The Suffering of Invertebrates: An Approach from Animal Ethics

ILAR Journal, 2011

All animals face hazards that cause tissue damage and most have nociceptive refl ex responses that protect them from such damage. However, some taxa have also evolved the capacity for pain experience, presumably to enhance longterm protection through behavior modifi cation based on memory of the unpleasant nature of pain. In this article I review various criteria that might distinguish nociception from pain. Because nociceptors are so taxonomically widespread, simply demonstrating their presence is not sufficient. Furthermore, investigation of the central nervous system provides limited clues about the potential to experience pain. Opioids and other analgesics might indicate a central modulation of responses but often peripheral effects could explain the analgesia; thus reduction of responses by analgesics and opioids does not allow clear discrimination between nociception and pain. Physiological changes in response to noxious stimuli or the threat of a noxious stimulus might prove useful but, to date, application to invertebrates is limited. Behavior of the organism provides the greatest insights. Rapid avoidance learning and prolonged memory indicate central processing rather than simple refl ex and are consistent with the experience of pain. Complex, prolonged grooming or rubbing may demonstrate an awareness of the specifi c site of stimulus application. Tradeoffs with other motivational systems indicate central processing, and an ability to use complex information suggests suffi cient cognitive ability for the animal to have a fi tness benefi t from a pain experience. Available data are consistent with the idea of pain in some invertebrates and go beyond the idea of just nociception but are not defi nitive. In the absence of conclusive data, more humane care for invertebrates is suggested.

Animal Sentience, 2022

In 1985 Macphail proposed his Null Hypothesis that there were no qualitative differences in intelligence across vertebrate species. A recent review of the literature has found overwhelming support for his view. Studies also suggest that, with respect to cognition and the neural mechanisms that support it, the Null Hypothesis should be extended to invertebrates. We suggest, on the same premise, that the Null Hypothesis should be extended to pain sentience in invertebrates. Although few studies have been conducted, behavioural and neural evidence for pain sentience has been found in various representative invertebrate species.

While invertebrates make up the majority of animal species, their welfare is overlooked compared to the concern shown to vertebrates. This fact is highlighted by the near absence of regulations in animal research, with the exception of cephalopods in the European Union. This is often justified by assumptions that invertebrates do not experience pain and stress while lacking the capacity for higher order cognitive functions. Recent research suggests that invertebrates may be just as capable as vertebrates in experiencing pain and stress, and some species display comparable cognitive capacities. Another obstacle is the negative view of invertebrates by the public, which often regards them as pests with no individual personalities, gastronomic entities, or individuals for scientific experimentation without rules. Increasingly, studies have revealed that invertebrates possess individual profiles comparable to the personalities found in vertebrates. Given the large economic impact of invertebrates, developing certain attitude changes in invertebrate welfare may be beneficial for producers while providing higher welfare conditions for the animals. While the immense number and type of species makes it difficult to suggest that all invertebrates will benefit from increased welfare, in this review we provide evidence that the topic of invertebrate welfare should be revisited, more thoroughly investigated, and in cases where appropriate, formally instituted.

Animal Sentience, 2016

The aim of this commentary is to expand the discussion about subjective experience to other arthropods, notably crustaceans. Various species of crustaceans show responses consistent with their feeling pain. Hermit crabs also show prolonged investigation of new shells. They clearly attend to and integrate information from a wide variety of sources that enable them to evaluate the quality of the new shell relative to their current shell. These observations too are consistent with their having subjective experience.

Animals

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.

My aim in this paper is to explain a meaningful sense in which death is a misfortune for an invertebrate. The account presented is a logical implication of bringing together two distinct pieces of theory: the deprivation account of the harm of death, and the biocentric ethical theory developed by the New Zealand philosopher, Nicholas Agar. Combined, the two theories support the following thesis: death harms an invertebrate because it deprives the individual of future 'biopreference' satisfaction.

The Journal of Ethics, 2011

Diseases of Aquatic Organisms, 2007

This paper first explores 3 philosophical bases for attitudes to invertebrates, Contractarian/Kantian, Utilitarian, and Rights-based, and what they lead us to conclude about how we use and care for these animals. We next discuss the problems of evaluating pain and suffering in invertebrates, pointing out that physiological responses to stress are widely similar across the animal kingdom and that most animals show behavioral responses to potentially painful stimuli. Since cephalopods are often used as a test group for consideration of pain, distress and proper conditions for captivity and handling, we evaluate their behavioral and cognitive capacities. Given these capacities, we then discuss practical issues: minimization of their pain and suffering during harvesting for food; ensuring that captive cephalopods are properly cared for, stimulated and allowed to live as full a life as possible; and, lastly, working for their conservation.

Invertebrates have a long history of use in scientific research but there has been little concern for their welfare until very recently. Unlike vertebrate research animals, whose uses are closely regulated, invertebrate animals are minimally protected. In some countries regulations extend to a few species, but the vast majority of invertebrate animals can be used in research with no oversight, protections or legal regulation. Whether this is cause for concern depends on the ability of invertebrate animals to experience pain, suffering or distress as a result of husbandry and experimental procedures. To date there is minimal evidence that invertebrate animals are capable of experiencing such affective states, but this is largely due to very little experimental effort devoted to testing such hypotheses. In this article I review current regulatory guidelines for use of invertebrate animals and their relevance to species of varying neural and behavioural complexity. I define some simple steps that postdoctoral and other young researchers can take to improve the welfare of research animals within their own laboratories, and provide a framework for contributing more broadly to the field of welfare--based research by publishing their observations when improvements have had a positive effect on their animals and their research.

The concept of sentience, which concerns the capacity to have feelings, involves cognitive concepts and awareness. The cognitive capacities of parrots, corvids, cows, pigs and sheep are substantial. All vertebrates, including fish, are shown to have pain systems. There has been rapid development in animal welfare science, including pain assessment. Examples of new pain indicators in sheep and other species are presented.