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Pain and stress in crustaceans?
Abstract
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.
... It has been linked to excessive greenhouse gas production and coastal effluent pollution and is increasingly vulnerable to disease outbreaks and the warming climate [1, [6][7][8][9][10]. Furthermore, as crustaceans are becoming recognized as sentient, current fishing and farming methods are unlikely to meet emerging animal welfare standards [11][12][13]. Alternative and ...
... is increasingly vulnerable to disease outbreaks and the warming climate [1, [6][7][8][9][10]. Furthermore, as crustaceans are becoming recognized as sentient, current fishing and farming methods are unlikely to meet emerging animal welfare standards [11][12][13]. Alternative and complementary production methods, such as cell cultivation, are needed to ensure we have a more sustainable and ethical global supply of these foods. ...
... To anesthetize crayfish, temperature cooling was used in conjunction with the anesthetic/analgesic product Aqui-S, purchased from Primo Aquaculture, Narangba, Australia. This approach was based on previous studies investigating crustacean responses to analgesia [12,57]. Anesthesia was considered effective when crayfish remained motionless despite pressure being applied to their highly innervated anal region. ...
In the face of rising global demand and unsustainable production methods, cultivated crustacean meat (CCM) is proposed as an alternative means to produce delicious lobster, shrimp, and crab products. Cultivated meat requires starting stem cells that may vary in terms of potency and the propensity to proliferate or differentiate into myogenic (muscle-related) tissues. Recognizing that regenerating limbs are a non-lethal source of tissue and may harbor relevant stem cells, we selected those of the crayfish Cherax quadricarinatus as our model. To investigate stem cell activity, we conducted RNA-Seq analysis across six stages of claw regeneration (four pre-molt and two post-molt stages), along with histology and real-time quantitative PCR (qPCR). Our results showed that while genes related to energy production, muscle hypertrophy, and exoskeletal cuticle synthesis dominated the post-molt stages, growth factor receptors (FGFR, EGFR, TGFR, and BMPR) and those related to stem cell proliferation and potency (Cyclins, CDKs, Wnts, C-Myc, Klf4, Sox2, PCNA, and p53) were upregulated before the molt. Pre-molt upregulation in several genes occurred in two growth peaks; Stages 2 and 4. We therefore propose that pre-molt limb regeneration tissues, particularly those in the larger Stage 4, present a prolific and non-lethal source of stem cells for CCM development.
... Stressors trigger a neuroendocrine response (primary response) that evokes physiological and behavioural efects (secondary response) to restore homeostasis. If persistent, stressor may induce systemic changes afecting the performance of the animal [21][22][23][24][25]. ...
... Tere are many molecules and corresponding receptors linked to nociception such as transient receptor potential (TRP) channels and opioid receptors that have been reported in decapod crustaceans [24,[51][52][53][54]. TRP channels control temperature and mechanical nociception, transducing noxious stimuli into currents [54]. ...
... Wounded crustaceans show activities such as rubbing, limping or grooming that indicate awareness of the site of the wound and some attempt to reduce further damage [15,24]. Indeed, such behaviour has been interpreted as being consistent with pain [62]. ...
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.
... In decapod crustaceans it involves a specific neuromuscular reflex acting across a fixed cuticular plane of fracture [56], although there may be a degree of voluntary control [64]. In addition to specific mechanosensory stimuli, crabs show autotomy when an appendage has been subjected to various other stimuli such as heating, cooling on ice, shock, wounding, acetic acid injection or minor electric shocks to the appendages [65]. ...
... This is especially striking since attempts to electrically stun crabs using a low electrical field strength to the whole animal [30] failed to inactivate the animals, but actually caused extensive autotomy. Moreover, Elwood et al. (2009) found that weak electrical stimuli applied to the legs induced them to autotomise [65]. A plausible interpretation of these different findings is that weak electrical stimuli artificially activate the sensory and/or motor pathways involved in the autotomy reflex, resulting in the shedding of the limb, whereas electrical stunning with higher electrical field strengths inactivates these pathways rapidly and completely, before the reflex neuromuscular action underlying autotomy can be elicited, so that no limb losses occur. ...
... This is especially striking since attempts to electrically stun crabs using a low electrical field strength to the whole animal [30] failed to inactivate the animals, but actually caused extensive autotomy. Moreover, Elwood et al. (2009) found that weak electrical stimuli applied to the legs induced them to autotomise [65]. A plausible interpretation of these different findings is that weak electrical stimuli artificially activate the sensory and/or motor pathways involved in the autotomy reflex, resulting in the shedding of the limb, whereas electrical stunning with higher electrical field strengths inactivates these pathways rapidly and completely, before the reflex neuromuscular action underlying autotomy can be elicited, so that no limb losses occur. ...
Increasing attention is being paid to the welfare of decapod crustaceans. Legislation exists for their humane slaughter in several countries and this is being debated in others. Electrical stunning may have potential for humane slaughter of crustaceans in some circumstances, although scientific data on the effectiveness of electrical stunning when applied to various species are limited. Assessment criteria for effective stunning have so far been based mainly on behavioural assessments, but these do not always reflect neural insensibility. In this study direct recordings of neural activity, both centrally and peripherally, have been used to provide more direct measures of the state of sensibility. We have also examined whether electrical stunning acts as a physiological stressor, using measures of haemolymph L-lactate. Experiments were performed on a commercially important decapod species, the brown crab Cancer pagurus L. Spontaneous activity within the CNS was arrested by electrical stunning, which is an indication of loss of sensibility. There were also specific effects on the peripheral nervous system, with loss of responsiveness to sensory stimulation, rendering the animals unresponsive to external stimuli, and a failure of motor activation. All these effects were apparent immediately after a 10s stun, and persisted for as long as tested (4h) indicating that the animals were also killed by the procedure. No autotomy of limbs occurred. Haemolymph L-lactate was found to be no greater following electrical stunning than after handling and sampling alone, and both were significantly lower than values reached in a range of environmental and commercial situations. For all these reasons we find that electrical stunning may meet criteria for humane slaughter of C. pagurus.
... Generally, this effect is expressed with behaviors such as a lesser effort to avoid the sources of pain, as shown in snails (Kavaliers et al., 1983). Related to the similarity between the physiological changes associated to the experience of pain in vertebrates and invertebrates, we can also emphasize pupil dilatation, changes in blood and respiration flow rates, and stress or relative changes in the endocrine system (Elwood et al., 2009;Elwood, 2011). In the light of this evidence, some researchers have already claimed the use of analgesics and anesthetics in research with invertebrates (Lockwood, 1987(Lockwood, , 1988Crook & Walters, 2011). ...
... After one minute they are returned to the dark compartment. With only one trial, the crabs are unwilling to return to the illuminated compartment after 3 hours (Elwood et al., 2009). When they have undergone this process several times, the crabs display this behavior until up to 24 hours later. ...
... When they have undergone this process several times, the crabs display this behavior until up to 24 hours later. Similar investigations have been carried out with fruit flies (Yarali et al., 2008), cockroaches or ants (Broom, 2013), and lobsters (Elwood et al., 2009). The results of this research concerning memory and painavoidance learning provides solid reasons to conclude that, if we accept that vertebrates experience pain, the same must be concluded in the case of at least some invertebrates. ...
Invertebrate animals are usually seen as a kind of “aliens” which do not deserve any moral consideration. However, there is a growing amount of evidence indicating that many of them do have the capacity to experience pain. The same criteria that are usually applied in order to infer that vertebrates are sentient beings (behavioral response, learning capacity, memory, a certain specific neurophysiological structure…) lead to the idea that many invertebrates are sentient as well. Therefore, under the skeptical premise that we have no direct evidence of the experience of pain in vertebrates, we are forced to hold that it exists in both vertebrates and invertebrates.
... When they fire, they initiate a reflex by which the animal withdraws part or all of its body to avoid further noxious stimuli. Importantly for understanding the complexity of pain, the reflex does not necessarily involve the central nervous system or central processing and does not necessarily produce the emotional experience of pain [10]. Thus, simply noting that an animal avoids noxious stimuli does not enable pain to be inferred. ...
... For example, numerous studies on Drosophila have been key to our understanding the development and functioning of these nerve cells [11]. They have been much less studied in decapods, but they have been inferred from the behavioural responses of these animals and from examination of surface receptors [10]. Decapods respond to mechanical, thermal, and chemical stimuli [7,12], and receptors have been described that respond to those stimuli [7,13]. ...
... In vertebrates, it causes a cascade of hormonal changes that leads to the production of adrenal hormones (cortisol and corticosterone), which stimulate the conversion of glycogen to glucose used in the fight-or-flight response. In decapods, stress releases the crustacean hyperglycemic hormone (CHH), which has broadly similar effects to those adrenal hormones in vertebrates [10], or by releasing biogenic amines such as epinephrine and serotonin [38,39]. ...
Simple Summary
Decapods respond to noxious stimuli in ways that are consistent with the experience of pain; thus, we accept the need to provide a legal framework for their protection when they are used for human food. We review the main methods used to slaughter the major decapod crustaceans, highlighting problems posed by each method for animal welfare. The aim is to identify methods that are the least likely to cause suffering. These methods can then be recommended, whereas other methods that are more likely to cause suffering may be banned. We thus request changes in the legal status of this group of animals, to protect them from slaughter techniques that are not viewed as being acceptable.
Abstract
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.
... Crustacean hyperglycaemic hormone (CHH) is stated by some the functional equivalent to cortisol in finfish (Elwood et al., 2009), but it may not be the most practicable. CHH is synthesised, stored and released by the eyestalk X-organ in decapod crustaceans (Loredo-Ranjel et al., 2017). ...
... Crustaceans often endure extreme conditions during capture, storage, trade as live food and slaughter (Crump et al., 2022;Elwood et al., 2009), with a distinct lack of standardised practices and welfare across food systems and countries. The extent of harm caused by noncommunicable (physical) stressors is not fully understood. ...
Decapod crustacean welfare is not only an ethical consideration for legislative purposes. Under culture and fishery settings, poor environmental conditions and operator practices can cause stress, which compromises the immune system and increases the risk of disease. For finfish, there are established environmental and animal (group, individual) welfare indicators. This is not the case for crabs, lobsters or shrimp. While environment-based indicators like temperature, pH and oxygen levels are easily transferable, there is no consensus for a common measure of stress to monitor welfare in decapod crustaceans. To address this shortcoming, we conducted a meta-analysis of the primary literature to test for relationships between haemolymph (blood) condition, for example, levels of glucose, L-lactate, haemocytes (n = 8), and sources of physical stress, for example, handling, trawling, emersion and transport (n = 12). Despite variations in effect sizes (n = 459), generalised linear mixed models repeatedly ranked L-lactate (followed by urea and glucose) as the most significant physiological predictor of stress in the haemolymph, with trawling followed closely by emersion as the most impactful stressors. Duration post (stress) exposure, sex (male, female), water temperature and moult stage (pre-, inter-, post-moult) were not associated significantly with stress prediction using the selected biochemical and cellular parameters, however, moult status was undefined in ~48% of literature sources and should be interpreted with caution. We present evidence that quantitating L-lactate levels in the haemolymph represents a physiologic operational welfare indicator of decapod crustaceans, which complements existing condition/vigour indices.
... Crabs reared under stress conditions could result in lower survival and growth performance (Lu et al., 2019;Shi et al., 2019). As the primary stress hormone in animals (Tataranni et al., 1996), cortisol is commonly applied as a stress indicator for crustaceans (Elwood et al., 2009;Yong et al., 2020) for elevated cortisol levels are known to negatively affect the immune defense of aquatic animals (Harris and Bird, 2000). In the present study, the highest cortisol content was detected in crabs exposed to an 18 L∶6 D photoperiod; the group also had the lowest survival rate compared with other treatments, suggesting the crabs could be stressed. ...
... However, the current research on cortisol in crustaceans is relatively limited, and the concentrations detected in different tissues vary greatly. Besides, cortisol has similar physiological functions to crustacean hyperglycemic hormone (CHH) in crustaceans that regulates energy metabolism (Elwood et al., 2009). Additionally, different photoperiods and stress statuses can elicit different daily cortisol profiles, which resulting changes in acrophase and amplitude (Pavlidis et al., 1999). ...
... This may involve housing decapods in rock pools, removing decapods from the water and allowing children to feel their shells. In some cases, time kept out of water can vary, with a guideline of 'just a few minutes' [28]-this has been proven to have a detrimental impact on animal welfare [38]. ...
... Data Availability Statement: Both adapted AWAG templates and all data gathered and used are available at: [38]-hNtlAf5abqx8aS7JZda?dl=0; Software used in this study is available at: https: //zoo.awag.org.uk/ (accessed on 20 May 2022). ...
Simple Summary
The use of decapods (such as lobsters and crabs) and cephalopods (such as octopuses and cuttlefish) by humans for food, experimentation and education (e.g., in zoos and aquariums) is on the increase. Growing evidence that these species have feelings and can experience emotions has highlighted the need for a tool to monitor the welfare of these species in captivity. This study adapted a welfare monitoring tool, the Animal Welfare Assessment Grid, that has been successfully used with a variety of mammal and bird species, for use with decapods and cephalopods. This tool was then trialed at a zoological institution (Marwell Zoo, UK) and, for the first time, a public aquarium (National Marine Aquarium, UK), with the intention of showing how data collected on invertebrates in a zoological environment can be both efficiently and easily applied to implement positive welfare. This study highlights how evaluating the welfare impact of management processes using animal-based indicators can lead to improved welfare outcomes.
Abstract
Consumer demand for invertebrates is on the rise as their numbers in the wild dwindle. However, with the growing conservation efforts of modern zoos and aquariums, and evidence from over 300 studies showing that invertebrates are capable of sentience, public interest, and moral concern for welfare of invertebrates have increased. The challenge for zoos and aquariums is in developing an objective and repeatable method for evaluating welfare that can be applied to invertebrates in zoological collections. Recently introduced into zoological collection management is the Animal Welfare Assessment Grid (AWAG). The AWAG helps to identify negative and positive welfare states, through assessing animal- and environmental-based indicators to make changes that lead to a better quality of life. Originally developed for the assessment of laboratory primates, the system has been successfully adapted to assess a variety of taxa across different environments, facilitated by the development of cloud-based software. In this study, the AWAG has been adapted to assess the cumulative lifetime experience of captive decapods and cephalopods at two different institutions, Marwell Zoo and National Marine Aquarium. This study has provided further evidence that the AWAG is adaptable and demonstrates the first time any objective scoring system has been successfully adapted for use in invertebrates. Through graphical representation, the results show that the AWAG identifies changes in welfare scores that can be attributed to specific events and can be used to predict the future vulnerability of species to welfare changes and suggest alternative management methods. This monitoring tool provides a versatile method of implementing practical welfare monitoring in zoos and aquariums.
... Humans are not the only ones to face stress. Although this may seem trivial from today's perspective, soil invertebrates such as isopods may also suffer from stress (Elwood et al. 2009). They have to solve existential problems to fulfil their necessities, such as the need for water or moisture (Cloudsley-Thompson 1956), food (Brody and Lawlor 1984), shelter (Allee 1926), and mating (Sutton 1972). ...
... Just like vertebrates, invertebrates respond to stress caused by changes in the environment with a stress reaction. Isopods secrete substances into the haemolymph which are similar to glucocorticoids that can be found in vertebrates (Elwood et al. 2009). Stress can also shorten the maternal care period of the clutch (Kight and Nevo 2004). ...
This study was focused on behaviour of the Common Rough Woodlouse ( Porcellio scaber ) and the Plum Woodlouse ( Porcellionides pruinosus ) under the influence of stressors in the form of increased temperature, the vibrating surface, or their combination. Two types of experiments were performed. First, woodlice placed in a labyrinth were observed, to determine the degree of turn alternation, the speed of passing through the labyrinth, and the corrections of turn alternation, when exposed to stressors. In the second experiment how woodlice aggregate in the aforementioned potential stressors was recorded and whether the change in aggregation behaviour can be an indicator of the degree of stress. Increased temperature and the combination of increased temperature and vibrations were stressors only for P. scaber . The results show that vibrations are not a stress factor for P. scaber or P. pruinosus . Porcellio scaber passed through the labyrinth more slowly at increased temperatures, and although they made more turn-corrections, they alternated turns less intensely. Its aggregation behaviour was mainly influenced by temperature, which confirms that the aggregation behaviour of P. scaber actually indicates a degree of stress.
... Cunningham et al. (2021b) also observed alterations of various aspects of defence and attack with regard to 'rapping contests' (which is the acquisition of an already occupied shell from another hermit crab) in Pagurus bernhardus individuals exposed to microplastics. Changes in behavioural patterns due to toxicants are thus linked to physiological alterations as detailed in the previous sections and can manifest as stressful or painful circumstances in crustaceans (Elwood et al., 2009;Hebel et al., 1997). Thus, microplastics could affect behaviours such as foraging, predation, mating, fighting and even swimming which could lead to a weakened state of the animal (Barboza et al., 2018;Crooks et al., 2019). ...
... In spite of all the information available on microplastics in Decapods, a number of other tests/studies could be conducted to fully understand microplastic toxicity. For example, the effects of microplastics on the crustacean hyperglycemic hormone (CCH), which is the equivalent of the vertebrate stress hormone cortisol and corticosterone (Elwood et al., 2009) have not been evaluated. This hormone has been used as an indicator of stress in Decapod crustaceans Guo et al., 2021;Lorenzon et al., 2004). ...
The presence of microplastics in the aquatic environment poses a serious threat not only to aquatic organisms but also to human beings that consume them. The uptake and effects of microplastics have been studied in almost all groups of aquatic organisms. This review details the different aspects of microplastics exposure in an ecologically and economically important group of crustaceans, the Decapods. A majority of Decapod crustaceans such as prawns, shrimp, crabs, lobsters and crayfish are consumed as seafood and play important roles in food chains and food webs. Numerous studies are available on the accumulation of microplastics in tissues such as the gills, hepatopancreas and gastrointestinal tract in these organisms. Experimental studies have also highlighted the toxic effects of microplastics such as oxidative stress, immunotoxicity and reproductive and developmental toxicity in them. This review also summarizes the ecological impacts and implications in human beings as well as lacunae with regard to microplastic uptake in Decapods.
... A stronger argument for a more inclusive ethics than the mere existence of advanced cognition (Vallortigara 2017(Vallortigara , 2020 is provided by the handful of recent studies investigating metacognition (Perry & Barron 2013), emotion-like states (Perry et al. 2016; but cf. Baracchi et al. 2017), sentience ) and pain (Elwood et al. 2009;Gherardi 2009;Elwood 2011) in Pancrustacea. Empirical studies and cognitive theorists have begun to support the existence of very basic forms of consciousness, such as subjective experience in invertebrates. ...
... There is evidence that positive or negative emotions can be induced in some invertebrates and that these affect their judgment (Bateson et al. 2011;Perry & Barron 2013;Fossat et al. 2014;Gibson et al. 2015). Crustaceans may feel pain (Elwood et al. 2009;Gherardi 2009;Elwood 2011), and the behavioral and physiological responses of crayfish to electric shocks are analogous to those of mammals, suggesting that they might experience fear (Fossat et al. 2014). ...
... However, the brains of crabs and lobsters are likely to be larger than those of many vertebrates. Broom (2007) [15] and [76] noted that brain size does not necessarily equate to complexity of function, as shown by the cognitive abilities of bees [77]. The brains of decapods are surprisingly complex [78], with different areas showing clear functional separation, and they enable complex behaviour [33]. ...
Early discussions about possible pain in crustaceans often comprised speculation and anecdotes. Experiments to investigate pain took guidance from these early debates, and from studies on other taxa. Many experiments provided data that are consistent with the idea of pain. However, that does not mean that pain has been proved, but they open the possibility. With each study that is consistent with pain being felt, the probability increases, but we will probably never have conclusive proof. Some responses appear to be nociceptive reflexes; however, they at least indicate that the animal responds to stimuli such as tissue damage, heat, acid, alkaline, or electric shock. The data are said to be consistent with pain only if they cannot be explained by reflexes. These studies have encouraged various organisations to improve the welfare of crustaceans, e.g., PETA, Crustacean Compassion, RSPCA, British Veterinary Association, UFAW, and HSA. They also formed much of the evidence included in the highly influential review of sentience for the UK government that resulted in the inclusion of decapod crustaceans in the Animal Welfare (Sentience) Act 2022. This recognises that decapod crustaceans are sentient. By contrast, the New York Declaration recognises there is a possibility of sentience. Others have argued against the idea of pain in crustaceans. Nevertheless, the 2022 Act provided an impetus to groups that campaign for improved welfare. Some UK retailers now require improved slaughter techniques for the shrimp/prawn they sell, and electrical stunning is the preferred slaughter method.
... Ethical considerations revolve around insects' sentience and ability to suffer. While insects are commonly thought to be less sentient than mammals and birds, some study suggests they may be capable of feeling pain and distress (Elwood et al. 2009). This raises concerns regarding the humane treatment of insects in farming and processing. ...
This comprehensive analysis examines insects' potential as sustainable food and feed sources, focusing on various scholarly views and empirical studies. Edible insects offer a viable answer to global food security issues because of their high nutritional content, efficient feed conversion rates, and lesser environmental effects when compared to traditional cattle. Nutrient composition investigations show that insects are high in proteins, vitamins, and minerals, making them acceptable for human and animal diets. Consumer acceptability surveys show that western countries are becoming more open to entomophagy, yet cultural hurdles still exist. Life cycle assessments show that insect farming benefits the environment by reducing greenhouse gas emissions and water footprints. Safety assessments confirm the possibility of introducing insects into food systems if strict requirements are followed to reduce microbial hazards. Economic analyses indicate that the sale of insects can improve livelihoods and contribute to sustainable agriculture. Despite the potential benefits, more study is required to solve regulatory, ethical, and consumer perception issues before completely integrating insects into global food systems. Research is needed to establish optimal farming methods, strengthen food safety, understand the health impacts of consumption, explore consumer acceptance, tackle ethical considerations, and investigate economic viability. This review emphasized the necessity for multidisciplinary approaches to promote entomophagy and harness its potential for a sustainable future.
... There is strong evidence indicating the ability of these animals to experience pain, particularly crabs, lobsters, and crayfish . They experience suffering and are aware of the location of pain (Barr et al., 2008;de Souza Valente, 2022b;Elwood et al., 2009;Gherardi, 2009). Most decapods exhibit decision-based behaviour (denoting reasoning capacity), respond to analgesics and anaesthetics, protect injured body parts (protective response), and present prolonged behaviour modification when subjected to painful stimuli (de Souza Valente, 2022a; Sneddon et al., 2014). ...
The ethical debate on the moral consideration of non-human animals (hereafter animals) is currently centred on the evidence of sentience in these individuals. Legal protection for vertebrates and cephalopods (and decapods in the UK) has resulted from the recognition of sentience in these animals. Although one should celebrate the significant advances in the legal protection of animals in recent decades, current animal legislation is modulated by an instrumental viewpoint, remaining speciesist and anthropocentric. A sentient being is here understood as one who has the phenomenological experience of awareness, which is the most basic sense of phenomenal consciousness that implies the existence of a subject who is not indifferent to what happens to itself. This paper demonstrates, with reasonable assumptions, that this concept of sentience would apply to many invertebrate species, thus deeming them worthy of increased moral consideration and legal protection. In cases in which sentience cannot be demonstrated clearly, one should assume the precautionary principle and consider the intrinsic value of each animal to designate moral consideration. In considering sentience as the primary condition for moral consideration, science must expand who is recognized as sentient rather than being reductionist. Animal ethics must review to whom the moral consideration should be given. Animal legislation must include legislative innovations and invertebrates in its protective scope. Thereby, a significant improvement in the current political and legislative decisions would be rooted in animal ethics. Opening the ethical perception and broadening the debate are urgent, as moral consideration should be given to all animals.
... Injured crustaceans exhibit behaviours such as rubbing, limping, or caring for the affected area, suggesting awareness of the injury and attempts to minimise damage [37,[101][102][103]. Autotomy, or the shedding of a limb, has been interpreted as a response mediated by an experience similar to pain [104][105][106]. Behavioural changes consistent with an increased state of anxiety after exposure to aversive stimuli have been observed in crayfish, indicating changes in emotional state that were attenuated by anxiolytic drugs, suggesting mechanisms of anxiety similar between crustaceans and humans [107][108][109]. ...
The rapid growth of shrimp farming, particularly of Penaeus vannamei, accounts for about 80% of the global production of farmed shrimp and involves the cultivation of approximately 383 to 977 billion individuals annually, which highlights the urgent need to address the ethical and technical implications of raising potentially sentient beings. This study builds on the state-of-the-art assessment of sentience, consciousness, stress, distress, nociception, pain perception, and welfare to adapt the General Welfare Index (GWI) for farmed shrimp. The GWI is a quantitative index developed by our research group to measure the degree of welfare in aquaculture, and it has been previously applied to grass carp and tilapia. Using the PRISMA methodology and the creation of a hypothetical shrimp farm, the GWI, with 31 specific and measurable indicators across various welfare domains, is adapted to P. vannamei, offering a comprehensive assessment framework. The inclusion of quantitative welfare indicators promises to improve living conditions in alignment with legislation adopted on decapods’ sentience and contemporary scientific advances.
... Despite the growing body of research on Neocaridina davidi, there was no available data on their sedation when the project was started. Since such conditions as close confinement as well as rapid temperature changes can elicit a stress response in Crustaceans [13], there was a need to create a sedation protocol for shrimps that would participate in the rocket flight. Therefore, basing on the literature, eugenol was established as the most promising anaesthetic as it has been successfully used over different shrimp species before, for instance, Macrobrachium rosenbergii [14], Palaemonetes sinensis [15], Penaeus monodon [16] or Litopenaeus vannamei [17]. ...
This paper presents the history, as well as scientific and engineering value of the SHREAMP 2.0 (Space Habitat Research-Effectiveness of Anesthetics Monitoring Payload)-a project aiming at finding a safe way to transport Neocaridina davidi shrimps in a sounding rocket. Shrimps, as aquatic animals, might one day become a part of extraterrestrial aquaponics systems and help provide food for the future Moon and Mars settlers. The project was developed by members of the AGH Space Systems Student's Association in 2021. It flew on a second attempt at Spaceport America Cup 2023. Although it did not come back in one piece, the results achieved during its development are worth mentioning, particularly the electronic design and the research done on shrimp sedation.
... footnote 2). For insects, there is certainly discussion about whether they are sentient, as there is for crustaceans and cephalopods (Elwood et al. 2009: 128-136, Elwood 2011: 175-184, Mikhalevich and Powell 2020. However, the discussion we are joining concerns vertebrates such as American pika (Palmer 2016) or the Alpine marmot (Marmota marmota) as a European counterpart, the Florida panther (Puma concolor coryi) or the Iberian lynx (Lynx pardinus), pangolins (Pholidota spp.), Komodo dragons (Varanus komodoensis), moor frogs (Rana arvalis), and sharks (Selachimorpha spp.). ...
The use of genetic engineering is increasingly discussed for nature conservation. At the same time, recent animal ethics approaches debate whether humans should genetically engineer wild animals to improve their welfare. This paper examines if obligations towards wild sentient animals require humans to genetically engineering wild animals, while arguing that there is no moral need to do so. The focus is on arguments from animal ethics, but they are linked to conservation ethics, highlighting the often neglected overlap between the two fields. The paper emphasizes that a) the benefits of genetic engineering are overestimated
and at the same time harms from its development and use underestimated, b) the assumption that genetic engineering is an appropriate ‘last resort’ tool is wrong, c) many arguments in favor of genetic engineering are based on an inadequate understanding of ecology and bio-technological processes, and d) the debate downplays the importance of self-determination for wild animals.
... This increases serotonin availability at the synaptic cleft, leading to enhanced serotonergic neurotransmission, which regulates mood, sleep, appetite, and other physiological processes. Crustacea may exhibit locomotor activity and exploration behavior enhanced by higher serotonin levels due to increased levels of the crustacean hyperglycemic hormone (Elwood et al., 2009). Based on the current study and previous results, crayfish boldness and activity are observed to be increased after SSRI exposure. ...
The freshwater crayfish, Procambarus clarkii is an excellent aquatic animal model that is highly adaptable and tolerant. P. clarkii is widely used as a toxicity model to study various pharmaceutical exposure. This animal model has complex behavioral traits and is considered sensitive to environmental changes, making it an excellent candidate to study psychoactive drugs based on a behavioral approach. However, up to now, most behavioral studies on crayfish use manual observation and scoring that require panelists. In this study, we aim to develop an automation pipeline to analyze crayfish behavior automatically. We use a deep-learning approach to label body parts in multiple crayfish, and based on the trajectory results, the intra-or inter-individual crayfish were calculated. Reliable and fast results of several behavior endpoints in multiple crayfish were retrieved. We then validated the detection performance of numerous crayfish in specific gender groups (male-male and female-female). Based on the result, the male crayfish displayed significantly higher aggression than females. We also tested the antidepressant exposure on this animal model to evaluate the psychoactive effects of this drug. As male crayfish display more distinct agonistic behavior than females, we exposed them to sertraline (SRT) 1 ppb for 7 and 14 days. It was revealed that sertraline was able to alter several behavioral endpoints in crayfish. Significant increases in extend claw ratio, total distance moved, average speed, and rapid movement were displayed in sertraline-exposed crayfish but decreased interaction time and longest interaction time. In addition, SRT 14 days exposure could atler the aggressiveness and bold behavior In the present method, DeepLabCut (DLC) has been utilized to analyze the locomotion behavior of multiple crayfish. This established method provides rapid and accurate ecotoxicity measurements using freshwater crayfish, which beneficient and applicable for environmental research.
... 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.
... Singer (1975Singer ( , 1993 expands this approach by including moral considerations for using and killing animals for human ends. Given that aggregate pleasure and pain are central to utilitarianism, it includes all sentient beings, and therefore all vertebrate animals (mammals, fish, birds, reptiles, and amphibians), as well as crustaceans and octopuses (Elwood et al. 2009). ...
Companies have a strong moral responsibility towards animals. Consumers, investors and NGOs are becoming more critical of the treatment of animals by companies. Nevertheless, the topic of animal ethics seems to be a blind spot in the corporate social responsibility policies of most companies. As moral actors, companies should take the interests of animals into account in their decisions. More specifically this means that companies should take the current and future welfare of animals into account, including continuation of their lives. Based on this corporate responsibility, critical reflection is offered on various categories of corporate impact on animals. The chapter concludes with managerial implications for different industries.KeywordsAnimals and businessMoral statusRight to lifeFive FreedomsLivestockEntertainment industryAnimal testing
... Research on nociception in animals has considerably advanced, today the scientific consensus recognizing the capacity to suffer for every species of Mammals and birds (Recognition and Alleviation of Pain in Laboratory Animals p. 21). There is also nociception evidence regarding fishes (Sneddon et al. 2003) and crustaceans (Elwood et al. 2009). ...
Ex vivo systems are under increasing interest for bioethical, legal and financial stakes. To study muscle function and regeneration, medical research requires functional analysis platforms for mature myotubes and unconventional muscle stem cells (MuSCs) culture tools integrating mechanical consraints. During my doctoral works, a 3D myotube culture chip with contraction monitoring capacity has been developed. Combining photopatterning technology and microsubstrate design allowed to obtain high culture yield in controlled physical and chemical microenvironment. Spontaneous contractions of human primary myoblast-derived 3D myotubes has been observed, their generated forces measured and their contraction pattern characterised. The impact of 3D culture on nuclear morphology has been analysed, confirming organizational similarities betaween obtained 3 myotubes and in vivo myofibers. Moreover, LMNA-related Congenital Muscular Dystrophy has been modelled in 3D mutants myotubes displaying typical laminopathy phenotype. Finally, MuSCs has ben cultured on hydrogels, demonstrating the effect of niche elasticity variations on MuSCs activation during muscle regeneration.
... Indicators for phenomenal consciousness include the presence of nociceptors, opioid receptors, and a central nervous system, certain behaviors, and evolutionary considerations. A quick look at the relevant scientific literature and three recent reviews by biologist Donald M. Broom and philosophers Joel P. MacClellan and David DeGrazia suggests that mammals and birds almost certainly, and amphibians, reptiles, fish, decapod crustaceans, and cephalopods likely have the capacity for phenomenal consciousness, but probably not insects (Sarjeant 1969;Wells 1978;Gould and Gould 1982;Eisemann et al. 1984;Smith 1991;Gentle 1992;Machin 1999;Sneddon, Braithwaite, and Gentle 2003;Chandroo, Duncan, and Moccia 2004;Elwood, Barr, and Patterson 2009;Braithwaite 2010;Elwood 2011;Mosley 2011;MacClellan 2012, 180 ff.;Broom 2014, 122;DeGrazia 2020). 43 On my view, that makes relevantly normal, developed members of these taxonomic classes intrinsically valuable subjects of experience whom it is no less seriously wrong to kill as it is to kill you or me, other things being equal. ...
According to a diverse and widely popular family of moral theories, there is a class of individuals – typically humans or persons – who have the very same, full moral status. Individuals not falling into that class count for less, or not at all, morally speaking. In this article, I identify two problems for such theories, the mapping problem and the problem of misgrounded value, and argue that they are serious enough to be decisive. I will then propose an alternative account of full and equal moral status that avoids those problems. In grounding full moral status in phenomenal consciousness, it preserves the idea that you and I are equal, but at the same time radically expands the community of moral equals. I conclude by discussing some practical implications of my proposal.
... As a stress indicator, cortisol is correlated to mortality and growth suppression (Tataranni et al., 1996). In crustaceans, the crustaceans hyperglycemic hormone (CHH) secreted by X-organ and sinus gland complex (XO-SG) has similar effects than cortisol and corticosterone, by regulating the conversion of glycogen into glucose (Elwood et al., 2009;Liu et al., 2019). Although CHH and MIH are different in structure, yet they appear to have similar functions in inhibiting ecdysteroid synthesis (Chung and Webster, 2003). ...
An 8 weeks trial was performed to test the effects of light spectra [full-spectrum, violet (405 nm), blue (470 nm), cyan (500 nm), green (525 nm), yellow (570 nm), and red (625 nm)] on growth performance, molting, antioxidant capacity, stress response and expression of molting, and apoptosis-related genes in Scylla paramamosain. Results showed that spectrum had a significant effect on S. paramamosain physiology. Compared to blue light, crabs exposed to violet light had a significantly lower survival rate (79.5 ± 3.6% vs. 94.9 ± 3.6%), weight gain (49.2 ± 5.4 vs. 67.6 ± 6.7), molt frequency (4.2 ± 0.2 vs. 4.5 ± 0.1), and extended intermolt intervals between instar 1 and 2 stages (C1–C2) (6.3 ± 0.3 vs. 5.0 ± 0.1 days). Expression of the molt-inhibiting hormone (mih) gene was upregulated in crabs reared under violet light. According to the regression analysis, maximum SGR would be at 449.97 nm. Crabs exposed to blue light also had lower melatonin levels than under full-spectrum and lower cortisol levels than violet and yellow groups. Regarding oxidative stress, crabs in full-spectrum had lower H2O2 and MDA contents, however, no significant difference was found in total antioxidant capacity (T-AOC), superoxide dismutase (SOD), and catalase (CAT) in hepatopancreas from crabs under different spectra. Gene expression of hsp40, hsp70, hsp90 were down-regulated in crabs exposed to the full-spectrum light group. Regarding apoptosis-related genes, bcl-2 gene expression in crabs under cyan and the cox IV and caspase 3 in green were upregulated, suggesting cyan light may inhibit, while green light may promote apoptosis. Taken together, these results suggest that blue or cyan light would promote growth performance, while full-spectrum light could reduce stress response in S. paramamosain.
... Different systems from those of vertebrates, similar functions, possibly similar experience of suffering (Elwood et al. 2009) ...
The aim of this paper is to take normative aspects of animal welfare in corporate practice from a blind spot into the spotlight, and thus connect the fields of business ethics and animal ethics. Using insights from business ethics and animal ethics, it argues that companies have a strong responsibility towards animals. Its rationale is that animals have a moral status, that moral actors have the moral obligation to take the interests of animals into account and thus, that as moral actors, companies should take the interests of animals into account, more specifically their current and future welfare. Based on this corporate responsibility, categories of corporate impact on animals in terms of welfare and longevity are offered, including normative implications for each of them. The article concludes with managerial implications for several business sectors, including the most animal-consuming and animal-welfare-threatening industry: the food sector. Welfare issues are discussed, including the issue of killing for food production.
... This is not unique to insects, as similar controversies exist for reptiles, crustaceans and fish (e. g. Braithwaite and Droege, 2016;Elwood et al., 2009;Lambert et al., 2019). ...
Globally, there is increasing pressure to find solutions for feeding the growing human population. One of the proposed answers to this problem is to farm edible insects, both for human consumption and as feed for domesticated livestock. But what do we know about these miniature livestock? Are they capable of suffering, and if so, what does this mean for this new and growing industry? Here, we review a fraction of what is currently known about insect sentience and cognition, by focusing on a portion of the published scientific literature over the past 31 years (1990-2020). Specifically, our review aimed to (1) assess the extent to which insect sentience and cognition featured in a selection of the scientific literature published between 1990-2020, (2) assess which aspects have been studied, and in which insect taxa, and (3) identify the insect species currently being promoted in policy for farming, and the reasons why edible insects are now on the global policy agenda. We found evidence that many species of insects, across a broad range of taxonomic Orders, are assumed and/or confirmed to be capable of a range of cognitive abilities, and that there is reason to believe that some species may also feel important emotional states such as stress. The market for insects as feed and food is set to become a booming industry in the future, yet our review highlights how we still know very little about the minds of insects and their capacity to suffer in farming systems. We hope that our findings will stimulate additional research and subsequent policy development relating to how insects are farmed in the future, particularly in the context of mitigating any potential negative animal welfare impacts.
... However, studies have largely been limited to those on vertebrates, and few studies have focused on behavioral plasticity in response to threatening experiences in invertebrates, including crustaceans. A number of studies have shown that crustaceans demonstrate fearful/anxiety-like responses to aversive stimuli and situation (reviewed in Elwood et al. 2009;Fossat et al. 2014;Perrot-Minnot et al. 2017). For instance, crabs (Chasmagnathus granulatus) presented with a novel stimulus, such as a moving shadow, respond by escape running (i.e., fearful response), and this escape response is reduced by morphine injection (Maldonado et al., 1989). ...
Behavioral variation in animals is often influenced by experience. Previous studies have found that daily threatening experiences can enhance fear- and anxiety-like behaviors in some vertebrates. However, it is unclear whether the change in fear/anxiety behavior occurs in invertebrates. The present study investigated whether fear/anxiety behavior could be affected by a net-chasing treatment in two shrimp species (Neocaridina denticulata ssp. and Palaemon pacificus). The net-chasing treatment was repeated for 8 days to simulate daily predator experiences, and behavioral tests (open-field, shelter-seeking, and escape-response tests) were conducted on the day following the last day of treatment. Net-chased N. denticulata ssp. displayed a tendency to remain near a wall compared with the control in the open-field test, whereas net-chased P. pacificus shrimps demonstrated greater escape behavior compared with the control in the escape-response test. These results suggest that fear/anxiety behavior for both shrimp species can be affected by the net-chasing treatment, although the pattern of behavioral change differed between the two species. The findings suggest that daily threatening experiences change the behavior of shrimp and cause them to select a regular avoidance strategy when they encounter risks and unknown situations.
... Investigation of the potential stress of handling decapod crustaceans during experimentation will likely become more pertinent in the coming years. Recently, there has been debate regarding if/how decapod crustaceans experience pain and stress, and there is continuing discussion about re-classifying them as 'animals,' thereby requiring animal welfare protocols for scientific experiments (Elwood et al. 2009;Stevens et al. 2016;Weineck et al. 2018;Diggles 2019;Drinkwater et al. 2019;Elwood 2019). ...
Stress due to handling is often an unavoidable feature of experimental investigations. In some cases, appropriate settling times are not considered, and as such, physiological responses caused by handling may become additive with those of experimental treatments. This study investigated the effect of different handling procedures on the acute physiological responses of green shore crab (Carcinus maenas). Handling, such as would occur during transport around a research facility or transfer during experimental procedure, was designated as light (10 min emersion) or severe (10 min emersion with shaking). Oxygen consumption (MO2) and haemolymph glucose and haemolymph L-lactate concentrations were elevated post-handling, the magnitude of the change related to the severity of handling stress. Glucose and L-lactate concentrations peaked within 1 h and returned to basal levels within 6 h, but MO2 remained elevated for 10 h, reflecting the additional energy required to oxidize L-lactate and replenish energy reserves. Differences between light and severe handling treatments showed that vibration (shaking) was a major contributor to the stress response, rather than the experimental emersion. This was confirmed in a second experiment where crabs were handled without emersion, and MO2 remained elevated for 14 h. In this experiment, the most pronounced increase in MO2 and metabolic parameters occurred in crabs that were physically touched and moved rapidly from the holding to experimental tanks. Here the touch, as well as vibration and visual stimuli, provoked a fight-flight response in the crabs. Stress responses were also evident in crabs gently transferred by containers. The fact that transferring crabs with no physical touching and minimal visual and vibrational stimuli still evoked a stress response, albeit less pronounced, supports a recommendation that crustaceans should be left to settle in the apparatus for at least 12 h after handling before experimental procedures are initiated.
... Shrimp trials and experiments in this study were approved by the Institutional Animal Care and Use Committee of the National Center for Genetic Engineering and Biotechnology, Thailand (BT-Animal 28/2560). All experiments were performed in accordance with Animal Research: Reporting of In Vivo Experiments (ARRIVE) and conformed with international and national legal and ethical requirements [28,29]. ...
Cyclooxygenase (COX) is a two-step enzyme that converts arachidonic acid into prostaglandin H2, a labile intermediate used in the production of prostaglandin E2 (PGE2) and prostaglandin F2α (PGF2α). In vertebrates and corals, COX must be N-glycosylated on at least two asparagine residues in the N-(X)-S/T motif to be catalytically active. Although COX glycosylation requirement is well-characterized in many species, whether crustacean COXs require N-glycosylation for their enzymatic function have not been investigated. In this study, a 1,842-base pair cox gene was obtained from ovarian cDNA of the black tiger shrimp Penaeus monodon. Sequence analysis revealed that essential catalytic residues and putative catalytic domains of P. monodon COX (PmCOX) were well-conserved in relation to other vertebrate and crustacean COXs. Expression of PmCOX in 293T cells increased levels of secreted PGE2 and PGF2α up to 60- and 77-fold, respectively, compared to control cells. Incubation of purified PmCOX with endoglycosidase H, which cleaves oligosaccharides from N-linked glycoproteins, reduced the molecular mass of PmCOX. Similarly, addition of tunicamycin, which inhibits N-linked glycosylation, in PmCOX-expressing cells resulted in PmCOX protein with lower molecular mass than those obtained from untreated cells, suggesting that PmCOX was N-glycosylated. Three potential glycosylation sites of PmCOX were identified at N79, N170 and N424. Mutational analysis revealed that although all three residues were glycosylated, only mutations at N170 and N424 completely abolished catalytic function. Inhibition of COX activity by ibuprofen treatment also decreased the levels of PGE2 in shrimp haemolymph. This study not only establishes the presence of the COX enzyme in penaeid shrimp, but also reveals that N-glycosylation sites are highly conserved and required for COX function in crustaceans.
... These include ACTH and cortisol-like molecules such as those that have been detected in the hemocytes of various molluskan species and research indicates that their stress-response is similar to that of vertebrates (Ottaviani, 2006). Crustacean hyperglycemic hormone (CHH) is thought to be the crustacean equivalent of cortisol and corticosterone (Elwood, Barr, and Patterson, 2009). ...
The use of full spectrum illumination, including ultraviolet (UV), during captive husbandry of arachnids is common practice. The effect of this on captive arachnids has not been previously investigated. Comparison of key behavioral changes and hemolymph cortisol immunoreactivity was undertaken with and without full spectrum lighting. King baboon spiders, Pelinobius muticus and Indian giant scorpions, Heterometrus swammerdami were selected for the study. Both organisms spent all their time hidden when exposed to full spectrum light compared to low-level ambient light except for one instance. There was no significant difference in burrowing and webbing in P. muticus when exposed to full spectrum lighting. There was a decrease in the number of behaviors or postures expressed in full spectrum lighting compared to ambient light for both species. Cortisol immunoactivity of both species were significantly elevated after exposure to full spectrum lighting. This study provides the first evidence of detectable cortisol immunoactivity in arachnid hemolymph. These levels changed in response to full spectrum illumination and were linked to behavioral changes. This suggests that a common husbandry practice may be detrimental to arachnids.
... There are no minimal animal care requirements for decapods in the European legislation [47]. They have long been regarded as not being sentient and unable to experience pain or suffering because they were thought to respond to noxious stimuli purely by nociceptive reflex [48,49]. ...
Simple Summary
Current European legislation that protects animals used for scientific purposes excludes decapod crustaceans (for example, lobster, crab and crayfish) on the grounds that they are non-sentient and, therefore, incapable of suffering. However, recent work suggests that this view requires substantial revision. Our current understanding of the nervous systems and behavior of decapods suggests an urgent need to amend and update all relevant legislation. This paper examines recent experiments that suggest sentience and how that work has changed current opinion. It reflects on the use of decapods as models in biomedical research and in ecotoxicology, and it recommends that these animals should be included in the European protection legislation.
Abstract
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.
The last quarter century has produced a remarkable amount of scientific research on the data-rich and immensely important American lobster (Homarus americanus). In fact, more than 1000 peer-reviewed papers have been published on the species since 2000, advancing all aspects of lobster science, research, and management. Many of these efforts have been motivated by large-scale alterations in ecosystems in the Northwest Atlantic due to climate change, including changes in temperature, water chemistry, ecosystem productivity, and oceanography. These changes have driven researchers to focus on the many direct and indirect impacts that climate change has had on the most valuable single-species fishery in North America. The goal of this review is to provide a summary of the major findings in lobster science over the last quarter century, with an emphasis on how anthropogenic impacts and environmental modifications might impact lobsters and the lobster fishery in the future as well as to serve as a touchstone for the next 25 years within the context of a dynamic and changing ecosystem. This review also includes a summary of important topics and ideas for further research, especially those with knowledge gaps, in the hope that it can help guide future approaches to American lobster research and further improvements to fisheries management.
Cultivated crustacean meat (CCM) is a means to create highly valued shrimp, lobster, and crab products directly from stem cells, thus removing the need to farm or fish live animals. Conventional crustacean enterprises face increasing pressures in managing overfishing, pollution, and the warming climate, so CCM may provide a way to ensure sufficient supply as global demand for these products grows. To support the development of CCM, this review briefly details crustacean cell culture work to date, before addressing what is presently known about crustacean muscle development, particularly the molecular mechanisms involved, and how this might relate to recent work on cultivated meat production in vertebrate species. Recognizing the current lack of cell lines available to establish CCM cultures, we also consider primary stem cell sources that can be obtained non-lethally including tissues from limbs which are readily released and regrown, and putative stem cells in circulating hemolymph. Molecular approaches to inducing myogenic differentiation and immortalization of putative stem cells are also reviewed. Finally, we assess the current status of tools available to CCM researchers, particularly antibodies, and propose avenues to address existing shortfalls in order to see the field progress.
Τὰ ἔντομα χρησιμοποιοῦνται ὡς ζῶα ἐργαστηρίου σὲ πληθώρα ἐρευνῶν στὶς βιοἐπιστῆμες. Πάραυτα, ἐν ἀντιθέσει μὲ τὰ σπονδυλωτὰ ζῶα ἐργαστηρίου ἀλλὰ καὶ ὁρισμένα μαλάκια, ἠ ἠθικὴ τῆς χρήσεως τῶν ἐντόμων στὴν ἔρευνα καὶ ἡ εὐημερία τους δὲν εἶναι ἀντικείμενο ὑψηλῆς σημασίας στὰ περισσότερα ἐργαστηριακὰ πρωτόκολλα ἀλλὰ καὶ δὲν ὁρίζεται ἀπὸ τὴ Νομοθεσία.
Παρότι ἀποτελοῦν τὴν πολυπληθέστερη ὁμάδα στὸν πλανήτη, αὐτὰ φαίνεται νὰ εἶναι ἀδιάφορα ἀπὸ φιλοσοφικὴ σκοπιὰ ὡς πρὸς τὴν ἠθική τους σημασία, σὲ ἀντίθεση μὲ ἄλλα ζῶα. Οἱ παραδοσιακὲς φιλοσοφικὲς θεωρίες δὲν καταπιάνονται μὲ τὴν περίπτωσή τους, ἐνῶ οἱ βιοκεντρικὲς καὶ οἰκοκεντρικὲς θεωρίες εἶναι αὐθαίρετες, δεχόμενες τὴν ἐγγενὴ ἀξία τους ἀξιωματικά, κάνοντας ἀδύνατη τὴ δικαιολόγησή τους. Ὁ μεγάλος ἀριθμός τους συναρτήσει μὲ τὸ μικρό μέγεθός τους, σὲ συνδυασμό μὲ τὴν ἀβεβαιότητα ὡς πρὸς τὴν ἱκανότητά τους νὰ βιώνουν πόνο, δημιουργοῦν πολλὰ κενὰ στὴν προσπάθεια ἠθικῆς δικαιολογήσεως τῶν πράξεών μας ποὺ ἀφοροῦν τὰ ἔντομα.
Στὴν παρούσα διατριβὴ ἐπιχειρεῖται ἡ θεμελίωση μιᾶς δεοντοκρατικῆς ἠθικῆς θεωρίας γιὰ τὴ συμπεριφορά μας στὰ ἔντομα. Γίνεται προσπάθεια ἀναγνωρίσεως τῆς ἠθικῆς τους σημασίας καὶ ϋπολογισμοῦ τῆς ἠθικῆς τους σπουδαιότητος, καθὼς καὶ ἡ κατάταξή τους στὴν ἠθικὴ σφαίρα μαζὶ μὲ τὶς ὑπόλοιπες ἠθικῶς σημαίνουσες ὀντότητες.
Μὲ τὴν ἀναγνώριση τῆς ἠθικῆς σημασίας τῶν ἐντόμων, ἀναπτύσσονται τὰ βιοηθικὰ ζητήματα ποὺ ἐγείρονται κατὰ τὸν πειραματισμὸ μὲ ἔντομα καὶ ἐπιχειρεῖται νὰ ἀπαντηθοῦν τὰ ὅποια ἐρωτήματα στὰ πλαίσια τοῦ νέου δεοντοκρατικοῦ κανονιστικοῦ πλαισίου.
Three decades ago, M. A. K. Halliday, the founder of systemic functional linguistics (SFL), presented a paper to AILA in Greece entitled 'New Ways of Meaning: A Challenge to Applied Linguistics' (Halliday, 1990), which introduced the notion of an ecological study of language (Fill and Mühlhäusler, 2001). In this seminal paper, Halliday emphasizes that 'language does not passively reflect reality; language actively creates reality' (cf. Halliday and Matthiessen, 1999) and that 'lexi-cogrammar… shapes experience and transforms our perceptions into meanings' (Halliday, 1990: 65). He identifies three 'problematic spheres' as foreseeable challenges language planning, the register of scientific discourse and of language and prejudice, involving the deployment of resources within the system that constructs sexism, racism, growthism, and classism; and highlights the role of future applied linguists-'to use our theory of grammar… as a metatheory for understanding how grammar functions as a theory of experience' (1990: 69) and 'to learn to educate five billion children … at such a time it is as well to reflect on how language construes the world' (1990: 91), one that contains numerous ecosystems essential to the human survival.
Hermit crabs (Paguroidea; Latreille 1802) offer great opportunities to study animal behaviour and physiology. However, the animals’ size and sex cannot be determined when they are inside their shell; information crucial to many experimental designs. Here, we tested the effects of the two most common procedures used to make crabs leave their shells: heating the shell apex and cracking the shell with a bench press. We compared the effects of each of the two procedures on the metabolic rate, hiding time, and duration of the recovery time relative to unmanipulated hermit crabs. The hermit crabs forced to abandon their shell through heating increased their respiratory rate shortly after the manipulation (1 h) and recovered their metabolic rate in less than 24 h, as occurs in individuals suddenly exposed to high temperatures in the upper-intertidal zone. Hermit crabs removed from their shells via cracking spent more time hiding in their new shells; this effect was evident immediately after the manipulation and lasted more than 24 h, similar to responses exhibited after a life-threatening predator attack. Both methods are expected to be stressful, harmful, or fear-inducing; however, the temperature required to force the crabs to abandon the shell is below the critical thermal maxima of most inhabitants of tropical tide pools. The wide thermal windows of intertidal crustaceans and the shorter duration of consequences of shell heating compared to cracking suggest heating to be a less harmful procedure for removing tropical hermit crabs from their shells.
Decapod crustaceans (crabs, hermit crabs, lobsters, crayfish, shrimps, prawns) are sentient beings, not only responding to noxious stimuli but also being capable of feeling pain, discomfort, and distress. General anaesthesia aims at producing analgesia, immobilization, and unconsciousness, while sedation reduces consciousness, stress, and anxiety, though without analgesia. Anaesthesia is recommended to ensure animal welfare and suppress nociception, pain, and suffering in painful and distressing practice that impairs decapods’ welfare. These include long term restrain, surgical procedures, pain control, examination, diagnostic, sampling, treatment, transportation, and euthanasia. The necessary anaesthetic depth, from sedation to surgical anaesthesia, depends on the procedure type. Anaesthetic bath and injection are commonly used, besides inhalation, local anaesthesia, and intracardiac injection. Agents used for the anaesthetic bath include eugenol, isoeugenol, lidocaine, halothane, and essential oils of lemon balm, lemongrass, lemon verbena, and sandalwood. While alphaxalone, eugenol, ketamine-xylazine, lidocaine, morphine, procaine, tiletamine-zolazepam, and xylazine can be used as injectable agents administered on the arthrodial membrane or intramuscular injection. Halothane can be used on inhalation anaesthesia. Local anaesthetics include lidocaine and benzocaine. Notwithstanding, many others are detrimental or ineffective to decapods, thus discouraged. They include but not limited to hypothermia, carbon dioxide, chlorpromazine, chloroform, ethanol, ether, magnesium salts, tricaine methanesulfonate (MS-222), mint and lavender essential oils, passionflower extract, and valerian. Decapods’ welfare, protection, and veterinary attention should not be neglected, but they must receive ethical treatment, including the best of our knowledge and available tools to ensure they are free of pain and discomfort whenever we deal with them.
This chapter deals with the conventional separation of crustaceans and insects. A number of crustaceans are maintained as pets and display animals in marine aquaria, especially shrimp. There are six classes within the subphylum Crustacea: Cephalocarida, Branchiopoda, Ostracoda, Remipedia, Maxillopoda, and Malacostraca. The types of diseases affecting crustaceans are in many cases similar to those affecting aquatic vertebrates and terrestrial mammals. Gas bubble disease is a noninfectious condition in aquatic organisms caused by supersaturated levels of total dissolved gas in water. Shell disease is a common term for areas of erosion and melanization in the exoskeleton in crustaceans. White spot disease is caused by white spot syndrome virus, the only member of the genus Whispovirus . Necrotizing hepatopancreatitis is a newly emerging disease caused by infection with the pathogenic agent Hepatobacter penaei . Hematodiniosis is a fatal disease of crustaceans caused by parasitic dinoflagellates of the genus Hematodinium .
Anthropocentrism and the perceived great dissimilarity of these animals compared to humans also help to explain the lack of concern, aversion, and even fear with which many people regard invertebrates. Concerns for animal welfare in vertebrate livestock production are similar to those for invertebrate production, especially when practiced on a large scale. Resources for information on invertebrate animal husbandry, biology, and medicine are listed in the "Recommended Reading" section. Invertebrate cognitive function is often thought to be limited, resulting in behavioral repertoires consisting primarily of reflexes or preprogrammed patterns. Invertebrates display other intriguing actions in response to stimuli that are believed to cause pain in vertebrate species. Physiological evidence for pain in invertebrates lies primarily with aspects of their neurochemical systems. Euthanasia of any animal should be performed humanely, manifested by providing for minimal pain and distress. A common practice among scientists for invertebrate specimen collection is submersion in a preservative substance.
Sentience is the capacity to have feelings, such as feelings of pain, pleasure, hunger, thirst, warmth, joy, comfort and excitement. It is not simply the capacity to feel pain, but feelings of pain, distress or harm, broadly understood, have a special significance for animal welfare law.
Drawing on over 300 scientific studies, we have evaluated the evidence of sentience in two groups of invertebrate animals: the cephalopod molluscs or, for short, cephalopods (including octopods, squid and cuttlefish) and the decapod crustaceans or, for short, decapods (including crabs, lobsters and crayfish). We have also evaluated the potential welfare implications of current commercial practices involving these animals.
The development of aquaculture is closely related to human life. Crustaceans play essential roles in aquaculture. However, the cultivation of crustaceans has been plagued by various diseases, causing substantial economic losses. At present, the occurrence of shrimp diseases is directly related to environmental stress and physiological dysfunction, and especially environmental stress has become an important factor inducing diseases. Therefore, how to regulate the immune defence of crustaceans under environmental stress has become the primary problem in the prevention and control of shrimp diseases. The neuroendocrine‐immune system plays a vital role in maintaining homeostasis and enhancing environmental adaptability. Besides, in the evolutionary sense, with the theory that the nervous system and the immune system have a common origin put forward, the research on the neuroendocrine‐immune system of invertebrates has gradually become a hot spot. This review describes the evolution and communication mechanism of the neuroendocrine system and immune system in vertebrates and invertebrates, summarizes the characteristics of the neuroendocrine system and immune system in crustaceans, and focuses on how environmental stress affects the regulation of the neuroendocrine system on the immune system in crustaceans, as well as the influence of these regulations on host immune defence. This review also introduced the immune regulation of crustacean intestines under environmental stress and the effect of pathogen stress on crustacean immunity, hoping to lay a theoretical foundation for the follow‐up study of crustacean stress resistance and provide theoretical guidance for the healthy aquaculture of crustaceans.
Soft‐shell crabs are gaining attention internationally as a more lucrative option of selling commercially important portunid species due to their ease of consumption, high nutritional values, and unique and excellent taste. This product, however, is only attainable in captivity as crabs are harvested right after moulting when their exoskeletons are still soft. Among the most crucial factor in soft‐shell crab production is the moult induction method. Shorter moult intervals imply more soft‐shell crabs could be produced, increasing productivity and profit for farmers. This review describes the moulting event, soft‐shell crab production process and production systems, and highlights the currently available and potential moult induction methods, including eyestalk ablation, limb autotomy, the use of ecdysteroid, phytoecdysteroid, biogenic amines and methyl farnesoate, the inhibition of moult‐inhibiting hormone (MIH) and the regulation of physical parameters. This review further compares these moult induction methods and their benefits towards soft‐shell crab production.
Animal models of pain consist of modeling a pain-like state and measuring the consequent behavior. The first animal models of neuropathic pain (NP) were developed in rodents with a total lesion of the sciatic nerve. Later, other models targeting central or peripheral branches of nerves were developed to identify novel mechanisms that contribute to persistent pain conditions in NP. Objective assessment of pain in these different animal models represents a significant challenge for pre-clinical research. Multiple behavioral approaches are used to investigate and to validate pain phenotypes including withdrawal reflex to evoked stimuli, vocalizations, spontaneous pain, but also emotional and affective behaviors. Furthermore, animal models were very useful in investigating the mechanisms of NP. This review will focus on a detailed description of rodent models of NP and provide an overview of the assessment of the sensory and emotional components of pain. A detailed inventory will be made to examine spinal mechanisms involved in NP-induced hyperexcitability and underlying the current pharmacological approaches used in clinics with the possibility to present new avenues for future treatment. The success of pre-clinical studies in this area of research depends on the choice of the relevant model and the appropriate test based on the objectives of the study.
When a passing shadow is presented to the crab (Chasmagnathus granulatus), an escape response is elicited that habituates after repeated stimulation. Results of previous papers suggest that this habituation might be mediated by endogenous opiates, entailing the postulate that opiates may inhibit the response to a danger stimulus. This contention is tested herein. Two trials (T1, T2) of shadow stimulation were given 30 min apart, and the response activity was recorded. In Experiment 1 a range of morphine doses (0, 25, 50, 75, and 100 μg/g) were injected into crabs immediately after T1. Analysis of the M response values showed a morphine dose-dependent reduction in the crab's reactivity to the danger stimulus in T2. In Experiment 2, groups of crabs were injected with 1 of 4 solutions: saline, 70 μg/g morphine, 70 μg/g, morphine plus 1.6 μg/g naloxone, or 1.6 μg/g naloxone. Results suggest that morphine acts through an opiate receptor to inhibit the crab's response level to a danger stimulus. Three possible mechanisms of the morphine effect are discussed, and the most viable one suggests a central site of action.
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. The fact that there is rather similar
evidence of physiological responses, direct behavioural responses and ability to learn
from such experiences so that they are minimised or avoided in future, suggests the
existence of feelings of pain in many species. Indeed the feelings are likely to be an
important part of the biological mechanism for coping with actual or potential
damage. The advantages of pain are that action can be taken when damage occurs,
consequent learning allows the minimising of future damage and, where the pain is
chronic, behaviour and physiology can be changed to ameliorate adverse effects.
Species differ in their responses to painful stimuli because different responses are
adaptive in different species but it is likely that the feeling of pain is much less
variable than the responses. The first steps in the evolution of pain must have
involved cell sensitivity and localised responses but substantial changes in efficacy
could occur once efficient communication within the individual and sophisticated
brain analysis could occur. Changes in the pain system, once there was a moderately
complex brain may well have been slight. Pain is an old system which has probably
changed rather little during vertebrate evolution and pain may be a greater problem in
animals with less cognitive ability. The distinction between pain and nociception
does not seem to be useful.
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.
The morphologies of the cerebral ganglia (brains) of three infraorders of the decapod crustaceans (Astacura-crayfish; Brachyura-crabs; Palinura-spiny lob- sters) are described. A common nomenclature is proposed for homologous nerve roots, brain regions, tracts, com- missures, neuropils, and cell body clusters.
A topical anesthetic and a coagulating agent were employed in this study to determine if observable signs of eyestalk ablation stress could be alleviated in adult female Litopenaeus vannamei broodstock. The experimental design included four separate treatments, with each tested group consisting of 15 female shrimp weighing approximately 40 g. Results show that survival of the shrimp was 100% for all treatments, but reaction to the eyestalk ablation event varied between treatments. Initiation of normal swimming or recovery and the onset of feeding following ablation and treatment also varied among the four groups. The results suggest that the use of a topical anesthetic prior to eyestalk ablation reduces the visible reactions to stress experienced by L. vannamei broodstock, allowing for a more humane eyestalk ablation method.
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.
Studies of the brain inform us about the cognitive abilities of animals and hence affect the extent to which animals of that species are respected. However, they can also tell us how an individual is likely to be perceiving, attending to, evaluating, coping with, enjoying, or disturbed by its environment, and so can give direct information about welfare. In studies of welfare, we are especially interested in how an individual feels. Since this depends upon high-level brain processing, we have to investigate brain function. Brain correlates of preferred social, sexual and parental situations include elevated oxytocin in the para-ventricular nucleus of the hypothalamus. Abnormal behaviour may have brain correlates, for example, high frequencies of stereotypy are associated with down-regulated μ and κ receptors and dopamine depletion in the frontal cortex. Such results help in evaluating the effects of treatment on welfare. Some brain changes, such as increased glucocorticoid receptors in the frontal lobes or increased activity in the amygdala, may be a sensitive indicator of perceived emergency. Active immunological defences lead to cytokine production in the brain, vagal nerve activity and sickness effects. Some aspects of brain function can be temporarily suppressed, for example, by opioids when there is severe pain, or permanently impaired, for example, in severely impoverished environments or during depression. Coping attempts or environmental impact can lead to injury to the brain, damage to hippocampal neurons, remodelling of dendrites in the hippocampus, or to other brain disorganisation. Brain measures can explain the nature and magnitude of many effects on welfare.
Opioid peptides have been revealed in representatives of practically all large taxonomic groups of invertebrates, and the opiate receptors are found even in unicellulars. The opioid system seems to belong to the evolutionary ancient signal systems. The comparative data indicate that the most conservative and ancient function of opioids is control of the adequate level of protective reactions. In the infusorian Stentor the opiate ligands suppress a contractile response to mechanical stimulation, i.e., the protective behavior. In all studies multicellular invertebrates, agonists also suppress protective behavior, whereas antagonists produce opposite effects. This initially signal meaning of opioids might have become a basis for divergent development of their functions in evolution. Already in higher invertebrates, molluscs and arthropods, many functions of opioids, for example, stress-induced analgesia, regulation of feeding and mating behavior, of social aggression, are similar to those in vertebrates. It is suggested that the main events in formation of functions of the endogenous opioid system have occurred in the lower invertebrates that have remained so far the least studied.
When red deer (Cervus elaphus) were hunted by humans with hounds the average distance travelled was at least 19 km. This study of 64 hunted red deer provides the first empirical evidence on their state at the time of death. Blood and muscle samples obtained from hunted deer after death were compared with samples from 50 non-hunted red deer that had been cleanly shot with rifles. The effects on deer of long hunts were (i) depletion of carbohydrate resources for powering muscles, (ii) disruption of muscle tissue, and (iii) elevated secretion of beta-endorphin. High concentrations of cortisol, typically associated with extreme physiological and psychological stress, were found. Damage to red blood cells occurred early in the hunts; possible mechanisms are discussed. Taken together, the evidence suggests that red deer are not well-adapted by their evolutionary or individual history to cope with the level of activity imposed on them when hunted with hounds.
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
More than 200 years ago, Lazzaro Spallanzani (Accademia d’Italia, 1934) wondered how birds — sand martins in his case — found their way back home after they had been displaced inadvertently to unknown territory, but the first to marvel at the amazing homing abilities of insects was Jean Henri Fabre (1879, 1882). He released some megachilid bees and sphecid wasps up to 4 km away from home and was surprised to find that many of them returned to their nesting sites the very same day. Even though he performed a number of experiments including the attachment of tiny magnets to the homing bees, he finally was left with the conclusion that his experimental animals possessed some enigmatic sense of directionality. Nevertheless he started what can be called the first period of research on homing in insects. In this period, which culminated in the discovery of the insect’s celestial compass (Santschi, 1911, 1923; see Wehner, 1990a), most investigators focused on the sensory basis of insect navigation.
Avian pain is likely analogous to pain experienced by most mammals. Approach to pain management for the avian patient involves considering the duration, type, and extent of injury along with physical, environmental, and behavioral management. Invasive, painful procedures should always be accompanied by appropriate analgesia and anesthesia. Although pain management in birds is in its infancy, research and clinical studies demonstrate benefit for use of opioids, steroidal and nonsteroidal anti-inflammatory drugs, as well as other analgesics such as α2-agonists, ketamine, and local anesthetics. Ongoing assessment of pain and analgesic efficacy is extremely important, because the dosage and choice of analgesic may vary widely between species.
In contrast to nociception, the perception of pain, or pain experience, remains a subjective notion applicable to humans, but untestable with animals. Yet, when defined operationally as a physiological response induced in an animal by stimuli painful to humans, and resulting in a protective stimulus avoidance response, pain is amenable to testing with non-human subjects. This paper considers a series of examples showing responses to stimuli that are both painful (nociceptive) and responsible for eliciting natural self-preserving behavior in Invertebrates. Consideration is also given to the evolution and possible mechanism underlying the "pain-system" in Invertebrates.
An alternative collection procedure for pregnant mare urine (PMU) has been developed in Australia, which allows mares to be loose housed either in indoor stables or outdoors in paddocks, rather than in tether stalls as is common practice in Canada and North Dakota. The present study examined the welfare risks to mares of collecting urine using this alternative procedure. The study involved 24 pregnant mares at 3–5 months of gestation. The mares were allocated to two treatments: 12 mares were fitted with the pregnant mare urine collection device and 12 mares acted as controls. All mares were housed in two large paddocks during the day, in two groups of 12. During the night, all mares were housed in six small enclosures in groups of four, while the PMU treatment mares wore the collection device.Mares wearing the PMU collection device showed little or no behavioural change relative to the control mares. While brief bouts of forward lifting of the hind leg in the region of the PMU collection device were observed in some mares on day 1, this disappeared by day 2. Observations on the time budgets of behaviour in weeks 3 and 6–7 indicated similar patterns of behaviour in the two treatments. The only difference in behaviour was in lying behaviour. PMU collection mares spent less (P
The behaviour of the hermit crabClibanarius vittatuswas studied as it investigated shells prior to and during shell exchange interactions. Crabs behaved in a manner predicted by the negotiations model of resource exchange, that is, shells were primarily exchanged between crabs when both crabs benefited in shell fit from the exchange. During initial investigation of shells, crabs in poorly fitting shells selected shells that (1) were similar to the preferred shell size of the investigating crab and (2) that did not fit their current occupant well. In addition, the greater the shell deficit (deviation from that crab's preferred shell size) of the other crab, the more likely it was investigated by a crab in a poorly fitting shell. Considering three factors (initiator's preferred shell size, current shell deficit of the non-initiator and magnitude of gain possible for the non-initiator) explained 86% (multipler=0.93) of the variance in shells rapped by initiating crabs. In those interactions that proceeded to rapping behaviour, the magnitude of gain in shell fit that the non-initiating crab would experience if a shell exchange occurred helped explain which shells were selected for rapping. The relative size of the two crabs was only important in the assessment and decisions process once rapping began, and the number of raps was inversely proportional to the relative size difference of the crabs.
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.
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.
This paper discusses the evidence for pain perception in fish and presents new data on morphine analgesia in fish. Recent anatomical and electrophysiological studies have demonstrated that fish are capable of nociception, the simple detection of a noxious, potentially painful stimulus and the reflex response to this. To prove pain perception, it must be demonstrated that an animal’s behaviour is adversely affected by a potentially painful event and this must not be a reflex response. The present study examined the acute effects of administering a noxious chemical to the lips of rainbow trout (Oncorhynchus mykiss) to assess what changes occurred in behaviour and physiology. There was no difference in swimming activity or use of cover when comparing the noxiously stimulated individuals with the controls. The noxiously treated individuals performed anomalous behaviours where they rocked on either pectoral fin from side to side and they also rubbed their lips into the gravel and against the sides of the tank. Opercular beat rate (gill or ventilation rate) increased almost double fold after the noxious treatment whereas the controls only showed a 30% increase. Administering morphine significantly reduced the pain-related behaviours and opercular beat rate and thus morphine appears to act as an analgesic in the rainbow trout. It is concluded that these pain-related behaviours are not simple reflexes and therefore there is the potential for pain perception in fish.
An understanding of receptors and mechanisms involved in pain and suffering is essential in selecting proper methods of treatment. Detection of pain, knowing types of pain, and understanding reasons why presurgical administration of analgesic drugs (pre-emptive analgesia) is essential to relief of pain and distress. Animals feel pain to the same extent as humans and they have a wide variation in tolerance to pain stimuli as well. Animals may express pain or discomfort in two ways. Excessive activity or relative lethargy are both overt reflections of a painful state. Expressions of pain may be exhibited by moaning, groaning, crying, whimpering, looking at the painful area, licking or biting or simply a decrease in activity. Pain may be categorized as minor, moderate, or severe. Pain may be superficial, somatic (muscle and skin), or visceral or combinations. Moderate and severe pain always require treatment and visceral pain is usually more intense than somatic pain. Opiate receptors are the normal sites of action of several endogenous substances. There are three major types of opioid receptors designated as mu, kappa and sigma. Opioids and opioid antagonists have different affinities for different receptors. Agonist analgesics such as morphine, meperidine, fentanyl, and oxymorphone exert their effects by attaching to the mu receptors. A relatively pure antagonist, naloxone, will displace another compound on these receptors but exert little or no effect. The mixed drugs, agonist–antagonists or partial agonists, may be used as analgesics if no opioid compound has been used, or as antagonists to reverse the effects of an opioid on the mu receptor while at the same time not competing with the effects on the k receptor that is, preserving the analgesia provided by that receptor. Some of the mixed drugs are better agonists wile others are better antagonists. Animals recovering from surgery are often surprised and confused because they hurt and therefore sedation along with analgesia preanesthesia is often desirable and necessary for proper treatment of postsurgical pain. Therefore, giving an analgesic before surgery will be advantageous. The second choice is to give analgesics after surgery, but before recovery from anesthesia.
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.
The ease of autotomy in Hemigrapsus oregonensis was tested by crushing the propodite of each walking leg. Individual curves of percent autotomy in groups of 18–21 animals were drawn for six different sequences of stimulation. Lumped data show peaks in ease of autotomy for the third anatomical leg of each side and for the second leg stimulated regardless of anatomical position. Later autotomies are more severely depressed when the stimulation sequence is from posterior to anterior. Segmental and lateral interaction and the characteristics of individual responses suggest that autotomy of legs in the crab, while depending upon specific structural features of the legs, is less a unisegmental reflex, than an accident occurring during escape.
In an experiment with 10 experimentally naive male hooded rats, it was found that when 1 member of a pair of Ss was insulated from electric footshock, a frequency of aggression was obtained which was far lower than that which has typically been reported in the shock-elicited aggression literature. Also the shocked Ss developed a relatively high frequency of stereotyped responses which served as partially successful avoidance responses. Data support earlier data indicating that avoidance or escape responses to shock will take priority over attack responses to shock. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Crustacean discards experience stress during commercial fishing operations, due to increased exercise while in the trawl and aerial exposure during sorting of the catch. Physiological stress and recovery were assessed following trawling of two ecologically important decapod species, regularly discarded in the Clyde Nephrops fishery. Haemolymph samples taken from trawled swimming crabs, Liocarcinus depurator, and squat lobsters, Munida rugosa, had significantly higher concentrations of ammonia (0.308 and 0.519 mmol l-1), -glucose (0.14 and 0.097 mmol l-1) and -lactate (6.2 and 0.87 mmol l-1) compared with controls, indicating an impairment of ammonia excretion and a switch to anaerobic metabolism. Concurrently, the haemolymph pH of trawled squat lobsters was low (7.47) compared with controls (7.75); however, the reverse trend was found in L. depurator. Initially elevated lactate (7.98 mmol l-1) and glucose (0.73 mmol l-1) concentrations of trawled and emersed (1h) L. depurator were restored, 4h after re-immersion along with pH (7.54). Crabs that had been emersed for 1 h had significantly higher concentrations of glucose (0.2 mmol l-1) and lactate (5.14 mmol l-1), and had more acidic blood (7.64) than L. depurator subject to 1h of exercise, indicating that anoxia was the main cause of physiological stress. Crabs and squat lobsters lost 7% and 9% of their initial body wet weight following 1h of emersion, although blood osmolarities did not change significantly. While all animals survived aerial exposure in our experiments, sorting of the catch on commercial boats takes up to 300min, which could lead to mortality or sub-lethal chronic biochemical changes that could compromise fitness.
We investigated the possibility that invertebrates recognize conspecific individuals by studying dominance relationships in the long-clawed hermit crab, Pagurus longicarpus. We conducted three sets of laboratory experiments to define the time limits for acquiring and maintaining memory of an individual opponent. The results reveal two characteristics that make individual recognition in this species different from standard associative learning tasks. Firstly, crabs do not require training over many repeated trials; rather, they show evidence of recognition after a single 30-min exposure to a stimulus animal. Secondly, memory lasts for up to 4 d of isolation without reinforcement. A third interesting feature of individual recognition in this species is that familiar opponents are recognized even before the formation of a stable hierarchical rank. That is, recognition seems to be relatively independent of repeated wins (rewards) or losses (punishments) in a dominance hierarchy. The experimental protocol allowed us to show that this species is able to classify conspecifics into two ‘heterogeneous subgroups’, i.e. familiar vs. unfamiliar individuals, but not to discriminate one individual of a group from every other conspecific from ‘a unique set of cues defining that individual’. In other words, we demonstrated a ‘binary’– and not a ‘true’– individual recognition. However, 1 d of interactions with different crabs did not erase the memory of a former rival, suggesting that P. longicarpus uses a system of social partner discrimination more refined than previously shown.
To Charles Darwin, it was obvious that animals are sentient, so why should the idea not be now universally accepted? I review the difficulties and issues with animal sentience with a view to answering some of the critics. Sentience is 'the hard problem' and it is important we acknowledge the difficulties and do not claim too much for the evidence we have. Two sorts of evidence are examined: evidence from animal cognition and evidence from animal emotion, including the ways we now have of 'asking' animals what they want, behaviour, brain imaging and parallels with our own emotions. Despite the problems, the study of animal sentience is one of the most important areas of biology. Although conclusive evidence that animals are sentient may elude us, evidence of what they want and how they see the world is increasingly open to us and it is important that it is used. There is a danger that well-meaning people define animal welfare in terms of what they think animals want or what pleases them. But if we take animal sentience seriously, we must ensure that the animal voice is heard. # 2006 Published by Elsevier B.V.
The Clyde Sea Nephrops fishery produces large amounts of invertebrate discards. Of these, as much as 89% are decapod crustaceans, including the
swimming crab Liocarcinus depurator (Linnaeus, 1758), the squat lobster Munida rugosa (Fabricius, 1775) and the hermit crab Pagurus bernhardus (Linnaeus, 1758). The short-term mortality of these species was assessed following trawling and periods of aerial exposure
on deck (16–90 min), and ranged from 2–25%, with Pagurus bernhardus showing the lowest mortality. Two experiments were performed to determine the longer-term survival of trawled decapods compared
to those with experimentally ablated appendages. Deliberately damaged decapods had a significantly lower longer-term survival
(ca. 30%) than controls (72–83%). Survival of trawled Liocarcinus depurator that had been induced to autotomize two appendages was slightly lower (74%) compared with intact creel-caught animals (92%).
Mortality rates stabilised about 10 d after trawling. Our results suggest that post-trawling mortality of discarded decapod
crustaceans has been underestimated in the past, owing to inadequate monitoring periods.
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.
Can suffering in non-human animals be studied scientifically? Apart from verbal reports of subjective feelings, which are uniquely human, I argue that it is possible to study the negative emotions we refer to as suffering by the same methods we use in ourselves. In particular, by asking animals what they find positively and negatively reinforcing (what they want and do not want), we can define positive and negative emotional states. Such emotional states may or may not be accompanied by subjective feelings but fortunately it is not necessary to solve the problem of consciousness to construct a scientific study of suffering and welfare. Improvements in animal welfare can be based on the answers to two questions: Q1: Will it improve animal health? and Q2: Will it give the animals something they want? This apparently simple formulation has the advantage of capturing what most people mean by ‘improving welfare’ and so halting a potentially dangerous split between scientific and non-scientific definitions of welfare. It can also be used to validate other controversial approaches to welfare such as naturalness, stereotypies, physiological and biochemical measures. Health and what animals want are thus not just two of many measures of welfare. They provide the definition of welfare against which others can be validated. They also tell us what research we have to do and how we can judge whether welfare of animals has been genuinely improved. What is important, however, is for this research to be done in situ so that it is directly applicable to the real world of farming, the sea or an animal’s wild habitat. It is here that ethology can make major contributions.
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.
The mantis shrimpSquilla mantis responds to an electrical shock with a quick and violent flexure of its body (Fig. 1 and 2). The reaction time of this defensive response was measured for each experimental shrimp and the minimal current that elicited a reaction time equal to or lesser than 0.22 s was considered as its intensity threshold (Fig. 3). Different doses of morphine-HCl were injected and results showed that this drug produces a dose-related analgesia by increasing the intensity threshold. A concentration of morphine equal to 30.0 μg/mm of animal length (about 91.0 μg/g) causes a 50% inhibition in the sensitivity to the electrical stimulus, but the effect is fully blocked by naloxone (Table 2).
The present study represents the first behavioral analysis of opiate effects in invertebrates. However, the effective dose reported in this experiment is far greater than that used with vertebrates. Some speculative arguments are mentioned in order to account for a such large difference.
1.
Kinesthetic reorientation to the burrow as already assumed to be present in Uca tangeri (R. Altevogt u. H. O. v. Hagen, 1964) was shown in Uca rapax by field experiments in Trinidad (West Indies).
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The kinesthetic orienting mechanism is found to operate with striking precision within a certain area around the burrow and is able to control distance as well as direction (bi-coordinate or vector orientation).
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When missing the burrow Uca after a motionless interval starts zigzagging transversely to the previous direction. These locomotions are interpreted as searching movements.
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According to a few supplementary experiments, U. leptodactyla can reorient kinesthetically as well, and the related ghost crab, Ocypode quadrata, is at least capable of kinesthetic distance control.
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Some observations (especially on patterns of feeding pellets) indicate a possible ability of kinesthetic detour integration in Uca.
6.
In the discussion an attempt is made to classify some examples of kinesthetic orientation known from literature. Three types are given: kinesthetically controlled stereotyped locomotion, kinesthetic reorientation, kinesthetic distance indication.
This article reviews three studies of agonistic interactions in pairs of swimming crabs (Liocarcinus depurator and Necora puber) in which behavioural and physiological approaches were combined. In both species most fights were won by the larger crab. Smaller crabs were able to win fights when the size differential was small, in which case encounters tended to be long and fierce. In N. puber both the larger and the smaller crab were more likely to win fights that they initiated, suggesting that motivational differences (perhaps related to resource value) as well as relative size determine what crabs do during a fight. When fighting during the breeding season in water in which receptive females had been housed, small crabs were as likely as large ones to win fights, by persisting much longer than they did in the absence of such stimuli. In L. depurator an absolute size effect was found, with larger crabs fighting for longer regardless of relative size. This suggested that costs fall more heavily on smaller crabs, and prompted a study of the respiratory costs of fighting. Using scaphognathite beat as an index of oxygen consumption, aerobic respiration was found to be greatly elevated during fights and to remain high for some time after the fight had ended. Long and/or intense fights involved a greater increase in respiration rate. Winners and losers had similar average respiration rates during fights but, in losers, long fights were associated with significantly elevated respiration rates during the recovery period. Analysis of tissue metabolites gave little evidence of anaerobic respiration during fights, although some local mobilisation of glucose in the walking legs was observed. No significant effects of participation in a fight were found on initiation or outcome of a second fight staged immediately afterwards. Sequential associations between agonistic acts indicate a short-term escalatory process that was more marked in winners than losers, which tended to de-escalate especially during high intensity phases. The insights gained by combining behavioural and physiological techniques are discussed.
The supratidal shore crab Leptograpsus variegatus makes use of aquatic as well as terrestrial habitats. The respiratory responses of this species to 12 h immersion in 100% seawater and re-emersion were investigated. The major perturbation was in haemolymph CO2, the PCO2 declining to 2.2 torr after 2 h in water compared to >4 torr in air-breathing crabs. Similarly, CCO2 decreased from 12.8 typical of air breathing to 5.0 mmol · l−1, more typical of water breathing species. This internal hypocapnia promoted an alkalosis which was immediately compensated by a metabolic acidosis that was not a product of anaerobiosis since l-lactate in the haemolymph remained low (0.14 mmol · l−1). When re-emersed, haemolymph CO2 did not increase to pre-immersion values but, instead, evinced a smaller elevation after 3 h access to air. Control Leptograpsus that could choose between water and air showed intermediate but more variable haemolymph CO2 values, suggesting that the animals ‘shuttle’ between air and water, behaviourally influencing internal CO2 levels.
This review on homing in decapods, which has been shown by Herrnkind (1983) and Wehner (1992), indicates how scarce our knowledge is, not only on the physiological mechanisms involved in such behaviour but also on the reality and extent of the behaviour itself.The case studies cited (first part) show that among decapods (only “reptants” are considered here), some species seem to wander at random, some can keep within a more or less well defined home range with no particular “home” while yet others are known to relocate periodically a definite restricted goal. Although burrows and shelters are the primary homing goals, cases of relocation of food resources and mates have also been reported. Some decapods occupy a single shelter, while others tend to visit, on a more or less regular basis, a system of shelters. The second part of this review deals with the mechanisms involved in decapod homing. Apart from idiothetic mechanisms, visual cues certainly play the most important role among terrestrial or semi-terrestrial species. Chemical cues may play a role in benthonic species, although direct evidence for this is still lacking. In certain cases a cognitive map relying on a system of orienting cues can be inferred.
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.
Energetic costs of fighting, such as high lactate or low glucose, have been shown in a range of species to correlate with the decisions made by each opponent, particularly the decision by one opponent, the ‘loser’, to end the fight by ‘giving up’. Studies based on complete fights of differing duration, however, do not provide information on the changes in the physiological correlates of fighting that may take place during the course of the encounter, or how these changes may influence the capability and decisions of the contestants. We interrupted fights between hermit crabs, Pagurus bernhardus, at specific points, and related energy status to the preceding activities. Costs rose quickly with a rapid accumulation of lactic acid in attackers and declining muscular glycogen in defenders. Changes in physiological status appeared much earlier than the changes in behaviour that they may have caused. Furthermore, some physiological changes might have been an effect, rather than the cause, of fight decisions.
Animal fights are typically preceded by displays and there is debate whether these are always honest. We investigated the prefight period in hermit crabs, Pagurus bernhardus, during which up to four types of display plus other activities that might provide information are performed. We determined how each display influences or predicts various fight decisions, and related these displays to the motivational state of the attacker, as determined by a startle response, and of the motivational state of the defender, as determined by the duration for which it resisted eviction from its shell. Two displays appeared to have consistent but different effects. Cheliped presentation, where the claws were held in a stationary position, often by both crabs but for longer by the larger, seemed to be honest, and allowed for mutual size assessment. This display enhanced the motivation and the success of the larger crab. In contrast, cheliped extension, involving the rapid thrust of the open chelae towards the opponent, did not seem to allow for mutual size assessment and may contain an element of bluff. It was performed more by the smaller crab and enhanced its success. The complexity of displays in this species appears to allow for both honesty and manipulation.
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.
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.
The process by which animals gather the information required to make a decision on whether or not to accept a resource was examined. A motivational model was developed to predict how information changes levels of causal factors and the model was tested by experiments on hermit crabs investigating shells. A prediction of the model is that, when there is a high utility in accepting the resource, each stage of the assessment procedure will be rapid, whereas if the utility is low the assessment will be prolonged. If the resource is not available for some reason, for example if a shell has the aperture blocked, the animal will persevere for longer if the initial stages of assessment indicated a high-quality resource than if it had indicated a low-quality resource. These and other predictions of the model were upheld in experiments in which the information available to hermit crabs at each stage of assessment was varied.
Neuronal biosensors based on the use of crayfish Procambarus clarkii walking legs are reported for the first time and possible analytical applications are explored. The neuronal biosensor is shown to respond selectively to the antitubercular drug and potent food marker, pyrazinamide. The sensor is characterized with respect to selectivity, dose-response relationship, reproducibility and operating lifetime. The detection of local anesthetics is accomplished by monitoring the decrease in pyrazinamide-induced nerve firing in the crayfish walking leg. This decrease is a result of the local anesthetic block of the axonal sodium channels in the nerves. Applicability of this novel procedure to analytical measurements is demonstrated by the construction of dose-response curves for several local anesthetics. Problems associated with the current sensor configuration are presented and future research directions that may improve the neuronal-based biosensor are discussed.