So, Crabs Have Feelings?

In which the E@L considers whether invertebrates experience consciousness

Scientists used to believe that few animals were capable of experiencing pain except mammals. But that list has grown to include birds, reptiles, and amphibians, and now, maybe, fish and invertebrates.

Recently, a group of biologists, neurologists, psychologists, and philosophers drafted the New York Declaration on Animal Consciousness, which included the following statement:

“The empirical evidence indicates at least a realistic possibility of conscious experience in all vertebrates (including all reptiles, amphibians and fishes) and many invertebrates (including, at minimum, cephalopod mollusks, decapod crustaceans and insects).” 

The writers recognized that each animal’s conscious experience may be unique, and unlike what humans experience. While this statement was not intended to dictate a scientific conclusion, the writers hoped it would summarize the current state of knowledge and help provide direction for future research.

So, do piranhas process pain? Are crustaceans conscious? Do worms wonder about the world? In order to answer the question “Do fish feel pain?” we need to define pain. Fish have neurons called nociceptors that detect noxious stimuli (such as heat, laceration, mechanical or chemical stress) and allow them to respond reflexively. Such response may be expressed as physiological changes in respiration and cortisol levels, or behavioral responses to avoid or lessen the stimulus. Having a reflex is not necessarily indicative of feeling pain, however [i]. There is a distinct difference between the subjective experience of pain, and the unconscious processing of neural stimuli that may incite physiological or behavioral responses. Fish not only lack the neocortex portion of the brain that we associate with consciousness in higher animals, but they also lack many of the major neurological pathways associated with sensation of pain.

As recently as 2013, an international team of scientists concluded that:

“Fish do not have the neuro-physiological capacity for a conscious awareness of pain. In addition, behavioural reactions by fish to seemingly painful impulses were evaluated according to human criteria and were thus misinterpreted. There is still no final proof that fish can feel pain.” [ii]

Nonetheless, this does not absolve us from treating fish humanely. Current thought, though, is trending in the direction toward “fish feel pain”. In laboratory experiments, rainbow trout Oncorhynchus mykiss were injected with noxious chemicals that caused them to exhibit pain-associated symptoms such as anomalous movements, increased respiration, and rubbing their bodies against the substrate [iii]. These behaviors are alleviated by administration of morphine, suggesting that they were the result of pain rather than simple reflexes. Some countries have enacted laws supporting this view. In Germany, catching and discarding fish could subject you to a fine or incarceration.

But acknowledging the ability of animals to feel pain may be just the tip of the iceberg. Some believe that many animals may also experience a limited form of consciousness. It is well known that great apes, elephants, dolphins, and some birds are able to recognize themselves in mirrors. Horses, pigs, dogs, and other animals exhibit social behavior. Octopuses and cuttlefish have the ability to solve problems, and bees can engage in play activities. In 2012, a group of neuroscientists produced the Cambridge Declaration on Consciousness [iv] which declared that non-human animals may have the necessary physiological abilities to generate consciousness, as well as the capacity for intentional behavior, even without a neocortex.

Although studies on crustaceans are equivocal, their reactions to noxious stimuli are not inconsistent with the experience of pain. Many scientists believe we should give them the benefit of the doubt, and in 2017, Switzerland banned the practice of boiling lobsters alive without first stunning them (for example, by severing the esophageal ganglion just below the mouth). In 2018, the United Kingdom passed an Animal Welfare/Sentience Bill, declaring that all cephalopods (octopuses, cuttlefish, and the like), and decapod crustaceans (those with ten legs, including crabs, lobsters, and crayfish) should be regarded as sentient, and protected under the law. That leads us to the recent New York Declaration.

This creates a bit of a quandary for scientists. During two decades as a federal research scientist working for NOAA, I never worried about the feelings of my research subjects. My work usually involved going out on fishing boats for up to a month, catching fish, crabs, and snails, after which we counted, sexed, and measured them. If necessary, we sliced, diced, and dissected them in order to study their pathology, reproduction, or trophodynamics (food habits) before discarding the remains. On many days, we processed over a thousand fish in this manner. (This is nothing compared to how fish and crabs are handled in seafood processing plants, but that’s not today’s subject).

Studying the reproduction of king crabs required removing most of the reproductive organs, an activity much less pleasant for the crab than for me. Wrestling with a 4 kg crab during this process was challenging and potentially dangerous. The best way to dispatch them was to insert a large knife into the sternum (the crab’s “solar plexus”) which severed the ventral ganglion, the largest mass of nerve cells in their bodies, and the ones responsible for all the leg movement. Then, I cut off the legs with a large pair of bone shears, allowing the crab to die of rapid blood loss. While this may seem cruel, it was preferable to a being poked in the eye by meter-long spiny legs, or pinched by claws strong enough to snap a broomstick, and possibly losing a finger.

So, after leaving federal service for academia, it came as a rude awakening to me that such activities were highly restricted in an academic environment. Now, before I could begin any research, I needed “permission” from the University to conduct specific activities involving animals. Before I could even touch a fish, I had to submit a protocol to the Institutional Animal Care and Use Committee, otherwise known as IACUC. These protocols spelled out exactly what animals (and how many) were required for the research, why they were needed, how they would be captured, held, treated, and if necessary, euthanized.

In order to study fish trophodynamics, we needed to catch and kill fish, remove their stomachs, and identify, count, and weigh whatever they had eaten. Prior to being allowed to do that, all persons involved, including myself, grad students, and any undergraduate assistants, had to complete online training courses and acquire certifications in: Animal Use and Care, Biosafety, Aseptic Surgery Curriculum, Animal Welfare, Occupational Safety and Health, and Using Animal Subjects in Research. That’s a lot of training just to catch a fish. Furthermore, these multi-page protocols had to be submitted months before the research was conducted, and were reviewed by a committee of random professors, some of whom didn’t know the difference between a goldfish and a goldfinch.

There are good reasons to require this training. Anyone who has seen mice, rats, or rabbits kept in a research lab can appreciate that they need to be treated humanely. They need safe and comfortable conditions, adequate food and water, enough space to move around, and constant cleaning of cages, at the least. And when used for research, we are obliged to minimize any discomfort or pain that the animal might suffer. All that is well and good if you are studying warm and fuzzy vertebrates. That type of research certainly would benefit by having IACUC protections for the animals in place. But when the subject is a cold-blooded, scaly, slippery, slimy fish, are we similarly obliged?

Our academic research was almost always conducted on commercial fishing boats, where conditions were often dangerous as well as primitive (no privy), and unlike the gleaming steel and glass laboratories you might imagine. We left dock at the crack of dawn, stood outside on an open deck and bounced through the waves for hours to reach study sites 20 miles offshore. Fishermen worked frantically around us setting nets, hauling traps, and throwing fish, crabs, lobsters, or conchs into bins as fast as they could catch them. Fish were usually tossed into a large tote full of ice, whereas crabs or lobsters were thrown into the hold or another tote with only seawater. We tried to stay out of the way while carefully selecting the animals we wanted to study, then measured, dissected, and removed various organs while trying not to get seasick. Or, we just succumbed to the mal-de-mer, ran to the rail, tossed our cookies, then went back to work, still green around the gills. Sometimes we selected fish or crabs that were still alive, but often they were dead before we could get to them.

Having that experience, it was hard for me to answer with a straight face some of the questions on the IACUC form, such as “indicate method of euthanasia and disposal”, and “specify the anesthetics, analgesics, sedatives or tranquilizers that are to be used, and…the dosage and route of administration”. Truth be told, the “tranquilizer” was a tote full of ice, the “method of euthanasia” was often a conk on the head with a fish club, and the method of disposal was a sharp knife producing two fresh fish filets for dinner. That was the only way to dispatch them quickly and relatively painlessly and didn’t leave any waste. But the official answer was “Fish will be euthanized by placing on supercooled ice followed by decapitation”, as if we had a box full of dry ice and a guillotine on board. NOT.

Fortunately for me and my students, IACUC protocols were only required for research on vertebrates (e.g. fish), but not for invertebrates, so we could continue to conduct our research on crabs, lobsters, conchs, and corals, without fear of retribution from the University or grant provider. But all that may be coming to an end. Other countries are now requiring scientists to consider the welfare of not only fish, but also crustaceans and molluscs, and the US will probably soon follow suit. Not only must we minimize pain and suffering, but, according to framers of the New York Declaration, we may be required to

“…provide them with the kinds of enrichment and opportunities that allow them to express their instincts and explore their environments and engage in social systems…”. 

This leaves humans in a bit of a quandary. Looking into the eyes of an octopus, it is not difficult to visualize a molluscan mind hard at work wondering about us. Crabs and lobsters, maybe not so much. And it is even harder to extend sympathy to insects, especially disease-bearing mosquitos and crop-destroying caterpillars. And what about all those fruit flies used for genetics experiments? How do we provide them with “enrichment opportunities” and social engagement? But science, law, and ethical thought are all trending in one direction, which is to err on the side of caution, and allow the possibility that most of these animals experience not only pain, but some form of conscious awareness.

So, there you have it. Crabs, lobsters, and insects have feelings. I’ll think about that the next time I boil up a bushel of blue crabs. But I still plan to eat them.

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[i] Key B. Fish do not feel pain and its implications for understanding phenomenal consciousness. Biol Philos. 2015;30(2):149-165. doi: 10.1007/s10539-014-9469-4. Epub 2014 Dec 16. PMID: 25798021; PMCID: PMC4356734.

[ii] J D Rose, R Arlinghaus, S J Cooke, B K Diggles, W Sawynok, E D Stevens, C D L Wynne. Can fish really feel pain? Fish and Fisheries, 2012; DOI: 10.1111/faf.12010

[iii] Sneddon, L. U. 2003. The evidence for pain in fish: the use of morphine as an analgesic. Applied Animal Behaviour Science, 83(2):153-162.

[iv] Low, P. The Cambridge Declaration on Consciousness. Proceedings of the Francis Crick Memorial Conference, Churchill College, Cambridge University, July 7, 2012, pp 1-2.