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Can insects feel pain? A review of the neural and behavioural evidence
Abstract
The entomology literature has historically suggested insects cannot feel pain, leading to their exclusion from ethical debates and animal welfare legislation. However, there may be more neural and cognitive/behavioural evidence for pain in insects than previously considered. We use Birch et al. 's (2021) eight criteria for sentience to critically evaluate the evidence for pain in insects. We assess six orders (Blattodea, Coleoptera, Diptera, Hymenoptera, Lepidoptera, and Orthoptera) in at least two life stages (adult and first instar juveniles, as well as other instars where relevant data are found). Other insect orders have not received enough research effort to be evaluated. According to the Birch et al. framework, adult Diptera (flies and mosquitoes) and Blattodea (cockroaches and termites) satisfy six criteria, constituting strong evidence for pain. Adults of the remaining orders (except Coleoptera, beetles) and some juveniles (Blattodea and Diptera, as well as last instar Lepidoptera [butterflies and moths]) satisfy 3–4 criteria, or “substantial evidence for pain”. We found no good evidence that any insects failed a criterion. However, there were significant evidence gaps, particularly for juveniles, highlighting the importance of more research on insect pain. We conclude by considering the ethical implications of our findings where insects are managed in wild, farmed, and research contexts.
... The IAFF industry is expected to grow substantially in the coming decades (de Jong and Nikolik, 2021), and thus represents one of the largest ever undertakings of industrial livestock rearing in terms of the number of individual animals. Despite some uncertainty about insect sentience (Adamo, 2019(Adamo, , 2016, recent literature suggests insect sentience is plausible (Gibbons et al., 2022), and therefore many academics, consumers, producers, and professional societies have expressed an interest in the welfare of insects Bear, 2021Bear, , 2019de Goede et al., 2013;Delvendahl et al., 2022;Erens et al., 2012;Gjerris et al., 2016;IPIFF, 2019;Klobučar and Fisher, 2023;Voulgari-Kokota et al., 2023). ...
... incomplete metamorphosis), while all insects investigated to date are holometabolous (i.e. complete metamorphosis); these different developmental strategies may bear significantly on the question of animal welfare at the juvenile life stage due to critical differences in the developmental timing of discrete, sensory integrative brain regions and, possibly, connections between them (Barrett and Fischer, 2023;Gibbons et al., 2022;Fischer and Sandall, 2023). ...
... sentience -have welfare states (Bentham, 1789;Broom, 2019;Dawkins, 1990;Singer, 2002;Webster, 1994). The empirical evidence does not provide a clear answer to the question of insect sentience (Adamo, 2016;Birch, 2022;Klein and Barron, 2016;Lambert et al., 2021), although a recent review found strong evidence for pain in several insect taxa despite current research gaps (Gibbons et al., 2022). One approach, including for insect mini-livestock (Röcklinsberg et al., 2017;van Huis, 2021), to managing uncertainty around animal sentience is the "precautionary principle", which suggests sensible precautionary measures should be taken to protect the welfare of animals when there is evidence that they may be sentient (Birch, 2017;Knutsson and Munthe, 2017). ...
Orthoptera, such as crickets, is currently the most reared group of hemimetabolous insects in the insects as food and feed industry, with over 370 billion individuals slaughtered and/or sold live annually. The most-farmed cricket species is Acheta domesticus , however there is growing interest in farming at least two additional species, Gryllus assimilis and Gryllodes sigillatus . Crickets are largely being explored for use as human protein, and exotic animal or pet feed – as well as, to a lesser extent, livestock and fish feed. Insect welfare is of growing interest to consumers who are considering incorporating insect protein into their diets, as well as to many producers. However, no studies have considered the welfare concerns of farmed crickets under current industry conditions. Using an established model for assessing farmed insect welfare, we assess potential welfare concerns for the three most-farmed cricket species, including: interspecific interactions (including parasites and pathogens), temperature and humidity, light cycles, electrical shocks, atmospheric gas levels, nutrition and hydration, environmental pollutants, injury and crowding, density, handling-associated stress, genetics and selection, enrichments, transport-related challenges, and stunning, anesthesia, and slaughter/depopulation methods. From our assessment of these factors, we make recommendations for improving cricket welfare now and as the industry continues to grow; in addition, we identify research directions that will improve our understanding of cricket welfare. We conclude by broadly discussing the importance of addressing the welfare challenges presented by the insects as food and feed industry for the animals and for the growth and health of the industry itself.
... However, a recent review of neurobiological and behavioural research on insects indicates sentience is plausible (Gibbons et al. 2022), especially in some orders with farmed insects (e.g. black soldier flies [Hermetia illucens], BSF, in the order Diptera). ...
... black soldier flies [Hermetia illucens], BSF, in the order Diptera). Importantly, developmental stage may impact the likelihood of sentience in an insect species, especially in the holometabolous insects that undergo a complete metamorphosis (for discussions, see Gibbons et al. 2022;Fischer & Sandall 2023). For instance, Gibbons et al. (2022) found that adult dipterans meet six of eight criteria for sentience according to the Birch et al. (2021) invertebrate sentience framework while slaughter-age larval dipterans met only four of eight; the remaining two, or four, criteria, respectively, had not yet been assessed for that order at that life stage. ...
... Importantly, developmental stage may impact the likelihood of sentience in an insect species, especially in the holometabolous insects that undergo a complete metamorphosis (for discussions, see Gibbons et al. 2022;Fischer & Sandall 2023). For instance, Gibbons et al. (2022) found that adult dipterans meet six of eight criteria for sentience according to the Birch et al. (2021) invertebrate sentience framework while slaughter-age larval dipterans met only four of eight; the remaining two, or four, criteria, respectively, had not yet been assessed for that order at that life stage. While the framework rated adult dipterans as having "strong evidence for sentience", last instar larval dipterans still fulfilled enough criteria for there to be "substantial evidence for sentience" at this life stage. ...
At least 200 billion black soldier fly ( Hermetia illucens ) larvae (BSFL) are reared each year as food and feed, and the insect farming industry is projected to grow rapidly. Despite interest by consumers, producers, and legislators, no empirical evidence exists to guide producers in practicing humane – or instantaneous – slaughter for these novel mini-livestock. BSFL may be slaughtered via freezing, boiling, grinding, or other methods; however standard operating procedures (SOPs) and equipment design may affect the likelihood of instantaneous death using these methods. We tested how larval body size and particle size plate hole diameter affect the likelihood of instantaneous death for black soldier fly larvae that are slaughtered using a standard meat grinder. Larval body size did not affect the likelihood of instantaneous death for larvae that are 106–175 mg in mass. However, particle size plate hole diameter had a significant effect on the likelihood of instantaneous death, with only 54% of larvae experiencing an instant death when using the largest particle size plate (12-mm hole diameter) compared to 84% using the smallest particle size plate (2.55 mm). However, a higher percentage of instantaneous death (up to 99%) could be achieved by reducing the proportion of larvae that become stuck in the machine. We conclude by outlining specific recommendations to support producers in achieving a 99% instantaneous death rate through specific SOPs to be used with similarly designed machines. We also develop a protocol for producers that wish to test their own grinding SOPs.
... To date, most arguments put forth for considering insect welfare are ethical ones, based on the emerging evidence that at least some insect species may be sentient and that the precautionary principle should be adopted in cases of uncertainty (e.g. Gibbons et al., 2022a;van Huis, 2021). This principle suggests that the IAFF industry treat insects as though they are sentient to avoid causing potentially significant harm to a very large number of individuals (with stronger and weaker versions of what this entails; Birch, 2017;Knutsson and Munthe, 2017). ...
... Insects of several orders meet many of the criteria relevant to sentience (criteria developed in Crump et al., 2022, adapted from Smith andBoyd, 1991; over 300 studies reviewed for insects in Gibbons et al., 2022a). Insects have sensory cells called nociceptors that respond to a range of noxious stimuli (Caron et al., 2020;Grueber et al., 2001;Khoung et al., 2019;Tracey et al., 2003). ...
... Insects' behavioral responses to noxious stimuli are modulated by endogenous and exogenous chemicals that affect the nervous system in ways that are consistent with the hypothesis that negative affective states are being attenuated (Araujo et al., 2021;Hibicke and Nichols, 2022;Jang et al., 2023;Manev and Dimitrijevic, 2004; but see Groening et al., 2017, while noting that insects have no opioid receptors, Mirabeau and Joly, 2013). The most evidence for insect pain has been found in the adult Blattodea (cockroaches, termites) and Diptera (flies, mosquitoes; Gibbons et al., 2022a), which both include farmed species used as livestock or pet feed. Some insects are capable of self-protective behaviors (Hentschel and Penzlin, 1982;Jang et al., 2023;Walters et al., 2001; but see Eisemann et al., 1984, with comments by Gibbons andSarlak, 2020) and motivational tradeoffs in response to harmful and rewarding stimuli (Gibbons et al., 2022b;Kaun et al., 2011;Manev and Dimitrijevic, 2004). ...
The insects as food and feed (IAFF) industry represents one of the largest undertakings of industrial livestock rearing in human history, with at least a trillion animals reared each year and massive growth potential. As other livestock industries have grown, animal welfare science has become an essential field for maintaining socially responsible, ethical, and sustainable industry practice. Like traditional livestock industries, the IAFF industry could also benefit – ethically, socially, and economically – from a field of welfare science. Here, we present three economic reasons for considering animal welfare in intensive production systems: (1) improving production outcomes, (2) maintaining social license to operate, and (3) differentiating products. In each case, we provide examples from established livestock industries that highlight how the field of animal welfare science can benefit producers. Further, we provide examples of how the IAFF industry would benefit from the support of a dedicated field of welfare science. We end by calling attention to key partnerships between entomologists, welfare scientists, and producers that could advance the common goals of these stakeholder groups, as well as animal welfare in insect agriculture.
... Nevertheless, extending welfare legislation to more and more animal groups, often following intense lobbying by activist non-government organizations (NGOs) is problematic, as the evidence used to support this move includes advocacy-based reviews (not meta-analyses) which provide contentious interpretations of a limited body of scientific evidence that has significant technical and interpretational flaws (reviewed in Rose et al. 2014;Key 2015;Browman et al. 2019;Diggles 2019;Mason and Lavery 2022;Hart 2023). In fact, the reviews of Birch et al. (2021) and Crump et al. (2022) are being interpreted so broadly and so uncritically in certain policy-making circles that legislators risk following a path ending with all animals including insects and even plankton, eventually being included in welfare legislation (Gibbons et al. 2022;Crump et al. 2022Crump et al. , 2023. The ramifications of these developments on food production, and on how humans interact with animals, would be profound and far reaching (Browman et al. 2019). ...
... A broad definition of sentience is being extended from terrestrial vertebrates into not only fish, crustaceans, molluscs, and other invertebrates including insects (Crump et al. , 2023Gibbons et al. 2022), but also plants (Calvo et al. 2017;Chamovitz 2018;Baluška and Mancuso 2021) and cell cultures (Niikawa et al. 2022). Most of this discussion is philosophical in nature, since measuring "pleasure" and "pain" in these groups in any scientifically valid context remains challenging and riddled with inconsistencies, technical problems (e.g., Bennett et al. 2009;Borrelli et al. 2020) and subjective anthropomorphic assumptions (e.g., for fishes see Rose et al. 2014;Mason and Lavery 2022;Hart 2023; and for plants see Brown and Key 2021). ...
... The argument that bees are sentient is illustrative of some of the problems of adopting this approach. If the potentially unfalsifiable hypothesis that bees are sentient is accepted (Gibbons et al. 2022;Crump et al. 2023), ignoring the fact that their behaviors can be replicated by robots (Adamo 2019), it follows that all insects are potentially sentient and should therefore be theoretically protected under welfare regulation. This situation would lead to widespread noncompliance with welfare legislation when farmers need to protect their crops from predatory insects. ...
Psychology and vision science, university of leicester, leicester, uK; j school of veterinary science, Murdoch university, Perth, wA, Australia; k Department of ichthyology, Faculty of Biology, lomonosov Moscow state university, Moscow, Russia; l school of Biomedical sciences, university of queensland, Australia; m Pepperell Research and consulting, noosaville, qlD, Australia; n Kansas Biological survey, and the Biodiversity institute, the university of Kansas, lawrence, Ks, usA; o emeritus (Retired) Department of Zoology and Physiology, university of wyoming laramie, wY, usA; p Britannia heights, nelson, new Zealand; q Biomed sci, Atlantic veterinary college, university of Pei, charlottetown, canada; r the college of william & Mary, virginia institute of Marine science, Gloucester Point, virginia, usA; s emeritus (Retired) tropical Aquaculture laboratory, university of Florida, Gainesville, usA ABSTRACT The welfare of fishes and aquatic invertebrates is important, and several jurisdictions have included these taxa under welfare regulation in recent years. Regulation of welfare requires use of scientifically validated welfare criteria. This is why applying Mertonian skepticism toward claims for sentience and pain in fishes and aquatic invertebrates is scientifically sound and prudent, particularly when those claims are used to justify legislation regulating the welfare of these taxa. Enacting welfare legislation for these taxa without strong scientific evidence is a societal and political choice that risks creating scientific and interpretational problems as well as major policy challenges, including the potential to generate significant unintended consequences. In contrast, a more rigorous science-based approach to the welfare of aquatic organisms that is based on verified, validated and measurable endpoints is more likely to result in "win-win" scenarios that minimize the risk of unintended negative impacts for all stakeholders, including fish and aquatic invertebrates. The authors identify as supporters of animal welfare, and emphasize that this issue is not about choosing between welfare and no welfare for fish and aquatic invertebrates, but rather to ensure that important decisions about their welfare are based on scientifically robust evidence. These ten reasons are delivered in the spirit of organized skepticism to orient legislators, decision makers and the scientific community, and alert them to the need to maintain a high scientific evidential bar for any operational welfare indicators used for aquatic animals, particularly those mandated by legislation. Moving forward, maintaining the highest scientific standards is vitally important, in order to protect not only aquatic animal welfare, but also global food security and the welfare of humans.
... The approach used here will not employ a formal scoring system like that of Crump et al. [9] and Gibbons et al. [24]. That is because there is little agreement about the weighting of scores from different criteria [17,18] or about the inclusion/exclusion of criteria [16]. ...
... Numerous studies demonstrated avoidance learning in insects and these are reviewed in detail by Gibbons et al. [24] and Pitman et al. [45]. For example, fruit flies (Drosophila melanogaster) avoided an odour that had been associated with electric shocks, even after just one trial, and they showed retention of the learning after 24 h [46]. ...
... For example, fruit flies (Drosophila melanogaster) avoided an odour that had been associated with electric shocks, even after just one trial, and they showed retention of the learning after 24 h [46]. Honeybees (Apis mellifera) associated electric shock or heat with preceding cues and similar classical conditioning has been shown in several other insects [24]. Operant conditioning to avoid noxious stimuli has also been shown, for example, in cockroaches (Periplaneta americana) and honeybees that learned to avoid locations in which they received electric shocks [47,48]. ...
Pain in response to tissue damage functions to change behaviour so that further damage is minimised whereas healing and survival are promoted. This paper focuses on the behavioural criteria that match the function to ask if pain is likely in the main taxa of arthropods. There is evidence consistent with the idea of pain in crustaceans, insects and, to a lesser extent, spiders. There is little evidence of pain in millipedes, centipedes, scorpions, and horseshoe crabs but there have been few investigations of these groups. Alternative approaches in the study of pain are explored and it is suggested that studies on traumatic mating, agonistic interactions, and defensive venoms might provide clues about pain. The evolution of high cognitive ability, sensory systems, and flexible decision-making is discussed as well as how these might influence the evolution of pain-like states.
... Some scientists have expressed skepticism about insect pain, pointing to their small nervous systems and apparently reflexive nocifensive behaviors [1]. Nonetheless, recent work has undermined these assertions (e.g., [2,3]). ...
... In a comprehensive review, we evaluated over 300 studies to understand the current state of evidence relevant to pain in 6 major insect groups [3]. We adopted a contemporary framework for assessing evidence relevant to pain, which has previously guided welfare policy [4]. ...
... In one study, injured honeybees did not selfadminister an analgesic (morphine) more than uninjured bees [5]. This is unsurprising since insects lack opioid receptors to detect morphine [3]. However, using opioid receptors as evidence relevant to pain is too vertebrate centric. ...
Recent evidence suggests that at least some insect species might plausibly feel pain. These findings should prompt researchers to think about the welfare implications of insect experiments.
... This pertains to how the state is experienced from the first-person perspective respectively "what it's like" (Nagel, 1974) to be in such a state. Comparative cognition researchers often refer to the same kind of property (e.g., Gibbons et al., 2022;Mason & Lavery, 2022;Nieder et al., 2020;Panksepp, 2010). ...
... It is obvious that evaluative consciousness is a constituent of wellbeing. Since (as in Birch et al., 2020) evaluative richness refers to the feeling of valence, not to any kind of sophisticated cognitive evaluation, it is plausible that many animals, perhaps even invertebrates, have evaluative experiences (Crook, 2021;Crump et al., 2022;Galpayage Dona et al., 2022;Gibbons et al., 2022). Things can be good or bad for animals because they feel good or bad to them. ...
Whether animals fare well or not is of ethical significance. For this reason, their capacity for wellbeing, i.e., how good or bad the lives of animals can go, is of ethical significance as well. I assume that the wellbeing of most animals is mainly determined by their phenomenally conscious experiences. If consciousness differences between species determine wellbeing differences, then the kinds of conscious experience species are capable of may entail that some species systematically (can) have higher or lower wellbeing than others. Then, I argue that not all phenomenally conscious states contribute to wellbeing equally. I discuss which features of consciousness are constituents of wellbeing and which can, for ethical purposes, be ignored. In addition, I scrutinize how much different features of experience contribute to wellbeing and how their presence can be detected empirically. This way, this paper exemplifies a novel consciousness-centered approach for the empirical investigation of animal wellbeing. The strengths and weaknesses of this approach are analyzed. While subsequent research is needed to refine the framework, I already note some preliminary implications for animal ethics.
... Sentience refers to the capacity for individual subjective experience, such that there is something that it is like to be that individual; sometimes also called phenomenal consciousness (Browning & Birch, 2022). With the ever-growing recognition of the sentience of species even very evolutionarily distant from us (e.g., Birch et al., 2021b;Crump et al., 2022;Gibbons et al., 2022), it is clear that brain organoids -even those grown from non-human tissue -have the potential for sentience. Sentience is now a common basis for legislative and ethical protection (Browning & Veit, 2022) and is also commonly considered a basis for being a welfare subject. ...
... Sentience refers to the capacity for individual subjective experience, such that there is something that it is like to be that individual; sometimes also called phenomenal consciousness (Browning & Birch, 2022). With the ever-growing recognition of the sentience of species even very evolutionarily distant from us (e.g., Birch et al., 2021b;Crump et al., 2022;Gibbons et al., 2022), it is clear that brain organoids -even those grown from non-human tissue -have the potential for sentience. Sentience is now a common basis for legislative and ethical protection (Browning & Veit, 2022) and is also commonly considered a basis for being a welfare subject. ...
One of the most urgent challenges arising in bioethics has been the ethical assessment of the use of brain organoids, largely because of the possibility of sentience and the potential that if they can feel, then they might suffer. But while there is a growing literature on the possibility of sentience in brain organoids and why we should take a precautionary approach towards them, there is very little guidance on what it would mean to protect their welfare. In this paper, we address this omission by exploring the question of what the welfare of an organoid might be like, and how we could scientifically assess this question. As we will show, these are difficult questions to answer, given the current lack of empirical data on many of the important features of brain organoids, but we will provide some principled empirically-informed speculation on possible answers, as well as suggestions for future research directions.
... For discussion of insect consciousness, see(Klein and Barron 2016;Gibbons et al., 2022); for discussion of the cognitive status of eusocial insect colonies, see(Huebner 2014), and for discussion of their potential consciousness see(Friedman and Søvik 2021).12 For discussion see, esp.(Carls-Diamante, 2017.Content courtesy of Springer Nature, terms of use apply. ...
It may soon be possible for neurotechnology to connect two subjects' brains such that they share a single token mental state, such as a feeling of pleasure or displeasure. How will our moral frameworks have to adapt to accommodate this prospect? And if this sort of mental-state-sharing might already obtain in some cases, how should this possibility impact our moral thinking? This question turns out to be extremely challenging, because different examples generate different intuitions: If two subjects share very few mental states, then it seems that we should count the value of those states twice, but if they share very many mental states, then it seems that we should count the value of those statesonce. We suggest that these conflicting intuitions can be reconciled if the mental states that matter for welfare have a holistic character, in a way that is independently plausible. We close by drawing tentative conclusions about how we ought to think about the moral significance of shared mental states.
... Going beyond the behavioral sciences and philosophy, our results support recent efforts to better understand the sentience of various entities, such as insects (Gibbons et al., 2022), plants (Calvo & Segundo-Ortin, 2023), and AI systems (Butlin et al.,202 C.E.). There may never be a clearly defined, quantitative way of determining the moral status of different entities in a society. ...
Whose well-being and interests matter from a moral perspective? This question is at the center of many polarizing debates, for example, on the ethicality of abortion or meat consumption. People’s attributions of moral standing are guided by which mental capacities an entity is perceived to have. Specifically, perceived sentience (e.g., the capacity to feel pleasure and pain) is thought to be the primary determinant, rather than perceived agency (e.g., the capacity for intelligence) or other capacities. This has been described as a fundamental feature of human moral cognition, but evidence in favor of it is mixed and prior studies overwhelmingly relied on North American and European samples. Here, we examined the link between perceived mind and moral standing across six culturally diverse countries: Brazil, Nigeria, Italy, Saudi Arabia, India, and the Philippines (N = 1,255). In every country, entities’ moral standing was most strongly related to their perceived sentience.
... Besides the environmental, economic, and nutritional advantages, another positive aspect of breeding and consuming insects has been highlighted in terms of ethical implication. In fact, it is likely that they are not sentient, (Pali-Schöll et al., 2019), even if this issue is highly controversial and debated, with recent publications in contradiction (Adamo, 2019;Gibbons et al., 2022). ...
... This would make mantids an interesting species for studies of insect pain perception, a field of growing research interest given the development of large-scale insect farming and associated welfare concerns (e.g. van Huis 2021; Gibbons et al. 2022;Barrett and Adcock 2023). ...
Praying mantids (Mantodea: Mantidae) are iconic insects that have captivated biologists for decades, especially the species with cannibalistic copulatory behavior. This behavior has been cited as evidence that insects lack nociceptive capacities and cannot feel pain; however, this behaviorally driven hypothesis has never been rigorously tested at the genetic or functional level. To enable future studies of nociceptive capabilities in mantids, we sequenced and assembled a draft genome of the Chinese praying mantis (Tenodera sinensis) and identified multiple classes of nociceptive ion channels by comparison to orthologous gene families in Arthropoda. Our assembly - produced using PacBio HiFi reads - is fragmented (Total size = 3.03Gb; N50 = 1.8Mb; 4966 contigs), but is highly complete with respect to gene content (BUSCO complete = 98.7% [odb10_insecta]). The size of our assembly is substantially larger than that of most other insects, but is consistent with the size of other mantid genomes. We found that most families of nociceptive ion channels are present in the T. sinensis genome; that they are most closely related to those found in the damp-wood termite (Zootermopsis nevadensis); and that some families have expanded in T. sinensis while others have contracted relative to nearby lineages. Our findings suggest that mantids are likely to possess nociceptive capabilities and provide a foundation for future experimentation regarding ion channel functions and their consequences for insect behavior.
... Insofar as we too care about harm to animals, our outreach might put more emphasis on killing humanely. If insects are individuals-ones that may even have the capacity to feel pain (Gibbons et al. 2022)-then it makes sense for people to have more reservations about killing them. We thus have reason to encourage people to kill them in ways that minimize the possibility of suffering-both for the insects' sake and, in response to this father's concern, for the sake of cultivating certain attitudes toward wildlife. ...
... Ultimately, our data add to a growing repository of literature that focuses on the welfare of insects being mass-reared for human food and/or animal feed (Gibbons et al. 2022). Our specific focus on how US consumers perceive commercial insect production for the livestock industry, with an emphasis on their perceptions of insect pain and ethical concerns, is unique in highlighting some potential vectors of resistance to the development of the emerging insect rearing industry in the US In particular, our data indicate that a surprising number of consumers believe that insects can feel pain, that the percentage is even higher among those who oppose insect farming, that more knowledge about the industry is correlated with more opposition, and that the young are most concerned. ...
Insects have potential to be integrated into livestock production systems as feed. However, to be viable as feed, insects must be mass-reared in a ‘mini-livestock’ system. As these mass-rearing systems are relatively new, industry standards and welfare regulations are not yet in place, leaving insect welfare-related questions open. Given the importance of consumer attitudes to the social legitimacy of insect production, an analysis of consumers’ ethical perceptions of producing insects as livestock feed is warranted. The objectives of this study were to: (1) determine if US consumers support or oppose using insects as livestock feed, (2) determine if perceptions regarding insect welfare or ethics are reasons for opposition, and (3) identify US consumers’ perceived risks and benefits of using insects as livestock feed. We developed a quantitative electronic questionnaire-based survey and established reliability and validity prior to distribution. Distribution was achieved through convenience sampling to adult US consumers (n = 361). When asked if insects should be used as livestock feed, 34% of respondents were supportive, 52% were neutral, and 15% were opposed. Of those who were opposed (n = 53), 58% cited ethical concerns as their reason for opposition. Of respondents who were supportive or neutral towards using insects as livestock feed (n = 308), 29% reported livestock welfare and 26% reported insect welfare as perceived risks. Perceived benefits emphasised environmental sustainability. From our entire sample, 74% of respondents thought insects could feel pain, 23% did not know, and 4% did not think insects could feel pain. Gender, age, household income, education level, and previous knowledge were significant determinants ( ) of whether or not respondents thought insects could feel pain. Our data highlight potential areas of opposition to developing the insect rearing industry in the US and suggests that producers have reason to establish practices that are perceived as creating high-welfare conditions for their insects.
... insects, crustaceans, cephalopods (Schmidt-Rhaesa, Harzsch & Purschke, 2016)]. There is now evidence that this high degree of centralisation is likely related to sentience in several invertebrate species (Birch et al., 2021;Lambert, Elwin & D'Cruze, 2021;Gibbons et al., 2022). In insects, the central nervous system appears to be able to support some functions analogous to those of the mammalian brain (Klein & Barron, 2016). ...
Affective states, such as emotions, are presumably widespread across the animal kingdom because of the adaptive advantages they are supposed to confer. However, the study of the affective states of animals has thus far been largely restricted to enhancing the welfare of animals managed by humans in non-natural contexts. Given the diversity of wild animals and the variable conditions they can experience, extending studies on animal affective states to the natural conditions that most animals experience will allow us to broaden and deepen our general understanding of animal welfare. Yet, this same diversity makes examining animal welfare in the wild highly challenging. There is therefore a need for unifying theoretical frameworks and methodological approaches that can guide researchers keen to engage in this promising research area. The aim of this article is to help advance this important research area by highlighting the central relationship between physiology and animal welfare and rectify its apparent oversight, as revealed by the current scientific literature on wild animals. Moreover, this article emphasises the advantages of including physiological markers to assess animal welfare in the wild (e.g. objectivity, comparability, condition range, temporality), as well as their concomitant limitations (e.g. only access to peripheral physiological markers with complex relationships with affective states). Best-practice recommendations (e.g. replication and multifactorial approaches) are also provided to allow physiological markers to be used most effectively and appropriately when assessing the welfare of animals in their natural habitat. This review seeks to provide the foundation for a new and distinct research area with a vast theoretical and applied potential: wild animal welfare physiology.
... There are reasons to take this idea seriously. SeeGibbons et al. (2022) for a recent review of the evidence. 7 There are various options here. ...
Martha Nussbaum’s Justice for Animals calls upon humanity to secure for all sentient beings the central capabilities they need to flourish. This essay review critically examines the ethical and scientific foundations of Nussbaum’s position. On the ethical side, we explore the tension between a robust defence of animal rights and political liberalism, which requires tolerance of a range of reasonable views. On the scientific side, we reflect on how our uncertainty regarding the distribution of sentience in the natural world leaves us uncertain about how many claimants of justice there are and about the relative strength of their claims. We bring out some further problems with Nussbaum’s views on animal killing and pest control. We also reflect on how animal welfare science might be done differently if guided by Nussbaum’s framework.
... Because pain has been suggested for the decapods, we should examine basal crustaceans, for which ostracods or branchiopods represent extant early taxa, but we are not aware of any studies that might indicate sentience in these groups. There is also a paucity of relevant studies on primitive insects (Gibbons et al. 2022a). Basal molluscs, such as the worm-like aplacophorans, provide no evidence for sentience because these are deep-sea burrowing animals and we are not aware of suitable studies on live specimens (Wanninger and Wollesen 2019). ...
We argue that pain is not needed to protect the body from damage unless the organism is able to make free choices in action selection. Then pain (including its affective and evaluative aspects) provides a necessary prioritising motivation to select actions expected to avoid it, whilst leaving the possibility of alternative actions to serve potentially higher priorities. Thus, on adaptive grounds, only organisms having free choice over action selection should experience pain. Free choice implies actions must be selected following appraisal of their effects, requiring a predictive model generating estimates of action outcomes. These features give organisms anticipatory behavioural autonomy (ABA), for which we propose a plausible system using an internal predictive model, integrated into a system able to produce the qualitative and affective aspects of pain. Our hypothesis can be tested using behavioural experiments designed to elicit trade-off responses to novel experiences for which algorithmic (automaton) responses might be inappropriate. We discuss the empirical evidence for our hypothesis among taxonomic groups, showing how testing for ABA guides thinking on which groups might experience pain. It is likely that all vertebrates do and plausible that some invertebrates do (decapods, cephalopods and at least some insects).
... Sentience is, along these lines, often defined as the capacity of pain and suffering, and, historically, there have been doubts about whether insects can feel pain (Tiffin, 2016). However, recent studies that utilise a framework formulated by Birch et al. (2021) found evidence for the capacity to feel pain in six insect orders, including (adult) Diptera (Gibbons, Crump, et al., 2022). ...
Insect farming for animal feed production is considered a promising alternative to the traditional feed manufacturing sector, because of its low ecological footprint and circular use of required resources. However, treating insects as mini-livestock is accompanied by various questions on the suitable rearing conditions needed to achieve high-quality products, while considering insect welfare. Although there are concepts which have long served as a compass for animal welfare regulations, these have been under increasing criticism. Also, they have been drawn up for vertebrate animals and are, therefore, not entirely applicable to insects. We hold that the development of commonly accepted methods for keeping insects as mini-livestock demands deep knowledge on insect biology and a dynamic discussion on insect welfare. We plead for an evaluation of the relevant ethical and empirical aspects of insect rearing conditions and for establishing welfare criteria based on these evaluations. By addressing several questions and uncertainties from an interdisciplinary perspective of entomology, animal ethics and philosophy of mind, we argue that taking into account current knowledge on insect biology could aid in the emergence of a novel, well-informed and integrated perspective on insect welfare. Ultimately, our goal is to trace the necessary biological factors for designing implementable and appropriate insect rearing conditions, in order to avoid ethical mistakes that have historically been made in animal production systems.
... Emerging evidence supporting the potential for pain perception in insects has generated heightened awareness of their need for proper welfare and veterinary care, including appropriate means of euthanasia [1][2][3][4][5][6]. Despite this awareness and need, there is limited evidence-based data and guidance surrounding euthanasia methods in insects [6][7][8][9][10][11]. ...
Insects are commonly utilized in biomedical research and have become increasingly popular in museum collections and as pets. Despite this, objective evaluation of insect euthanasia is scarce. This study investigated the effectiveness of targeted injections of ivermectin or potassium chloride (KCl) for the euthanasia of anesthetized thorny devil stick insects (Eurycantha calcarata). Ten clinically healthy mature insects (six males, four females) were enrolled. Insects were weighed and anesthetized via exposure to a cotton ball soaked with 1.6 mL of liquid isoflurane in a 1 L sealed chamber until loss of righting reflex and response to stimulation (induction). Insects then received one of three treatments: ivermectin 100 mg/kg (n = 4), KCl 200 mEq/kg (n = 4), or 0.9% sodium chloride 100 mL/kg (n = 2) injected along the ventral thoracic midline between the first leg plate and the caudal adjacent plate. Following injection, insects were serially monitored for return of spontaneous movement and righting reflex. Death was defined as the absence of spontaneous movement for 48 h. Median (range) induction time and isoflurane concentration at induction was 36 (22-39) min (n = 9) and 22 (19-22)%, respectively. Euthanasia was successful in 4/4, 3/4, and 0/2 isoflurane-anesthetized insects receiving ivermectin, KCl, or 0.9% sodium chloride, respectively. Recovery was prolonged at 10.5 (sodium chloride female), 11.0 (KCl male), and 18.0 (sodium chloride male) hours. This is the first prospective investigation of euthanasia in adult E. calcarata. In this preliminary study, ivermectin 100 mg/kg via ventral midline injection was effective for euthanasia of thorny devil stick insects.
A recent advancement in consciousness science has been the introduction of a multidimensional framework of consciousness. This framework has been applied to global states of consciousness, including psychedelic states and disorders of consciousness, and the consciousness of non-human animals. The multidimensional framework enables a finer parsing of both various states of consciousness and forms of animal consciousness, paving the way for new scientific investigations into consciousness. In this paper, the multidimensional model is expanded by constructing temporal profiles. This expansion allows for the modelling of changes in consciousness across the life cycles of organisms and the progression over time of disorders of consciousness. The result of this expansion is 2-fold: (i) it enables new modes of comparison, both across stages of development and across species; (ii) it proposes that more attention be given to the various types of fluctuations that occur in patients who are suffering from disorders of consciousness.
We argue that it is both possible and timely to relax the assumption of anthropocentrism in agricultural and resource economics. We advocate for the incorporation of sentientist principles by including the welfare of sentient animals within the social welfare function. To exemplify this non‐anthropocentric stance, we build on our recent works that incorporate the intrinsic value of farmed animals into food production and consumption. By recognising the externalities affecting animals, we justify the implementation of specific policies, such as a meat tax, which redistributes welfare from consumers and producers to farmed animals. Furthermore, we delve into the quantitative assessment of animal welfare and demonstrate its application to food policy, revealing the substantial economic and welfare impacts at stake. Expanding on our earlier model, we also emphasize the importance of introducing a ‘sentience premium’ within species conservation policies. This additional consideration ensures that the conservation efforts appropriately account for the intrinsic value of sentient beings living in the wild.
Open research is an increasingly developed and crucial framework for the advancement of science and has seen successful adoption across a broad range of disciplines. Entomology has, however, been slow to adopt these practices compared to many adjacent fields despite ethical and practical imperatives to do so. The grand challenges facing entomology in the 21st century require synthesis of evidence at global scales, necessitating open sharing of data and research at a pace and scale incompatible with the slow adoption of open research practices. Open science also plays a vital role in fostering trust in research and maximising use of research outputs, which is ethically crucial for reducing harms to insects.
We outline these imperatives and how open research practices can enhance entomological research across a range of contexts. We also highlight the holistic nature of open science across the full research lifecycle through several specific examples of open research practices that can be adopted easily by individual entomologists. We do, however, argue that the responsibility of promoting, integrating and encouraging open research is most crucially held by publishers, including scholarly societies, which have leveraged widespread adoption in adjacent fields. Entomology must advance quickly to become a leading discipline in the open research transition.
This paper addresses a set of ideological tensions involving the classification of agential kinds, which I see as the methodological and conceptual core of the sentience discourse. Specifically, I consider ideals involved in the classification of biological and artifactual kinds, and ideals related to agency, identity, and value. These ideals frame the background against which sentience in Artificial Intelligence (AI) is theorized and debated, a framework I call the AIdeal. To make this framework explicit, I review the historical discourse on sentience as it appears in ancient, early modern, and the 20th century philosophy, paying special attention to how these ideals are projected onto artificial agents. I argue that tensions among these ideals create conditions where artificial sentience is both necessary and impossible, resulting in a crisis of ideology. Moving past this crisis does not require a satisfying resolution among competing ideals, but instead requires a shift in focus to the material conditions and actual practices in which these ideals operate. Following Charles Mills, I sketch a nonideal approach to AI and artificial sentience that seeks to loosen the grip of ideology on the discourse. Specifically, I propose a notion of participation that deflates the sentience discourse in AI and shifts focus to the material conditions in which sociotechnical networks operate.
Yellow mealworms ( Tenebrio molitor ; Coleoptera: Tenebrionidae) are currently the most farmed holometabolous insect species in the insects as food and feed industry, with over 300 billion individual mealworms reared annually. Yellow mealworm larvae are being developed for potential uses as human protein, pet, livestock and fish feed, reclamation of mycotoxin-contaminated grains, and more. Insect welfare is of great interest to consumers, producers, and academics; yet no studies have considered the species-specific welfare concerns of farmed yellow mealworms under current industry conditions. Following a model for considering farmed insect welfare, we review yellow mealworm biology and its relationships to welfare in commercial rearing facilities, including: interspecific interactions (predators, parasites, and pathogens), abiotic conditions (temperature, hydration, atmospheric gasses, lighting), nutrition (including pollutants, plastics, and hormones), intraspecific concerns (genetics, morphological defects, cannibalism, density, mating and oviposition needs, and handling-associated stress), and slaughter and depopulation methods (including anesthesia and stunning). From this review, we identify practical recommendations for improving current welfare concerns in the industry and mitigating future concerns that may appear as the industry continues to grow. Finally, we discuss future research directions that are necessary to better understand the welfare of this species.
Background: With over 1060 species reported and a considerable number of these kept in captivity, theraphosid spiders, also known as tarantulas, have become a significant part of private and zoological collections, hence necessitating a greater demand for veterinary expertise.
Aim of the article: This comprehensive review addresses the unique challenges in tarantula care. It delves into the application of diagnostic tools like histology, radiography, haematology and microbiology in tarantulas, and discusses how to gather clinically relevant data for effective treatment planning of common conditions. It also outlines adaptations to cater treatments to tarantulas' unique anatomy, and offers guidance on drug selection and veterinary procedures, as well as covering humane euthanasia methods.
Deciphering the neural basis of subjective experience remains one of the great challenges in the natural sciences. The structural complexity and the limitations around invasive experimental manipulations of the human brain have impeded progress towards this goal. While animals cannot directly report first-person subjective experiences, their ability to exhibit flexible behaviours such as motivational trade-offs are generally considered evidence of sentience. The worm Caenorhabditis elegans affords the unique opportunity to describe the circuitry underlying subjective experience at a single cell level as its whole neural connectome is known and moreover, these animals exhibit motivational trade-offs. We started with the premise that these worms were sentient and then sought to understand the neurons that were both necessary and sufficient for a motivational trade-off involving the rewarding experience of food and the negative experience of an aversive odour. A simple hierarchical network consisting of two chemosensory neurons and three interneurons was found to produce an output to motoneurons that enabled worms to respond in a contextually appropriate manner to an aversive odour according to the worm's hunger state. Given that this circuitry is like that found in the human spinal cord, retina, and primary visual cortex, three regions which are neither necessary nor sufficient for subjective experience, we conclude that motivational trade-offs are not a criterion for subjective experience in worms. Furthermore, once the neural substrate for a behaviour is described, we question the explanatory role of subjective experience in behaviour.
This book offers a phenomenological perspective on the criminal law debate on robots. Today, robots are protected in some form by criminal law. A robot is a person’s property and is protected as property. This book presents the different rationale for protecting robots beyond the property justification based on the phenomenology of human-robot interactions. By focusing on robots that have bodies and act in the physical world in social contexts, the work provides an assessment of the issues that emerge from human interaction with robots, going beyond perspectives focused solely on artificial intelligence (AI). Here, a phenomenological approach does not replace ontological concerns, but complements them. The book addresses the following key areas: Regulation of robots and AI; Ethics of AI and robotics; and philosophy of criminal law.
It will be of interest to researchers and academics working in the areas of Criminal Law, Technology and Law and Legal Philosophy.
Climate change, agricultural intensification, and other anthropogenic ecosystem challenges have caused declines in the diversity and abundance of insect pollinators. In response to these declines, entomologists have called for greater attention to insect pollinator conservation. Conservation primarily aims to protect groups of non-human animals—populations or species—with only secondary concern for the welfare of individual animals. While conservation and animal welfare goals are sometimes aligned, they often are not. And because animal welfare comes second, it tends to be sacrificed when in tension with conversation priorities. Consider, for example, lethal sampling to monitor many pollinator populations. Growing evidence suggests that the welfare of individual insect pollinators may be morally significant, particularly in the Hymenoptera and Diptera. Considering insect welfare in conservation practices and policies presents many challenges as, in the face of rapid, anthropogenic change, it may be impossible to avoid harming individual animals while promoting diverse populations. We suggest some practical, implementable strategies that can allow for more robust integration of animal welfare goals into insect pollinator conservation. By following these strategies, entomologists may be able to find policies and practices that promote the health of ecosystems and the individual animals within them.
The role of awareness and its impact on learning the conditioned eyeblink response was investigated in both trace and delay discrimination eyeblink conditioning in young and aging participants, in 4 paradigms: delay 750, delay 1250, trace 500, and trace 1000. Participants concurrently watched a silent movie about which they were questioned afterward. Acquisition in both the trace and delay discrimination task was correlated with awareness of conditioning stimulus contingencies, regardless of age. Age-dependent deficits were observed in trace discrimination but not in delay discrimination, with more severe deficits appearing at the longer trace interval. The percentage of aware participants was also found to be greater in the young population than in the aging population. These results indicate that awareness or knowledge of stimulus contingencies may be an important contributor to successful acquisition in higher order discrimination tasks.
The global Insects as Food and Feed (IAFF) industry currently farms over a trillion individual insects a year and is growing rapidly. Intensive animal production systems are known to cause a range of negative affective states in livestock; given the potential scale of the IAFF industry, it is urgent to consider the welfare of the industry’s insect livestock. The majority of the literature on farmed insect welfare has focused on: (i) establishing that insect welfare ought to be of concern; or (ii) extending vertebrate welfare frameworks to insects. However, there are many overlooked challenges to studying insect welfare and applying that knowledge in IAFF industry contexts. Here, we briefly review five of these challenges. We end with practical recommendations for the future study of insect welfare.
Over two hundred billion black soldier flies (BSF, Hermetia illucens (Diptera: Stratiomyidae)) are reared annually across the globe, with the industry projected to grow substantially in the coming decade. Black soldier flies are being actively explored across the globe for use as livestock feed; fishmeal replacements; biodiesel; human, animal, and food waste management; and even sustainable human protein. Despite the huge number of individual insects reared and interest in BSF welfare by numerous producers and academics, there is no paper that considers the species-specific welfare of BSF in farmed conditions. We review factors that relate to BSF welfare in commercial rearing facilities, including: diseases/parasites, abiotic conditions (temperature, humidity/moisture, substrate aeration, light, pupation substrates, and adult spatial needs), adult and larval nutritional considerations, injury and crowding, handling-associated stress, selective breeding and genetic modification, environmental contaminants, and slaughter methods. We conclude with a discussion of the most pressing welfare concerns for the industry, recommendations for altering the conditions that give rise to them, and suggestions for future research directions that would lend valuable insights to BSF welfare. While this summary is BSF-centric, the core topic of animal welfare applies to all insect models currently, or in the future, produced as food and feed.
The parasitoid wasp Ampulex compressa envenomates the brain of its host the American cockroach (Periplaneta americana), thereby making it a behaviorally compliant food supply for its offspring. The target of venom injection is a locomotory command center in the brain called the central complex. In this study, we investigate why stung cockroaches do not respond to injuries incurred during the manipulation process by the wasp. In particular, we examine how envenomation compromises nociceptive signaling pathways in the host. Noxious stimuli applied to the cuticle of stung cockroaches fail to evoke escape responses, even though nociceptive interneurons projecting to the brain respond normally. Hence, while nociceptive signals are carried forward to the brain, they fail to trigger robust nocifensive behavior. Electrophysiological recordings from the central complex of stung animals demonstrate decreases in peak firing rate, total firing, and duration of noxious-evoked activity. The single parameter best correlated with altered noxious-evoked behavioral responses of stung cockroaches is reduced duration of the evoked response in the central complex. Our findings demonstrate how the reproductive strategy of a parasitoid wasp is served by venom-mediated elimination of aversive, nocifensive behavior in its host.
To navigate towards a food source, animals frequently combine odor cues about source identity with wind direction cues about source location. Where and how these two cues are integrated to support navigation is unclear. Here we describe a pathway to the Drosophila fan-shaped body that encodes attractive odor and promotes upwind navigation. We show that neurons throughout this pathway encode odor, but not wind direction. Using connectomics, we identify fan-shaped body local neurons called h∆C that receive input from this odor pathway and a previously described wind pathway. We show that h∆C neurons exhibit odor-gated, wind direction-tuned activity, that sparse activation of h∆C neurons promotes navigation in a reproducible direction, and that h∆C activity is required for persistent upwind orientation during odor. Based on connectome data, we develop a computational model showing how h∆C activity can promote navigation towards a goal such as an upwind odor source. Our results suggest that odor and wind cues are processed by separate pathways and integrated within the fan-shaped body to support goal-directed navigation.
Ethical and regulatory oversight of research animals is focused on vertebrates and rarely includes invertebrates. Our aim was to undertake the first study to describe differences in public confidence, trust, and expectations for the oversight of scientists using animals in research. Participants were presented with one of four treatments using a 2 by 2 design; terrestrial (T; mice and grasshoppers) vs. aquatic (A; zebrafish and sea stars) and vertebrates (V; mice and zebrafish) vs. invertebrates (I; grasshoppers and sea stars). A representative sample of census-matched Canadian participants (n = 959) stated their confidence in oversight, trust in scientists and expectation of oversight for invertebrates on a 7-point Likert scale. Participants’ open-ended text reasoning for confidence and expectations of oversight were subjected to thematic analysis. Participants believed invertebrates should receive some level of oversight but at two-thirds of that currently afforded to vertebrates. Four primary themes emerged to explain participant expectation: (1) value of life, (2) animal experience, (3) participant reflection, and (4) oversight system centered. Confidence in oversight was highest for TV (mean ± SE; 4.5 ± 0.08) and AV (4.4 ± 0.08), less for TI (3.8 ± 0.10), and least for AI (3.5 ± 0.08), indicating the absence of oversight decreased public confidence. Four themes emerged to explain participant confidence, centered on: (1) animals, (2) participant reflection, (3) oversight system, and (4) science. Trust in scientists was similar for TV (4.3 ± 0.07) and AV (4.2 ± 0.07), but higher for TV compared to TI (4.1 ± 0.07) and TV and AV compared to AI (4.0 ± 0.06); absence of oversight decreased public trust in scientists. These results, provide the first evidence that the public believe invertebrates should receive some level of oversight if used for scientific experiments. The gap that exists between current and public expectations for the oversight of invertebrates may threaten the social licence to conduct scientific research on these animals.
The mass rearing of insects as animal feed is a new and rapidly growing component of circular agriculture, which offers the opportunity to develop it in such a way that it promotes insect health and welfare. Behaviour is an important indicator of animal performance and welfare. In this review, we synthesise the current behavioural knowledge on two saprophytic dipteran species that are increasingly being used as mini-livestock, the black soldier fly (Hermetia illucens) and the housefly (Musca domestica). We evaluate which behaviours need to be considered to optimise insect production and welfare under mass-rearing conditions. We distinguish between the different life stages (adults and larvae), and describe their feeding behaviour, social interactions (adult mating, larval aggregation), oviposition behaviour and possible cannibalism. For each species, we review what is known about these behaviours in natural environments, and how this is affected by abiotic factors or interactions with conspecifics and heterospecifics. We also address how the flies’ microbiome and pathogens can influence various aspects of behaviour. Notable differences in natural behaviours between the two species, such as their courtship and mating behaviour and the larval distribution within feed substrates are identified. These behavioural differences have important implications for how we should rear the two fly species in industrial settings, as a mismatch in mass-rearing conditions may induce environmental stress or compromise insect productivity and welfare. Escape behaviour, larval aggregation behaviour, possibly cannibalism in the larval stage and mating frequency and reproduction rate are identified as behaviours providing information on welfare of larval and adult flies. Finally, a number of aspects are identified for which behavioural knowledge is currently still sparse, while this may be important to safeguard insect welfare. We conclude with recommendations for future research to promote insect welfare.
Insects are traditionally thought to respond to noxious stimuli in an inflexible manner, without the ability to modulate their behavior according to context. We investigated whether bumblebees’ attraction to high sucrose solution concentrations reduces their avoidance of noxious heat. Bees were given the choice between either unheated or noxiously heated (55 °C) feeders with different sucrose concentrations and marked by different colors. Bees avoided noxious feeders when the unheated feeders contained high sucrose concentrations, but progressively increased feeding from noxious feeders when the sucrose concentration at unheated feeders decreased. This shows a motivational trade-off of nociceptive responses. Bees used learned color cues for their decisions, and thus the trade-off was based on processing in the brain, rather than just peripheral processing. Therefore, bees can use contextual information to modulate nociceptive behavior. This ability is consistent with a capacity for pain experiences in insects.
Modulation of nociception allows animals to optimize chances of survival by adapting their behaviour in different contexts. In mammals, this is executed by neurons from the brain and is referred to as the descending control of nociception. Whether insects have such control, or the neural circuits allowing it, has rarely been explored. Based on behavioural, neuroscientific and molecular evidence, we argue that insects probably have descending controls for nociception. Behavioural work shows that insects can modulate nocifensive behaviour. Such modulation is at least in part controlled by the central nervous system since the information mediating such prioritization is processed by the brain. Central nervous system control of nociception is further supported by neuroanatomical and neurobiological evidence showing that the insect brain can facilitate or suppress nocifensive behaviour, and by molecular studies revealing pathways involved in the inhibition of nocifensive behaviour both peripherally and centrally. Insects lack the endogenous opioid peptides and their receptors that contribute to mammalian descending nociception controls, so we discuss likely alternative molecular mechanisms for the insect descending nociception controls. We discuss what the existence of descending control of nociception in insects may reveal about pain perception in insects and finally consider the ethical implications of these novel findings.
Psilocybin has been shown to be a powerful, long-lasting antidepressant in human clinical trials and in rodent models. Although rodents have commonly been used to model psychiatric disorders, Drosophila have neurotransmitter systems similar to mammals and many comparable brain structures involved in similar behaviors. The forced swim test (FST), which has been used extensively to evaluate compounds for antidepressant efficacy, has recently been adapted for Drosophila. The fly FST has potential to be a cost-effective, high-throughput assay for evaluating potential antidepressants. For this study we pharmacologically validated the fly FST using methamphetamine, DL-α-methyltyrosine, and the antidepressant citalopram. While methamphetamine and DL-α-methyltyrosine altered overall locomotor activity in the Drosophila Activity Monitor System (DAMS), they had no significant impact on measures of immobility in the FST. Conversely, chronic citalopram decreased measures of immobility in the FST in both sexes without increasing DAMS activity. We used the validated FST to evaluate the antidepressant-like effects of high (3.5 mM) and low (0.03 mM) doses of psilocybin. Both doses of psilocybin significantly reduced measures of immobility in male flies, but not females. 0.03 mM had an effect size comparable to chronic citalopram, and 3.5 mM had an effect size approximately twice that of chronic citalopram.
Inhalation anesthetics isoflurane and sevoflurane have been widely used in clinical practice for anesthesia. However, the molecular mechanisms underlying the faster recovery from sevoflurane anesthesia than isoflurane anesthesia remain largely undetermined. Herein, we use RNA-seq, RNA interference, quantitative real-time PCR and western blotting to explore the mechanisms of recovery from isoflurane and sevoflurane anesthesia in the migratory locusts. Although the migratory locusts show similar anesthetic responses to these two chemicals in corresponding half-maximal effective concentrations (EC50s), the recovery from sevoflurane anesthesia is significantly faster than that for isoflurane anesthesia after 30 min of anesthetic exposure. Transcriptome analysis shows that those transcripts involved in cytoskeletal components, Janus kinase (JAK) pathway and cuticle protein are differentially expressed in locust brains in response to isoflurane and sevoflurane. RNAi knockdown confirms that Actin , Myosin-like protein 84B ( Mlp84B ), JAK and cuticle protein NCP56 do not affect anesthetic response of the locusts to these two chemical anesthetics. Moreover, actin , Mlp84B and NCP56 do not affect differential recovery from isoflurane and sevoflurane anesthesia, whereas RNAi knockdown of JAK and its partner STAT5B does not affect anesthetic recovery from isoflurane but elongates recovery duration from sevoflurane anesthesia. Thus, JAK may mediate faster recovery from sevoflurane anesthesia than from isoflurane anesthesia in the migratory locust. This finding provides novel insights into the molecular mechanism underlying faster recovery from sevoflurane anesthesia than isoflurane anesthesia.
The study of sensory systems in insects has a long-spanning history of almost an entire century. Olfaction, vision, and gustation are thoroughly researched in several robust insect models and new discoveries are made every day on the more elusive thermo- and mechano-sensory systems. Few specialized senses such as hygro- and magneto-reception are also identified in some insects. In light of recent advancements in the scientific investigation of insect behavior, it is not only important to study sensory modalities individually, but also as a combination of multimodal inputs. This is of particular significance, as a combinatorial approach to study sensory behaviors mimics the real-time environment of an insect with a wide spectrum of information available to it. As a fascinating field that is recently gaining new insight, multimodal integration in insects serves as a fundamental basis to understand complex insect behaviors including, but not limited to navigation, foraging, learning, and memory. In this review, we have summarized various studies that investigated sensory integration across modalities, with emphasis on three insect models (honeybees, ants and flies), their behaviors, and the corresponding neuronal underpinnings.
Two forms of associative learning—delay conditioning and trace conditioning—have been widely investigated in humans and higher-order mammals¹. In delay conditioning, an unconditioned stimulus (for example, an electric shock) is introduced in the final moments of a conditioned stimulus (for example, a tone), with both ending at the same time. In trace conditioning, a ‘trace’ interval separates the conditioned stimulus and the unconditioned stimulus. Trace conditioning therefore relies on maintaining a neural representation of the conditioned stimulus after its termination (hence making distraction possible²), to learn the conditioned stimulus–unconditioned stimulus contingency³; this makes it more cognitively demanding than delay conditioning⁴. Here, by combining virtual-reality behaviour with neurogenetic manipulations and in vivo two-photon brain imaging, we show that visual trace conditioning and delay conditioning in Drosophila mobilize R2 and R4m ring neurons in the ellipsoid body. In trace conditioning, calcium transients during the trace interval show increased oscillations and slower declines over repeated training, and both of these effects are sensitive to distractions. Dopaminergic activity accompanies signal persistence in ring neurons, and this is decreased by distractions solely during trace conditioning. Finally, dopamine D1-like and D2-like receptor signalling in ring neurons have different roles in delay and trace conditioning; dopamine D1-like receptor 1 mediates both forms of conditioning, whereas the dopamine D2-like receptor is involved exclusively in sustaining ring neuron activity during the trace interval of trace conditioning. These observations are similar to those previously reported in mammals during arousal⁵, prefrontal activation⁶ and high-level cognitive learning7,8.
For prevalent livestock, animal welfare is important to consumers. With increasing interest in edible insects, one might wonder how this concern translates to consumers’ perceptions of the welfare of insects. Therefore, we focus on consumers’ acceptance of how edible insects are currently produced. We first define what animal welfare means for prevalent livestock and transfer relevant aspects to the welfare of insects. Then, we review relevant aspects that shape consumers’ understanding of animal welfare. We provide an overview of the few consumer studies on insect welfare. Last, we present the public discourse on insects and discuss how this might be relevant to consumers’ perceptions of insect welfare.
Open access at : https://www.mdpi.com/2075-4450/13/2/121
The central complex of the insect midbrain is thought to coordinate insect guidance strategies. Computational models can account for specific behaviours but their applicability across sensory and task domains remains untested. Here we assess the capacity of our previous model (Sun et al., 2020) of visual navigation to generalise to olfactory navigation and its coordination with other guidance in flies and ants. We show that fundamental to this capacity is the use of a biologically-plausible neural copy-and-shift mechanism that ensures sensory information is presented in a format compatible with the insect steering circuit regardless of its source. Moreover, the same mechanism is shown to allow the transfer cues from unstable/egocentric to stable/geocentric frames of reference providing a first account of the mechanism by which foraging insects robustly recover from environmental disturbances. We propose that these circuits can be flexibly repurposed by different insect navigators to address their unique ecological needs.
In insects, neuronal responses to clean air have so far been reported only episodically in moths. Here we present results obtained by fast two-photon calcium imaging in the honey bee Apis mellifera, indicating a substantial involvement of the antennal lobe, the first olfactory neuropil, in the processing of mechanical stimuli. Clean air pulses generate a complex pattern of glomerular activation that provides a code for stimulus intensity and dynamics with a similar level of stereotypy as observed for the olfactory code. Overlapping the air pulses with odor stimuli reveals a superposition of mechanosensory and odor response codes with high contrast. On the mechanosensitive signal, modulations were observed in the same frequency regime as the oscillatory motion of the antennae, suggesting a possible way to detect odorless airflow directions. The transduction of mechanosensory information via the insect antennae has so far been attributed primarily to Johnston’s organ in the pedicel of the antenna. The possibility that the antennal lobe activation by clean air originates from Johnston’s organ could be ruled out, as the signal is suppressed by covering the surfaces of the otherwise freely moving and bending antennae, which should leave Johnston’s organ unaffected. The tuning curves of individual glomeruli indicate increased sensitivity at low-frequency mechanical oscillations as produced by the abdominal motion in waggle dance communication, suggesting a further potential function of this mechanosensory code. The discovery that the olfactory system can sense both odors and mechanical stimuli has recently been made also in mammals. The results presented here give hope that studies on insects can make a fundamental contribution to the cross-taxa understanding of this dual function, as only a few thousand neurons are involved in their brains, all of which are accessible by in vivo optical imaging.
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.
Animal behavior is shaped both by evolution and by individual experience. Parallel brain pathways encode innate and learned valences of cues, but the way in which they are integrated during action-selection is not well understood. We used electron microscopy to comprehensively map with synaptic resolution all neurons downstream of all Mushroom Body output neurons (encoding learned valences) and characterized their patterns of interaction with Lateral Horn neurons (encoding innate valences) in Drosophila larva. The connectome revealed multiple convergence neuron types that receive convergent Mushroom Body and Lateral Horn inputs. A subset of these receives excitatory input from positive-valence MB and LH pathways and inhibitory input from negative-valence MB pathways. We confirmed functional connectivity from LH and MB pathways and behavioral roles of two of these neurons. These neurons encode integrated odor value and bidirectionally regulate turning. Based on this we speculate that learning could potentially skew the balance of excitation and inhibition onto these neurons and thereby modulate turning. Together, our study provides insights into the circuits that integrate learned and innate to modify behavior.
The multiple realizability thesis (MRT) is an important philosophical and psychological concept. It says any mental state can be constructed by multiple realizability (MR), meaning in many distinct ways from different physical parts. The goal of our study is to find if the MRT applies to the mental state of consciousness among animals. Many things have been written about MRT but the ones most applicable to animal consciousness are by Shapiro in a 2004 book called The Mind Incarnate and by Polger and Shapiro in their 2016 work, The Multiple Realization Book. Standard, classical MRT has been around since 1967 and it says that a mental state can have very many different physical realizations, in a nearly unlimited manner. To the contrary, Shapiro’s book reasoned that physical, physiological, and historical constraints force mental traits to evolve in just a few, limited directions, which is seen as convergent evolution of the associated neural traits in different animal lineages. This is his mental constraint thesis (MCT). We examined the evolution of consciousness in animals and found that it arose independently in just three animal clades—vertebrates, arthropods, and cephalopod mollusks—all of which share many consciousness-associated traits: elaborate sensory organs and brains, high capacity for memory, directed mobility, etc. These three constrained, convergently evolved routes to consciousness fit Shapiro’s original MCT. More recently, Polger and Shapiro’s book presented much the same thesis but changed its name from MCT to a “modest identity thesis.” Furthermore, they argued against almost all the classically offered instances of MR in animal evolution, especially against the evidence of neural plasticity and the differently expanded cerebrums of mammals and birds. In contrast, we argue that some of these classical examples of MR are indeed valid and that Shapiro’s original MCT correction of MRT is the better account of the evolution of consciousness in animal clades. And we still agree that constraints and convergence refute the standard, nearly unconstrained, MRT.
Ethanol consumption has been shown to have many deleterious effects, including behavioral alterations, motor deficits, reduction in inhibition, and alteration of neurochemical expression. These effects occur in the wide variety of species that consume ethanol. Although studies have examined aversive conditioning in honey bees (Apis mellifera), few have examined the role of intoxication on the acquisition of learning in such paradigms. The current study continues a line of research using honey bees as a model to explore the behavioral effects of ethanol toxicity. A passive avoidance task is used to explore how increasing dosages of ethanol affects the ability of honey bees to perform this task. The results show that honey bees exposed to higher concentrations of ethanol have slower passive avoidance acquisition than bees exposed to lower concentrations under the same conditions. Bees not experiencing aversive stimuli displayed no difference from baseline behavior when exposed to varying concentrations of ethanol. (PsycInfo Database Record (c) 2021 APA, all rights reserved).
Insect neuroscience generates vast amounts of highly diverse data, of which only a small fraction are findable, accessible and reusable. To promote an open data culture, we have therefore developed the InsectBrainDatabase ( IBdb ), a free online platform for insect neuroanatomical and functional data. The IBdb facilitates biological insight by enabling effective cross-species comparisons, by linking neural structure with function, and by serving as general information hub for insect neuroscience. The IBdb allow users to not only effectively locate and visualize data, but to make them widely available for easy, automated reuse via an application programming interface. A unique private mode of the database expands the IBdb functionality beyond public data deposition, additionally providing the means for managing, visualizing and sharing of unpublished data. This dual function creates an incentive for data contribution early in data management workflows and eliminates the additional effort normally associated with publicly depositing research data.
Maladaptive operant conditioning contributes to development of neuropsychiatric disorders. Candidate genes have been identified that contribute to this maladaptive plasticity, but the neural basis of operant conditioning in genetic model organisms remains poorly understood. The fruit fly Drosophila melanogaster is a versatile genetic model organism that readily forms operant associations with punishment stimuli. However, operant conditioning with a food reward has not been demonstrated in flies, limiting the types of neural circuits that can be studied. Here we present the first sucrose-reinforced operant conditioning paradigm for flies. In the paradigm, flies walk along a Y-shaped track with reward locations at the terminus of each hallway. When flies turn in the reinforced direction at the center of the track, they receive a sucrose reward at the end of the hallway. Only flies that rest early in training learn the reward contingency normally. Flies rewarded independently of their behavior do not form a learned association but have the same amount of rest as trained flies, showing that rest is not driven by learning. Optogenetically-induced sleep does not promote learning, indicating that sleep itself is not sufficient for learning the operant task. We validated the sensitivity of this assay to detect the effect of genetic manipulations by testing the classic learning mutant dunce. Dunce flies are learning-impaired in the Y-Track task, indicating a likely role for cAMP in the operant coincidence detector. This novel training paradigm will provide valuable insight into the molecular mechanisms of disease and the link between sleep and learning.
Evolutionary accounts of feelings, and in particular of negative affect and of pain, assume that creatures that feel and care about the outcomes of their behavior outperform those that do not in terms of their evolutionary fitness. Such accounts, however, can only work if feelings can be shown to contribute to fitness-influencing outcomes. Simply assuming that a learner that feels and cares about outcomes is more strongly motivated than one that does is not enough, if only because motivation can be tied directly to outcomes by incorporating an appropriate reward function, without leaving any apparent role to feelings (as it is done in state-of-the-art engineered systems based on reinforcement learning). Here, we propose a possible mechanism whereby pain contributes to fitness: an actor-critic functional architecture for reinforcement learning, in which pain reflects the costs imposed on actors in their bidding for control, so as to promote honest signaling and ultimately help the system optimize learning and future behavior.
Most of our knowledge of insect genomes comes from Holometabolous species, which undergo complete metamorphosis and have genomes typically under 2 Gb with little signs of DNA methylation. In contrast, Hemimetabolous insects undergo the presumed ancestral process of incomplete metamorphosis, and have larger genomes with high levels of DNA methylation. Hemimetabolous species from the Orthopteran order (grasshoppers and crickets) have some of the largest known insect genomes. What drives the evolution of these unusual insect genome sizes, remains unknown. Here we report the sequencing, assembly and annotation of the 1.66-Gb genome of the Mediterranean field cricket Gryllus bimaculatus, and the annotation of the 1.60-Gb genome of the Hawaiian cricket Laupala kohalensis. We compare these two cricket genomes with those of 14 additional insects and find evidence that hemimetabolous genomes expanded due to transposable element activity. Based on the ratio of observed to expected CpG sites, we find higher conservation and stronger purifying selection of methylated genes than non-methylated genes. Finally, our analysis suggests an expansion of the pickpocket class V gene family in crickets, which we speculate might play a role in the evolution of cricket courtship, including their characteristic chirping. Ylla, Extavour et al. use genomic data from crickets to investigate the evolution of large genome sizes and DNA methylation events in insects. Their findings indicate that transposable element activity drove genome expansion in hemimetabolous insects, such as crickets and grasshoppers, and that DNA methylation is predominant in conserved genes.
Trace conditioning involves the pairing of a neutral conditioned stimulus (CS), followed by a short interval with a motivationally significant unconditioned stimulus (UCS). Recently, trace conditioning has been proposed as a test for animal consciousness due to its correlation in humans with subjective report of the CS–UCS connection. We argue that the distractor task in the Clark and Squire (1998) study on trace conditioning has been overlooked. Attentional inhibition played a crucial role in disrupting trace conditioning and awareness of the CS–UCS contingency in the human participants of that study. These results may be understood within the framework of the Temporal Representation Theory that asserts consciousness serves the function of selecting information into a representation of the present moment. While neither sufficient nor necessary, attentional processes are the primary means to select stimuli for consciousness. Consciousness and attention are both needed by an animal capable of flexible behavioral response. Consciousness keeps track of the current situation; attention amplifies task-relevant stimuli and inhibits irrelevant stimuli. In light of these joint functions, we hypothesize that the failure to trace condition under distraction in an organism known to successfully trace condition otherwise can be one of several tests that indicates animal consciousness. Successful trace conditioning is widespread and by itself does not indicate consciousness.
How subjective experience is realized in nervous systems remains one of the great challenges in the natural sciences. An answer to this question should resolve debate about which animals are capable of subjective experience. We contend that subjective experience of sensory stimuli is dependent on the brain’s awareness of its internal neural processing of these stimuli. This premise is supported by empirical evidence demonstrating that disruption to either processing streams or awareness states perturb subjective experience. Given that the brain must predict the nature of sensory stimuli, we reason that conscious awareness is itself dependent on predictions generated by hierarchically organized forward models of the organism’s internal sensory processing. The operation of these forward models requires a specialized neural architecture and hence any nervous system lacking this architecture is unable to subjectively experience sensory stimuli. This approach removes difficulties associated with extrapolations from behavioral and brain homologies typically employed in addressing whether an animal can feel. Using nociception as a model sensation, we show here that the Drosophila brain lacks the required internal neural connectivity to implement the computations required of hierarchical forward models. Consequently, we conclude that Drosophila, and those insects with similar neuroanatomy, do not subjectively experience noxious stimuli and therefore cannot feel pain.
Animals form and update learned associations between otherwise neutral sensory cues and aversive outcomes (i.e., punishment) to predict and avoid danger in changing environments. When a cue later occurs without punishment, this unexpected omission of aversive outcome is encoded as reward via activation of reward-encoding dopaminergic neurons. How such activation occurs remains unknown. Using real-time in vivo functional imaging, optogenetics, behavioral analysis and synaptic reconstruction from electron microscopy data, we identify the neural circuit mechanism through which Drosophila reward-encoding dopaminergic neurons are activated when an olfactory cue is unexpectedly no longer paired with electric shock punishment. Reduced activation of punishment-encoding dopaminergic neurons relieves depression of olfactory synaptic inputs to cholinergic neurons. Synaptic excitation by these cholinergic neurons of reward-encoding dopaminergic neurons increases their odor response, thus decreasing aversiveness of the odor. These studies reveal how an excitatory cholinergic relay from punishment- to reward-encoding dopaminergic neurons encodes the absence of punishment as reward, revealing a general circuit motif for updating aversive memories that could be present in mammals.
Leucokinins (LKs) constitute a family of neuropeptides identified in numerous insects and many other invertebrates. LKs act on G-protein-coupled receptors that display only distant relations to other known receptors. In adult Drosophila, 26 neurons/neurosecretory cells of three main types express LK. The four brain interneurons are of two types, and these are implicated in several important functions in the fly’s behavior and physiology, including feeding, sleep–metabolism interactions, state-dependent memory formation, as well as modulation of gustatory sensitivity and nociception. The 22 neurosecretory cells (abdominal LK neurons, ABLKs) of the abdominal neuromeres co-express LK and a diuretic hormone (DH44), and together, these regulate water and ion homeostasis and associated stress as well as food intake. In Drosophila larvae, LK neurons modulate locomotion, escape responses and aspects of ecdysis behavior. A set of lateral neurosecretory cells, ALKs (anterior LK neurons), in the brain express LK in larvae, but inconsistently so in adults. These ALKs co-express three other neuropeptides and regulate water and ion homeostasis, feeding, and drinking, but the specific role of LK is not yet known. This review summarizes Drosophila data on embryonic lineages of LK neurons, functional roles of individual LK neuron types, interactions with other peptidergic systems, and orchestrating functions of LK.
Sensing olfactory signals in the environment represents a crucial and significant task of sensory systems in almost all organisms to facilitate survival and reproduction. Notably, the olfactory system of diverse animal phyla shares astonishingly many fundamental principles with regard to anatomical and functional properties. Binding of odor ligands by chemosensory receptors present in the olfactory peripheral organs leads to a neuronal activity that is conveyed to first and higher-order brain centers leading to a subsequent odor-guided behavioral decision. One of the key centers for integrating and processing innate olfactory behavior is the lateral horn (LH) of the protocerebrum in insects. In recent years the LH of Drosophila has garnered increasing attention and many studies have been dedicated to elucidate its circuitry. In this review we will summarize the recent advances in mapping and characterizing LH-specific cell types, their functional properties with respect to odor tuning, their neurotransmitter profiles, their connectivity to pre-synaptic and post-synaptic partner neurons as well as their impact for olfactory behavior as known so far.
Instrumental conditioning is a crucial substrate of adaptive behaviour, allowing individuals to selectively interact with the stimuli in their environment to maximise benefit and minimise harm. The extent to which complex forms of learning, such as instrumental conditioning, are possible without conscious awareness is a topic of considerable importance and ongoing debate. In light of recent theoretical and empirical contributions casting doubt on the early demonstrations of unconscious instrumental conditioning, we revisit the question of its feasibility in two modes of conditioning. In Experiment 1, we used trace conditioning, following a prominent paradigm (Pessiglione et al., 2008) and enhancing its sensitivity. Success in this task requires participants to learn to approach reward-predictive stimuli and avoid punishment-predictive stimuli through monetary reinforcement. All stimuli were rendered unconscious using forward-backward masking. In Experiment 2, we used delay conditioning to shorten the stimulus-outcome delay, retaining the structure of the original task but presenting the stimuli under continuous flash suppression to allow for an overlap of the stimulus, action, and outcome, as well as replacing monetary reinforcement with primary appetitive reinforcement. In both experiments, we found evidence for absence of unconscious instrumental conditioning, showing that participants were unable to learn to adjust their behaviour to approach positive stimuli and avoid negative ones. This result is consistent with evidence that unconscious stimuli fail to bring about long-term behavioural adaptations, and provides empirical evidence to support theoretical proposals that consciousness might be necessary for adaptive behaviour, where selective action is required.
Making inferences about the computations performed by neuronal circuits from synapse-level connectivity maps is an emerging opportunity in neuroscience. The mushroom body (MB) is well positioned for developing and testing such an approach due to its conserved neuronal architecture, recently completed dense connectome, and extensive prior experimental studies of its roles in learning, memory and activity regulation. Here we identify new components of the MB circuit in Drosophila , including extensive visual input and MB output neurons (MBONs) with direct connections to descending neurons. We find unexpected structure in sensory inputs, in the transfer of information about different sensory modalities to MBONs, and in the modulation of that transfer by dopaminergic neurons (DANs). We provide insights into the circuitry used to integrate MB outputs, connectivity between the MB and the central complex and inputs to DANs, including feedback from MBONs. Our results provide a foundation for further theoretical and experimental work.
The larva of Drosophila melanogaster is emerging as a powerful model system for comprehensive brain-wide understanding of the circuit implementation of neural computations. With an unprecedented amount of tools in hand, including synaptic-resolution connectomics, whole-brain imaging, and genetic tools for selective targeting of single neuron types, it is possible to dissect which circuits and computations are at work behind behaviors that have an interesting level of complexity. Here we present some of the recent advances regarding multisensory integration, learning, and action selection in Drosophila larva.
The recent interest in using insects as food and feed is based on their capacity to be a sustainable alternative to other protein sources. When farmed as mini livestock, the question is raised as to whether they are ‘sentient beings’ (self-conscious)? In researching this topic, the problem is that humans often expect animals to have the same subjective experience as we do (anthropomorphic) and consider themselves as the centre of the universe (anthropocentric). We discuss insects’ sentience by looking at their brain, behaviour, and communicative abilities. The miniature brains of insects seem to be arranged in a very efficient functional way due to their very long evolutionary history. As for their behaviour, insects are capable of social and associative learning. Even dopamine, a neurotransmitter involved in reward and pleasure, plays a role. Human communication is mainly verbal, while for insects other means of information exchange are more important, such as tactile, chemical, visual, and vibrational. The distinction needs to be made between nociception and pain, the latter being an emotional experience. It is difficult to prove that insects can experience pain, although they have a large repertoire of withdrawal and defensive behavioural responses. The philosophical attitudes deal with how we view insects and their relations to humans. This also determines the ethical attitude and how we should treat them. Are they just there for our benefit or do we consider them as co-animals? Insects as food requires that many insects must be killed. However, the number killed may not be different when one chooses a plant-based diet. It is concluded that insects should be farmed and killed using the precautionary principle, which assumes that they can experience pain. To discuss the consequences for the industry sector that produces insects for food and feed, we used Brambell’s five freedoms as a framework.
Somatostatin is an important mood and pain-regulating neuropeptide, which exerts analgesic, anti-inflammatory, and antidepressant effects via its Gi protein-coupled receptor subtype 4 (SST4) without endocrine actions. SST4 is suggested to be a unique novel drug target for chronic neuropathic pain, and depression, as a common comorbidity. However, its neuronal expression and cellular mechanism are poorly understood. Therefore, our goals were (i) to elucidate the expression pattern of Sstr4/SSTR4 mRNA, (ii) to characterize neurochemically, and (iii) electrophysiologically the Sstr4/SSTR4-expressing neuronal populations in the mouse and human brains. Here, we describe SST4 expression pattern in the nuclei of the mouse nociceptive and anti-nociceptive pathways as well as in human brain regions, and provide neurochemical and electrophysiological characterization of the SST4-expressing neurons. Intense or moderate SST4 expression was demonstrated predominantly in glutamatergic neurons in the major components of the pain matrix mostly also involved in mood regulation. The SST4 agonist J-2156 significantly decreased the firing rate of layer V pyramidal neurons by augmenting the depolarization-activated, non-inactivating K+ current (M-current) leading to remarkable inhibition. These are the first translational results explaining the mechanisms of action of SST4 agonists as novel analgesic and antidepressant candidates.
The Western honey bee, Apis mellifera, is an important species in providing honey and pollination services globally. The mite Varroa destructor is the major threat to A. mellifera, and it is associated with the severe colony winter mortality reported in recent decades. However, Varroa mite tolerant or resistant populations of A. mellifera have been detected around the world. A proposed mechanism responsible for limiting mite population growth in the colonies is grooming behavior, the physical removal and injury of mites from the adult bee bodies by individual workers or by their nest-mates. This behavioral strategy has been poorly studied in V. destructor-resistant colonies worldwide, especially in honey bee populations of European origin. In Argentina, honey bee stocks showing survival without mite treatment have been reported. In the present study, European-derived A. mellifera populations established in the Transition Chaco eco-region (Santa Fe province), with a subtropical climate, were characterized at the colony level. A honey bee stock showing natural Varroa-resistance (M) was compared to a Varroa-susceptible stock (C) for parameters of colony status (colony strength, percentage of Varroa infestation in adults and brood, hygienic behavior) and for indirect measures of grooming (percentage of fallen mites and damaged mites). M colonies showed lower phoretic and brood infestation and higher hygienic behavior in early autumn, and higher survival and population strength after wintering, in comparison with C colonies. The mean percentages of fallen mites and of damaged mites, and the injury to mites were higher in M than in C colonies. Our results suggest that, by modulating the parasitization dynamics in colonies, grooming behavior would be associated with the higher survival of Varroa-resistant stock. This study sheds light on how honey bee colonies can adaptively respond to mite pressure by modeling their behavior to resist Varroosis and provides evidence for grooming as an emerging factor evolving by natural selection. Percentage of damaged mites appears to be a reliable measure to enhance this behavior in honey bee colonies by selective breeding. Finally, the importance of improving and protecting locally adapted honey bee populations with natural Varroa resistance for regional apiculture is discussed.
We outline a framework for evaluating scientific evidence of sentience, focusing on pain experience. It includes eight neural and cognitive-behavioural criteria, with confidence levels for each criterion reflecting the reliability and quality of the evidence. We outline the rationale for each criterion and apply our framework to a controversial sentience candidate: decapod crustaceans. We have either high or very high confidence that true crabs (infraorder Brachyura) satisfy five criteria, amounting to strong evidence of sentience. Moreover, we have high confidence that both anomuran crabs (infraorder Anomura) and astacid lobsters/crayfish (infraorder Astacidea) meet three criteria—substantial evidence of sentience. The case is, as yet, weaker for other infraorders, such as penaeid shrimps, highlighting important research gaps. Having demonstrated our framework’s application to decapod crustaceans, we hope that future research will apply it to other taxa.
Insect brains are formed by conserved sets of neural lineages whose fibers form cohesive bundles with characteristic projection patterns. Within the brain neuropil, these bundles establish a system of fascicles constituting the macrocircuitry of the brain. The overall architecture of the neuropils and the macrocircuitry appear to be conserved. However, variation is observed, for example, in size, shape, and timing of development. Unfortunately, the developmental and genetic basis of this variation is poorly understood, although the rise of new genetically tractable model organisms such as the red flour beetle Tribolium castaneum allows the possibility to gain mechanistic insights. To facilitate such work, we present an atlas of the developing brain of T. castaneum, covering the first larval instar, the prepupal stage, and the adult, by combining wholemount immunohistochemical labeling of fiber bundles (acetylated tubulin) and neuropils (synapsin) with digital 3D reconstruction using the TrakEM2 software package. Upon comparing this anatomical dataset with the published work in Drosophila melanogaster, we confirm an overall high degree of conservation. Fiber tracts and neuropil fascicles, which can be visualized by global neuronal antibodies like antiacetylated tubulin in all invertebrate brains, create a rich anatomical framework to which individual neurons or other regions of interest can be referred to. The framework of a largely conserved pattern allowed us to describe differences between the two species with respect to parameters such as timing of neuron proliferation and maturation. These features likely reflect adaptive changes in developmental timing that govern the change from larval to adult brain.
We consider the relationship between neural and behavioural evidence for animal consciousness. We critically examine two recent studies: one neural and one behavioural. The first, on crows, finds different neural activity depending on whether a stimulus is reported as seen or unseen. However, to implicate this neural activity in consciousness, we must assume that a specific conditioned behaviour is a report of conscious experience. The second study, on macaques, records behaviours strikingly similar to patterns of conscious and unconscious perception in humans. However, confounds are only ruled out in human subjects, presupposing substantial neural similarity between humans and macaques. Taken together, the two studies reveal a sense in which neural and behavioural research rely on each other. Looking ahead, these two types of evidence could prove to be either mutually reinforcing or mutually undermining. The science of animal consciousness needs both neural and behavioural evidence, ideally obtained as part of a single coordinated programme.
Identifying which nonhuman animal species are capable of feeling pain is important both for understanding pain mechanisms more generally and for informing animal welfare regulations, particularly in genera that are not yet widely protected. A common way to try to provide evidence of pain experiences is through behavioral indicators. In this paper I use a very simple interventionist approach to experimentation, and the contrast case provided by C. elegans, to argue that behavioral indicators commonly used for identifying pain in nonhuman animals are much less robust than typically presented. Indeed, I argue that many behavioral indicators of pain are invalid as they are currently described. More positively, this analysis makes it possible to identify what valid criteria might look like, and where relevant, to identify existing evidence related to them. Based on this I propose that the best way to make progress on questions around animal pain is to clearly ally them with questions about animal consciousness more generally, and to productively use conceptual and empirical work in both areas to develop more theoretically defensible behavioral indicators.
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.
Learning of chemical stimuli by insects can occur during the larval or adult life stage, resulting in changes in the imago chemotaxic behaviour. There is little information on learning in Tortricidae, and associative learning through metamorphosis is unknown in this group. Here, we evaluate the influence of olfactory aversive learning in Grapholita molesta (Busck) (Lepidoptera: Tortricidae) during the immature stage and determine if memory persists after metamorphosis. Larvae (10–12 days old) were conditioned to associate the odour of ethyl acetate with pulses of aversive electric shock. Insects were exposed to air, to the ethyl acetate odour, and to shock, in isolation or combination. After conditioning, both larvae and adults were tested in a two-choice olfactometer. Larvae exposed only to air or ethyl acetate increased legibility. Larvae trained with ethyl acetate and shock simultaneously exhibited significant avoidance to ethyl acetate. Avoidance was still present for at least 72 hours after metamorphosis. Thus, G. molesta has the ability to associate an odour to an aversive stimulus precociously, and this association is maintained through metamorphosis and persists into adulthood.
Acclimation and anesthesia are necessary steps when manipulating live honey bees, Apis mellifera, in laboratory. Although cold and carbon dioxide exposure are commonly used to temporarily immobilize honey bees, they are known to influence the bees’ physiology and behavior in various ways. We investigated the effect of captivity conditions and anesthesia methods on the non-flight metabolic rate in honey bee foragers under different ambient temperatures (25, 30, or 35 °C) by using flow-through respirometry. Honey bees experienced a significant drop in metabolic rate as they acclimate to captivity at normal laboratory temperature (25 °C), but did not show much change at higher temperatures. We found that cold and carbon dioxide exposure greatly affected honey bees’ metabolic rates during and after recovery from the anesthesia regardless of the ambient temperatures. Compared to these traditional anesthesia methods, isoflurane at the dose tested is an alternative anesthetic with a) less effect on honey bees’ metabolic rate, b) an adjustable recovery time that depends on ambient temperature, and c) visible sign of life displayed by anesthetized honey bees.
This study investigated the efficacy of isoflurane in Madagascar hissing cockroaches (Gromphadorhina portentosa). Cockroaches (n = 12) were placed in a 2-L anesthesia chamber with isoflurane initiated at 5% at 2 L/m. Movement of antennae, mandibles, and legs and righting reflex were assessed, with full induction achieved when all responses had ceased for 2 m. Cockroach movement became ataxic on average (±SD) 3.5 ± 0.9 m after isoflurane treatment, and induction occurred on average 18.7 ± 4.4 m after treatment. Loss of righting reflex was the most consistent indication of full induction. Cockroaches fully recovered on average 16.2 ± 5.6 m after removal of isoflurane inhalant. Induction was uneventful, and no mortality or obvious morbidity was observed in treated cockroaches up to 30 d posttreatment. The authors conclude that the use of inhalant isoflurane is both safe and effective for anesthesia of Madagascar hissing cockroaches.
SYNOPSIS
Locomotion is a hallmark of organisms that has enabled adaptive radiation to an extraordinarily diverse class of ecological niches, and allows animals to move across vast distances. Sampling from multiple sensory modalities enables animals to acquire rich information to guide locomotion. Locomotion without sensory feedback is haphazard, therefore sensory and motor systems have evolved complex interactions to generate adaptive behavior. Notably, sensory-guided locomotion acts over broad spatial and temporal scales to permit goal-seeking behavior, whether to localize food by tracking an attractive odor plume or to search for a potential mate. How does the brain integrate multimodal stimuli over different temporal and spatial scales to effectively control behavior? In this review, we classify locomotion into three ordinally ranked hierarchical layers that act over distinct spatiotemporal scales: stabilization, motor primitives, and higher-order tasks, respectively. We discuss how these layers present unique challenges and opportunities for sensorimotor integration. We focus on recent advances in invertebrate locomotion due to their accessible neural and mechanical signals from the whole brain, limbs and sensors. Throughout, we emphasize neural-level description of computations for multimodal integration in genetic model systems, including the fruit fly, Drosophila melanogaster, and the yellow fever mosquito, Aedes aegypti. We identify that summation (e.g. gating) and weighting—which are inherent computations of spiking neurons—underlie multimodal integration across spatial and temporal scales, therefore suggesting collective strategies to guide locomotion.