at all. In some, the raised leg position was maintained without further reinforcement. In others, periods when the animal was receiving few shocks were interrupted by periods when the leg was lowered and several shocks were received. A variety of leg movements were utilised by crabs to avoid shocks, the most common being flexion at the mero‐carpopodite joint.
Animals are routinely subjected to painful procedures, such as tail docking for puppies, castration for piglets, dehorning for dairy calves, and surgery for laboratory rats. Disease and injury, such as tumours in mice and sole ulcers on the feet of dairy cows, may also cause pain. In this paper we describe some of the ways in which the pain that animals experience can be recognized and quantified. We also describe ways in which pain can be avoided or reduced, by reconsidering how procedures are performed and whether they are actually required. Ultimately, reducing the pain that animals experience will require scientific innovation paired with changed cultural values, and willingness to address regulatory, technological and economic constraints. # 2006 Published by Elsevier B.V.
In this paper I explore the value of invertebrates to human society. I initially examine various ecological, utilitarian, scientific, and cultural benefits provided by invertebrate organisms. I then explore the extent of appreciation and understanding of these values among the American public. This assessment was based on a study of residents of the state of Connecticut, including randomly selected members of the general public, farmers, conservation organization members, and scientists. The general public and farmers were found to view most invertebrates with aversion, anxiety, fear, avoidance, and ignorance. Far more positive and knowledgeable attitudes toward invertebrates and their conservation were observed among scientists and, to a lesser extent, among conservation organization members. I finally examine the motivational basis for hostile attitudes toward invertebrates, particularly arthropods among the general public. Important factors include the possibility of an innate learning disposition, the association of many invertebrates with disease and agricultural damage, differences in ecological scale between humans and invertebrates, the multiplicity of invertebrates, the apparent lack of a sense of identity and consciousness among invertebrates, the presumption of mindlessness among invertebrates, and the radical autonomy of invertebrates from human control.
We examined physiological stress responses in the edible crab, Cancer pagurus, subjected to the commercial fishery practice of manual de-clawing. We measured haemolymph glucose and lactate, plus muscular
glycogen and glycogen mobilisation, in three experiments where the crabs had one claw removed. In the first, crabs showed
physiological stress responses when ‘de-clawed’ as compared to ‘handled only’ over the short term of 1–10min. In the second,
de-clawing and the presence of a conspecific both increased the physiological stress responses over the longer term of 24h.
In the third, de-clawing was shown to be more stressful than ‘induced autotomy’ of claws. Further, the former practice caused
larger wounds to the body and significantly higher mortality than the latter. Since the fishery practice is to remove both
claws, the stress response observed and mortality data reported are conservative.
1. Administration of biogenic amines into intact Carcinus maenas induces dose- and timedependent elevation of hemolymph glucose level.2. Removal of the neurosecretory centre containing the crustacean hyperglycemic hormone (CHH) by ablation of the eyestalks did not induce hypoglycemia.3. Injection of dopamine (DA) into eyestalkless crabs showed no hyperglycemic effect, while serotonin (5-HT), epinephrine (E), norepinephrine (NE), and octopamine (OA) elevated glucose levels.4. The dopaminergic effect was significantly reduced by administration of trifluoperazine (TFP).5. 5-HT and OA were found to be strong elevators of glucose levels, while the other biogenic amines had moderate effects only.6. The results indicate, that DA exerts its hyperglycemic effect by stimulating the release of CHH from the eyestalk neurosecretory centre. Elevation of hemolymph glucose level by 5-HT, OA, E, and NE, occurs independently of CHH.
Judgements about pain and suffering in animals are required by the law of many countries and by many professional guidelines. Nevertheless, such assessments raise many problems, even in humans. Furthermore, an appeal to continuities between humans and other animals is clouded when, as is still the case, both the evolution and the function of a subjective sense of pain are obscure. Despite these difficulties, the criteria that lead to the judgement that a human is in pain can be generalized with substantial measure of agreement to other animals. This generalization is done on the basis of uncovering comparable mechanisms and comparable behaviour; then the whole cluster of features found in the animal is used to make the judgement. The less similar the animal to a human and the less complex it is, the more difficult is the assessment. The fuzziness of the boundary between those animals that are judged to feel pain and those that are not does not invalidate the process of assessment. However, the extent to which an animal is given the benefit of the doubt clearly depends on the empathy a person feels for it as well as the type of ethical concerns that motivate the person.
Nociception is the ability to perceive a noxious stimulus and react in a reflexive manner and occurs across a wide range of taxa. However, the ability to experience the associated aversive sensation and feeling, known as pain, is not widely accepted to occur in nonvertebrates. We examined the responses of a decapod crustacean, the prawn, Palaemon elegans, to different noxious stimuli applied to one antenna to assess reflex responses (nociception) and longer-term, specifically directed behavioural responses that might indicate pain. We also examined the effects of benzocaine, a local anaesthetic, on these responses. 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.
Pain may be inferred when the responses to a noxious stimulus are not reflexive but are traded off against other motivational requirements, the experience is remembered and the situation is avoided in the future. To investigate whether decapods feel pain we gave hermit crabs, Pagurus bernhardus, small electric shocks within their shells. Only crabs given shocks evacuated their shells indicating the aversive nature of the stimulus, but fewer crabs evacuated from a preferred species of shell indicating a motivational trade-off. Some crabs that evacuated attacked the shell in the manner seen in a shell fight. Most crabs, however, did not evacuate at the stimulus level we used, but when these were subsequently offered a new shell, shocked crabs were more likely to approach and enter the new shell. Furthermore, they approached that shell more quickly, investigated it for a shorter time and used fewer cheliped probes within the aperture prior to moving in. Thus the experience of the shock altered future behaviour in a manner consistent with a marked shift in motivation to get a new shell to replace the one occupied. The results are consistent with the idea of pain in these animals.
The value of contested resources (shells) in hermit crab fights depends on the sizes of the crabs relative to the sizes of the resources. Thus when relative contestant size is the main experimental variable, motivational factors associated with shell size will also be an experimental problem. Two experiments are described that together overcome this problem. Relative crab size influences all stages of shell fights including pre-fight display, escalation, eviction and examination of the opponent's shell by the victor both before and after eviction of the loser. Shell fights occur more often between disparately-sized animals than between those similar in size. This apparent contradiction of recent theory (Maynard-Smith & Parker 1976) is probably due to the high cost of being without a shell and the small chance that an escalated fight will result. Relative crab size influences the time taken in resource assessments and thus the effectiveness of these assessments is also probably influenced. Causal factors influencing each of the major decisions in shell fights are described and although these fights are more complex than most they are in general agreement with theory on animal contests.
Nonreflexive responses to a noxious event and prolonged memory are key criteria of a pain experience. In a previous study, hermit crabs, Pagurus bernhardus, that received a small electric shock within their shell often temporarily evacuated the shell and some groomed their abdomen and/or moved away from their vital resource. Most, however, returned to the shell. When offered a new shell 20 s later, shocked crabs were more likely than nonshocked crabs to approach and move into a new shell and did so more quickly (Elwood & Appel 2009, Animal Behaviour, 77, 1243–1246). Here we examined how increasing the time between the shock and the offering of a new shell influences the response. There was evidence of a memory of the aversive shock that lasted at least 1 day. Crabs tested after 30 min and 1 day were more likely to approach the shell and new shells were more likely to be taken 30 min after the shock. Shocked crabs approached the new shell more quickly and used fewer probes of the chelipeds prior to moving in and these results were stable over time and significant for specific times up to 1 day. Females were more likely than males to evacuate shells and did so after fewer shocks. These results extend previous work and demonstrate an extended memory of having been shocked. The findings are consistent with respect to criteria for pain that are accepted for vertebrates.
All animals face hazards that cause tissue damage and most have nociceptive reflex responses that protect them from such damage. However, some taxa have also evolved the capacity for pain experience, presumably to enhance long-term protection through behavior modification based on memory of the unpleasant nature of pain. In this article I review various criteria that might distinguish nociception from pain. Because nociceptors are so taxonomically widespread, simply demonstrating their presence is not sufficient. Furthermore, investigation of the central nervous system provides limited clues about the potential to experience pain. Opioids and other analgesics might indicate a central modulation of responses but often peripheral effects could explain the analgesia; thus reduction of responses by analgesics and opioids does not allow clear discrimination between nociception and pain. Physiological changes in response to noxious stimuli or the threat of a noxious stimulus might prove useful but, to date, application to invertebrates is limited. Behavior of the organism provides the greatest insights. Rapid avoidance learning and prolonged memory indicate central processing rather than simple reflex and are consistent with the experience of pain. Complex, prolonged grooming or rubbing may demonstrate an awareness of the specific site of stimulus application. Tradeoffs with other motivational systems indicate central processing, and an ability to use complex information suggests sufficient cognitive ability for the animal to have a fitness benefit from a pain experience. Available data are consistent with the idea of pain in some invertebrates and go beyond the idea of just nociception but are not definitive. In the absence of conclusive data, more humane care for invertebrates is suggested.
This paper investigates spatially cued behavioural responses of two species of fish to an acute noxious stimulus and demonstrates response elasticity. Typical avoidance responses to a nociceptive stimulus were used to test (1) if fish learn to avoid spatial areas associated with a potentially noxious stimulus, (2) learning and memory improves with increased stimulus intensity and (3) a supposedly innate reflex behavioural responses change depending on the circumstances. Electric shocks with two different intensities, low (2.5 V and 3 V for trout and goldfish, respectively) and high (25 V and 30 V for trout and goldfish, respectively), were administered directly to the skin to stimulate cutaneous nociceptors. Goldfish (n = 8) demonstrated spatially cued shock avoidance and an increase in stimulus voltage, significantly improved shock-avoidance learning and memory. However, trout (n = 8) demonstrated shock-avoidance learning but no significant stimulus discrimination and little information retention. The presence of a conspecific significantly changed this behavioural response to a noxious stimulus. Trout were willing to remain in the vicinity of the conspecific while being subjected to low intensity shock stimuli previously shown to elicit avoidance. Goldfish tended to leave this area yet remain in the mid-tank area, adjacent to the stimulating zone, rather than at the end of the tank. These results suggest that shock avoidance in fish is not purely a reflex action. Fish were prepared to change the supposedly innate avoidance reaction according to a change in circumstances, an important concept in the ongoing debate on pain perception in fish. (c) 2005 Elsevier B.V. All rights reserved.
Recent evidence has shown that fish display aversive behavioral and physiological reactions and a suspension of normal behavior in response to noxious stimuli that cause pain in other animals and humans. In addition to these behavioral responses, scientists have identified a peripheral nociceptive system and recorded specific changes in the brain activity of fish during noxious stimulation. As a result of these observations teleost fish are now considered capable of nociception and, in some opinions, pain perception. From both an experimental and an ethical perspective, it is important that scientists be able to assess possible pain and minimize discomfort that may result from invasive or other noxious procedures. If scientists accept that the definition of pain in animals cannot include direct measurement of subjective experience (the standard for humans), then fish fulfill the criteria for animal pain. In this review, recent evidence for pain is discussed in terms of the physiological properties of nociceptors, central responses to noxious stimulation, and changes in behavior and physiology that are indicative of nociception and are responsive to analgesia. To enable the assessment of potential pain, there are descriptions of newly identified robust indicators and species-specific responses that are easily measurable. The article concludes with a discussion of humane endpoints and of the need for alleviation of pain through the use of analgesia and anesthesia.
Experiments were carried out on the ability of single legs of the whole ghost crab Ocypode ceratophthalma to learn to avoid the receipt of electric shocks coupled with leg position (the Horridge paradigm). Ocypode is a common, hardy, very active, air-breathing subtropical species. Aversive shocks were delivered through a silver wire attached to the dactylopodite whenever the leg was lowered into a dish of sea water. Tests were made comparing position (P) animals with yoked (random, R) controls, on intact crabs and also ones from which the cerebral ganglion had been removed. Preparations that showed leg-position learning were then subjected to further training by bringing them sufficiently close to the water to receive shocks again. All of the animals tested showed some initial improvement in shock avoidance. This was always achieved by the use of one or more natural flexion movements, the commonest being at the meropodite/carpodite, followed by the coxopodite/basipodite, and the propodite/dactylopodite. In successive training, progressively greater flexion was achieved by the use of one or more additional joints. Debrained animals learned better than intact ones. Yoked controls performed badly and often did not learn at all when tested as position animals immediately after the animal they were linked with had learned to avoid shocks. Learning occurred about six times as fast as in comparable insect preparations, under 2 min compared with an average of 8 min. But retention, either with or without reinforcement, was much shorter in the crab preparations than in their insect counterparts; 3 to 4 hr compared with 2 days or more. It is concluded that crab preparations may be valuable for exploration of the cellular neuronal mechanisms underlying shock-avoidance leg-position learning.
A modified formalin test in mice was investigated. The pain response curve induced by 0.5% formalin was biphasic, having 2 peaks, from 0 to 5 min (first phase) and from 15 to 20 min (second phase). A low concentration of formalin was used, allowing the effects of weak analgesics to be detected. Centrally acting drugs such as narcotics inhibited both phases equally. Peripherally acting drugs such as aspirin, oxyphenbutazone, hydrocortisone and dexamethasone only inhibited the second phase. Aminopyrine and mefenamic acid which acted on both central and peripheral sites inhibited both phases, but the second phase was inhibited by lower doses. Thus, this method enables one to easily distinguish the site of action of analgesics. Furthermore, pain response in the first phase was inhibited by capsaicin-treated desensitization and Des-Arg9-(Leu8)-bradykinin (bradykinin inhibitor). The second phase was inhibited by compound 48/80 pretreatment, indomethacin and bradykinin inhibitor. Therefore, it is suggested that substance P and bradykinin participate in the manifestation of the first phase response, and histamine, serotonin, prostaglandin and bradykinin are involved in the second phase. These results indicate that the first and second phase responses induced by formalin have distinct characteristic properties, and it is a very useful method for examining pain, nociception and its modulation by pharmacological or other means.
Male crabs Chasmagnathus granulatus were trained by means of a method similar to the standard inhibitory avoidance technique widely used in vertebrates. Each crab was placed in the dark compartment (DC) of a double-chamber device, allowed to move towards the light compartment (LC) and latency to enter measured. Experimental crabs received a shock in LC, but controls were not punished. After 1 min, both experimental and control crabs were free to return to DC. On completion of 1, 2, 3 or 24 hr intertrial interval in DC a retention test was administered and latency to enter LC was measured. A single trial was proven enough to establish a LC-shock association that was detected up to 3 hr later, but no retention was proved after 24 hr. Memory was disrupted when crabs were removed from the apparatus during the 3 hr intertrial interval. Similarities and differences between the passive avoidance method used with crabs and that used with vertebrates are discussed.
Due to the combination of multidisciplinary studies, the last fifteen years have seen a major step forward in our knowledge of nociception. At the peripheral level the role of A delta and C polymodal cutaneous nociceptors is relatively well demonstrated in animal as well as in man. The activation of these nociceptors probably results from both direct effects of the stimulus and indirect effects, mediated by the release of various chemicals. The specific roles of articular, muscular and visceral fine afferent fibers in nociception, is less well understood. Cutaneous A delta and/or C fibers terminate mainly in the superficial zones (laminae I and II outer) of the dorsal horn. The nature of the transmitter (s) released by nociceptive afferents is still unknown. Substance P has long been a candidate but the multiplicity of peptides revealed by immunohistochemical techniques and their coexistence on occasions in the same dorsal root ganglion cells question a unequivocal role of substance P. At the level of the dorsal horn of the spinal cord, nociceptive specific and nociceptive non-specific units have been described in laminae I, II, IV to VI. It is generally held that nociceptive specific neurons are mainly found in the superficial laminae which also contains nociceptive non specific cells. Convergence of cutaneous, muscular and visceral inputs on these neurons is indicative of a role of both cell types in referred pain where consideration must also be given to the possibility of dichotomizing afferent fibers serving cutaneous and visceral territories. The involvement of contralateral ascending pathways (spinothalamic and spinoreticular tracts) in the transmission of nociceptive messages toward supraspinal structures is well established while the role of ipsilateral ascending systems (spino-cervical and dorsal columns post-synaptic fibers) is still questioned. Both segmental and descending modulating controls are exerted at the spinal level. At segmental levels, the inhibitory action of large diameter cutaneous fibers is now well established. The action of fine fibers seems also to be inhibitory. Descending influences are exerted from the periaqueductal gray matter and the ventromedial medulla (mainly the nucleus raphe magnus). They are sustained by serotoninergic and noradrenergic mechanisms and they involve to a lesser extent the endogenous opioids. The physiological function of these descending systems is still sharply discussed.
In this extensive review devoted to nociception the authors successively cover peripheral phenomena, spinal mechanisms, ascending tracts, and finally the segmental and descending control systems. They above all cover the results obtained at the spinal level.
Lame and sound broilers, selected from commercial flocks, were trained to discriminate between different coloured feeds, one of which contained carprofen. The two feeds were then offered simultaneously and the birds were allowed to select their own diet from the two feeds. In an initial study to assess the most appropriate concentration of drug, the plasma concentrations of carprofen were linearly related to the birds' dietary intake. The walking ability of lame birds was also significantly improved in a dose-dependent manner and lame birds tended to consume more analgesic than sound birds. In a second study, in which only one concentration of analgesic was used, lame birds selected significantly more drugged feed than sound birds, and that as the severity of the lameness increased, lame birds consumed a significantly higher proportion of the drugged feed.
This study aimed to assess fear responses to a novel object while experiencing a noxious event to determine whether nociception or fear will dominate attention in a fish in novel object testing paradigm. This experimentally tractable animal model was used to investigate (1) the degree of neophobia to a novel object while experiencing noxious stimulation, (2) the response of the fish after removing the fear-causing event by using a familiar object, and (3) the effects of removing the nociceptive response by morphine administration and examining the response to a novel object. Control animals displayed a classic fear response to the novel objects and spent most of their time moving away from this stimulus, as well as showing an increase in respiration rate when the novel object was presented. In contrast, noxiously stimulated animals spent most of their time in close proximity to the novel object and showed no additional increase in respiration rate to novel object presentation. There was evidence of a slight hypoalgesia in noxiously stimulated animals. The responses to familiar objects demonstrated that by familiarizing the animal with the object, fear was removed from the experiment. Both control and noxiously treated animals responded in similar ways to a novel object by spending the majority of their time in close proximity. Treatment with morphine reduced effects of noxious stimulation and appears to be an effective analgesic. After morphine administration, the acid-injected animals showed a neophobic response to a novel object and this was similar to the response of the control fish, with a similar amount of time spent moving away from the object and an increase in ventilation in response to the novel object. Morphine affected the fear response because both groups approached the novel object more quickly than the non-morphine controls. These results suggest that nociception captures the animal's attention with only a relatively small amount of attention directed at responding to the fear of the novel object.
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