Pain in cephalopods
However, cephalopods have a special position among invertebrates in terms of their perceived ability to experience pain, which is reflected by some national and international legislation protecting them during research.
Because of the possibility that cephalopods are capable of perceiving pain, it has been suggested that "precautionary principles" should be followed with respect to human interactions and consideration of these invertebrates.
[6][7][8] In 1789, the British philosopher and social reformist, Jeremy Bentham, addressed in his book An Introduction to the Principles of Morals and Legislation the issue of our treatment of animals with the following often quoted words: "The question is not, Can they reason?
[11] In his interactions with scientists and other veterinarians, Rollin was regularly asked to "prove" that animals are conscious, and to provide "scientifically acceptable" grounds for claiming that they feel pain.
Convergent evidence indicates that non-human animals have the neuroanatomical, neurochemical, and neurophysiological substrates of conscious states along with the capacity to exhibit intentional behaviors.
[17] At the same time as the investigations using arthritic rats, studies were published showing that birds with gait abnormalities self-select for a diet that contains the painkiller carprofen.
[21][22] Veterinary articles have been published stating both reptiles[23][24][25] and amphibians[26][27][28] experience pain in a way analogous to humans, and that analgesics are effective in these two classes of vertebrates.
[34] This is the ability to detect noxious stimuli which evoke a reflex response that rapidly moves the entire animal, or the affected part of its body, away from the source of the stimulus.
Nociception usually involves the transmission of a signal along a chain of nerve fibers from the site of a noxious stimulus at the periphery to the spinal cord and brain.
In vertebrates, this process evokes a reflex arc response generated at the spinal cord and not involving the brain, such as flinching or withdrawal of a limb.
It has been argued that only primates and humans can feel "emotional pain", because they are the only animals that have a neocortex – a part of the brain's cortex considered to be the "thinking area".
There have been several published lists of criteria for establishing whether non-human animals are capable of perceiving pain, e.g.[22][36] Some criteria that may indicate the potential of another species, including cephalopods, to feel pain include:[36] The adaptive value of nociception is obvious; an organism detecting a noxious stimulus immediately withdraws the limb, appendage or entire body from the noxious stimulus and thereby avoids further (potential) injury.
The authors claim this study is the first experimental evidence to support the argument that nociceptive sensitisation is actually an adaptive response to injuries.
[39] A science-based report from the University of British Columbia to the Canadian Federal Government has been quoted as stating "The cephalopods, including octopus and squid, have a remarkably well developed nervous system and may well be capable of experiencing pain and suffering.
[3] Similarly, low-threshold mechanoreceptors and cells considered to be nociceptors in the algae octopus (Abdopus aculeatus) are sensitised for at least 24 hrs after a crushing injury.
[citation needed] In octopuses, the large optic lobes and the arms' nervous system are located outside the brain complex.
The lobe's functions include learning, memory, processing information from the various sensory modalities, control of motor responses and the blood system.
[5] The nautilus brain lacks the vertical lobe complex and is therefore simpler than that of the coleoids,[50] however, they still exhibit rapid learning (within 10 trials), and have both short- and long-term memory (as found in operant studies of cuttlefish).
"[35] Other immediate defensive behaviours that might indicate a perception of pain include inking, jetting locomotion and dymantic display.
[58] Noxious stimuli, for example electric shocks, have been used as "negative reinforcers" for training octopuses, squid and cuttlefish in discrimination studies and other learning paradigms.
It has been shown that in octopuses, electric shocks can be used to develop a passive avoidance response leading to the cessation of attacking a red ball.
[58] As in vertebrates, longfin inshore squid show sensitization of avoidance responses to tactile and visual stimuli associated with a peripheral noxious stimulus.
[46] Injured squid show trade-offs in motivation due to injury, for example, they use crypsis rather than escape behaviour when reacting to a visual threat.
For example, veined octopuses (Amphioctopus marginatus) retrieve discarded coconut shells, manipulate them, transport them some distance, and then re-assemble them to use as a shelter.
[65][69][70][71] Scientists have proposed that in conjunction with argument-by-analogy, criteria of physiology or behavioural responses can be used to assess the possibility that non-human animals can perceive pain.
[22] In 2015, Lynne Sneddon, Director of Bioveterinary Science at the University of Liverpool, published a review of the evidence gathered investigating the suggestion that cephalopods can experience pain.
Sometimes, the devices are left in situ for several days thereby preventing feeding and provoking the trapped animals to fight with each other, potentially causing suffering from discomfort and stress.
Given the possibility that cephalopods can perceive pain, it has been suggested that precautionary principles should be applied during their interactions with humans and the consequences of our actions.
However, cephalopods have a special position among invertebrates in terms of their perceived ability to experience pain, which is reflected in some national and international legislation.
[79] The 1974 Norwegian Animal Rights Law states it relates to mammals, birds, frogs, salamander, reptiles, fish, and crustaceans, i.e. it does not include cephalopods.
