Study of crabs suggests they are capable of feeling pain

A hermit crab
A hermit crab.

(Phys.org)—A pair of researchers with Queen's University in the U.K. has found via testing, that contrary to conventional thinking, crabs appear to be capable of feeling pain. In their paper published in the journal Biology Letters, Robert Elwood and Laura Adams describe how they subjected a group of crabs to jolts of electricity and the ways they tested them to see if the shocks elicited a pain response.

In humans and a host of other vertebrates, demonstrations of pain are obvious, from cries and moans to activities related to escape to avoidance behavior afterwards. But do invertebrates and/or fish feel pain? It is a reasonable question because of the way that some invertebrates are treated by humans—dunking them, while still alive, into a pot of boiling water, for instance. Doing so to a cow, pig or chicken would be unthinkable, yet it is done routinely with crabs and lobsters, which do generally attempt to escape their fate. The conventional view is that such creatures are not able to experience pain, at least in the sense that humans feel it, because they do not have brain parts that would appear to be able to process it. But, that may be oversimplifying things—to better define if a creature experiences pain, scientists have begun to establish rules or guidelines to help, such as noting types or degree of reactionary behavior or changes in hormone levels—if such guidelines are met, the creature can be said to feel pain, in whatever form.

In this new study, Elwood and Adams set out to determine if common crabs experience pain. To find out they obtained 40 specimens and put them in plastic tanks—all had wires attached but only 20 were actually given shocks—for 200-milliseconds every 10 seconds for a two minute period. All of the crabs were watched to observe their behavior, before, during and after the shocks were applied.

The researchers report that the shocked crabs displayed more vigorous behavior than those in the control group, which included walking around, taking a threatened posture or trying to climb out of the tank. Even more tellingly, they noted that the shocked crabs experienced spiked levels of in their haemolymph—a fluid in crabs that is analogous to blood in humans.

Taken together the evidence indicates very clearly, the team claims, that do indeed feel pain.


Explore further

'Shell-shocked' crabs can feel pain

More information: Electric shock causes physiological stress responses in shore crabs, consistent with prediction of pain, Biology Letters, Published 11 November 2015.DOI: 10.1098/rsbl.2015.0800

Abstract
Animal pain is defined by a series of expectations or criteria, one of which is that there should be a physiological stress response associated with noxious stimuli. While crustacean stress responses have been demonstrated they are typically preceded by escape behaviour and thus the physiological change might be attributed to the behaviour rather than a pain experience. We found higher levels of stress as measured by lactate in shore crabs exposed to brief electric shock than non-shocked controls. However, shocked crabs showed more vigorous behaviour than controls. We then matched crabs with the same level of behaviour and still found that shocked crabs had stronger stress response compared with controls. The finding of the stress response, coupled with previous findings of long-term motivational change and avoidance learning, fulfils the criteria expected of a pain experience.

Journal information: Biology Letters

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Nov 11, 2015
All animals experience pain as it is necessary for avoiding many types of danger.
However I feel any organism must be able to realize pain and or reflect on it consciously for anyone to claim an organism is truly experiencing pain.

Nov 11, 2015
Slow down here, does their software process stimuli? Sure, you could program a watch to "feel pain". Is their a mind in that little crabby brain that cares? Absolutely not, a crab is a biological machine. We know there's no sense of self until you get into very high end animals, like apes. I intend to gleefully continue murdering crustaceans with no qualms about their "feelings".

Nov 11, 2015
How scared we seem to be to include ourselves as animals, to fear the fact we are not much different.

Nov 11, 2015
We know there's no sense of self until you get into very high end animals, like apes. I intend to gleefully continue murdering crustaceans with no qualms about their "feelings".


Whatever helps you sleep at night. However, I don't really see why something needs a sense of self to experience pain. The crab might very well be capable of experiencing a negative qualia without attributing the experience to some vague notion of a "self".

Nov 11, 2015
The conventional view is that such creatures are not able to experience pain

I always wondered who held that 'conventional' view. Nocioception (pain awareness) is linked to the appropriate sensoric nerves (present in organs, joints and the skin).
And we know these kinds of nerves are present in other animals besides land dwelling mammals. It would be pointless of fish/crabs to have them and yet not feel pain.

A sense of self doesn't come into it. There are people with brain damage that have no sense of self - yet they do feel pain sure enough.

Nov 11, 2015
Sometimes I wonder if researchers can feel pain.

Nov 11, 2015
How scared we seem to be to include ourselves as animals, to fear the fact we are not much different.
"Those of us who have had experiences with psychopaths know that the language of the psychopath is two-dimensional. They are, as someone once said, as "deep as a thimble."

"Most people are able to combine ideas that have consistent thought themes, but psychopaths have great difficulty doing this. Again, this suggests a genetic restriction to what we have called the Juvenile Dictionary. Not only are they using extremely restricted definitions, they cannot, by virtue of the way their brains work, do otherwise. Virtually all of the research on psychopaths reveals an inner world that is BANAL, SOPHOMORIC, and DEVOID of the color and detail that generally exists in the inner world of normal people."

Nov 11, 2015
The aversion to causing pain is purely a human thing. There is no aversion to pain in Nature outside the individual feeling said pain. Many aspects of my existence cause pain and/or suffering to something. To imagine that I can exist without having some negative affect on some other living thing's ability to exist is fantasy.
Therefore I can still cook crabs, and eat them. I always knew they were pained by that anyway. I don't have the need to believe that I can live without causing pain to something.

Nov 11, 2015
Sorry z you're pretty much wrong on this. Many animals exhibit empathy.
http://news.disco...0218.htm

-And humans can exhibit a profound lack of it regarding members of other tribes, which they routinely consider somewhat less than human.

Tribalism - the Urge to Diverge and the beginning of speciation in the human animal.

Nov 11, 2015
Just because someone doesn't look like you, it doesn't mean it is ok to treat them poorly.

It saddens me how far humanity is from learning that lesson.

Nov 12, 2015
To imagine that I can exist without having some negative affect on some other living thing's ability to exist is fantasy.

Sure. But one shouldn't jump to the conclusion that since we cannot avoid all pain that all pain is therefore unavoidable. There are certainly pina scenarios which can be avoided. And it's not a bad idea to think about doing so.

On the other side of the coin: pin isn't the highest good/bad thing. Survival comes first. And we are omnivores. If we cannot avoid killing animals for food we can at least think about doing it in a 'humane' way and not the most excrutiating way possible.

Nov 12, 2015
Perhaps I should have said the aversion to causing pain to continue survival of yourself or your progeny. Humans have a tendency to project our emotions onto other living things. Humans climb into cages to pet tigers, for example. The house cat catching and eating a rabbit has no thought of the experience the rabbit is enjoying, and since the house cat does not have the demands of a wild life (economy of action reqm'nt) often prolongs the rabbit's death with play. My point is that a human is the only animal on this earth we know of that might pause to wonder if his prey feels pain, while killing to eat. I guess I was trying to stick with the subject of the article.

Nov 12, 2015
saddens me how far humanity is from learning that lesson.
It saddens me to realize how much reality needs to be distorted in order to manage human beings.

We evolved as members of tribes. Tribes were in constant conflict over resources because of our tropical birthrate, as well as our ability to hunt the predators which would normally have kept our numbers in check.

This behavior became genetic. We are genetically predisposed to identiify with a tribe, be it religious, ethnic, nationalist, economic, etc.

This is neither right nor wrong. It just IS.

However that doesnt make it right, or good for civilization.

The west is struggling to sell the idea of the universal tribe. To do this it cant tell people that prejudice and bigotry are natural but that they need to disregard these feelings; they have to be convinced that they should be ashamed for feeling them.

This is how you domesticate. It is natural for a dog to pee on the carpet or to hate cats.

Nov 12, 2015
often prolongs the rabbit's death with play
'Play' is practice, an essential process of honing motor skills and learning how prey behave. There is nothing arbitrary about it, whether it be cats or kids.

Doesnt mean its not pleasurable. The most important activities are the most pleasurable; eating, sleeping, procreating, competing, etc.
My point is that a human is the only animal on this earth we know of that might pause to wonder if his prey feels pain, while killing to eat
What makes you think this is a natural response as opposed to something walt disney taught you?

Nov 12, 2015
It is natural to try to propagate your genes no matter the cost; but we are civilized enough to not go raping everyone in sight. What is natural isn't always good, and what is better isn't always natural.

There are a lot of instincts that no longer serve us; not to mention a lot of cultural features that are detrimental to the species, not to mention the biosphere as a whole.

We are lucky to be smart enough to be able to think twice about what our instincts try to push us to do by the time we started having the power to make the world inhospitable to us. Unfortunately, not everyone is properly taking advantage of billions of years of evolution.

Having the ability to evaluate the consequences of our actions before we take them gives us the responsibility of doing the right thing.

And besides, we need to set a good example before post-singularity AIs start learning from us.

Nov 14, 2015
If we want to rise above our evolutionary roots, we would be better served by addressing our need for the capacity for self delusion. The goal of eliminating this need would indeed be an ambitious one, but a worthy one.
Ghost, I am not arguing the source of our humanity. It would not matter if Disney changes your thought process, since Disney is a part of humanity. The facts still stand. Your argument is like the exercise of trying to determine if there is a such thing as human behaviour that is not self-centered. The argument becomes circular, the chicken or the egg , and all that.
All I am saying about eating crabs, is that whether or not pain is felt in the process is more important to humans than it is to crabs. Just ask a crab.

Nov 14, 2015
... My point is that a human is the only animal on this earth we know of that might pause to wonder if his prey feels pain, while killing to eat. I guess I was trying to stick with the subject of the article.


Until we've mastered animal language or mind reading; you can't be sure we're unique. For all we know, many of them might actually be upset with what happens during feeding but lack the intellect or the knowledge (or possibly both) required to think of better ways to do it; or maybe they suffer from a compulsion like certain drug addicts that do stuff against their better judgment due to their addiction, and simply fail to have the impulse control required to act according to their conscience.

All I am saying about eating crabs, is that whether or not pain is felt in the process is more important to humans than it is to crabs. Just ask a crab.


You could only make that argument if we already knew how to speak to and understand crabs.

Nov 14, 2015
I wrote an article about this very topic 6 years ago, and I came to the same conclusion.

http://baudrunner...ain.html

Nov 15, 2015
Study of researchers discover they are capable of being stupid!

Nov 15, 2015
This article pisses me off on 3 issues.

The study "suggests": - well they either do or they don't.

Dropping crabs - like dropping IDIOT scientists, into boiling water, well they both thrash around and squeal....

And studies like these are as SANE as pouring hair dying chemicals into the eyes of rabbits, which eats the eye balls away, and they test it with Brand A, and then they test it with Brand B, which has the same fucking chemicals in it.... Like WHY?

When are we going to see tests that suggest smashing moron researchers in the face with base ball bats, could be raising their IQ, after repeating moron tests, and then publishing idiot results, that have been done many times before - about issues that are pointless and self evident in the first place.


That's how science works; you come up with an assumption and then test to see if it is right or wrong.

Nov 16, 2015
because we know pain is a basic ability needed for like everyone to survive, if the assumption was made by a sane person.

This is not true. It would be hard to argue that simple bacteria 'feel' pain rather than go for a stimulus response. There are also humans that cannot feel pain - yet they still survive (congenital analgesia), or have an illness that may destroy the ability to feel pain (e.g. leprosy).
The thing that is the object of this (and further) research is: at which part stage of the animal (or plant?) kingdom does pain awareness start?
(This is probably more of an ethical/psychological question, as I think the border is not sharply defined)

Nov 16, 2015
Wow, quite the philosophical debate. Why not just stab the crab in the brain, wait about 30 seconds, and then put him in boiling water? I do that with the fish I catch, so they should not be tortured to death, but rather killed quickly. I once cleaned crabs, which involved putting them in ice so they are lethargic, then putting on gloves and literally ripping their top shell from the bottom half. I feel some crabs grab my hand firmly. I did not like the experience, and I will not be doing that again, especially with little Blue Crabs which have like 3 ounces of meat each.

Honestly, I would think that any animal with a functioning nervous system can feel pain. Otherwise it would be easily injured and would not survive. Saying that crabs don't feel pain is a silly notion indeed.

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