Crabs 'sense and remember pain'

[Oolon Colluphid]

... according to this BBC news item (http://news.bbc.co.uk/1/hi/northern_ireland/7966807.stm):
Queen's University says new research it conducted shows crabs not only suffer pain but retain a memory of it.

The study, which looked at the reactions of hermit crabs to small electric shocks, was carried out by Professor Bob Elwood and Mirjam Appel.

The crabs reacted adversely to the shocks but also seemed to try to avoid future shocks, suggesting that they recalled the past ones.

The research is published in the journal Animal Behaviour.

Professor Elwood said the research highlighted the need to investigate how crustaceans used in food industries are treated, saying that a "potentially very large problem" was being ignored.
The article this refers to is:

Pain experience in hermit crabs?

Robert W Elwood and Mirjam Appel

Animal Behaviour, Currently "In Press, Corrected Proof, Available online 9 March 2009")
Pain may be inferred when the responses to a noxious stimulus are not reflexive but are traded off against other motivational requirements, the experience is remembered and the situation is avoided in the future.

To investigate whether decapods feel pain we gave hermit crabs, Pagurus bernhardus, small electric shocks within their shells. Only crabs given shocks evacuated their shells indicating the aversive nature of the stimulus, but fewer crabs evacuated from a preferred species of shell indicating a motivational trade-off.

Some crabs that evacuated attacked the shell in the manner seen in a shell fight. Most crabs, however, did not evacuate at the stimulus level we used, but when these were subsequently offered a new shell, shocked crabs were more likely to approach and enter the new shell. Furthermore, they approached that shell more quickly, investigated it for a shorter time and used fewer cheliped probes within the aperture prior to moving in.

Thus the experience of the shock altered future behaviour in a manner consistent with a marked shift in motivation to get a new shell to replace the one occupied. The results are consistent with the idea of pain in these animals.
Of course, in terms of this "potentially very large problem" of how "crustaceans used in food industries are treated", this does not mean they experience pain as we understand it, merely the ability to recognise and remember harmful stimuli. I mean, apart from the memory bit, snails will recoil from salt, and an accidentally bisected earthworm will apparently writhe in agony. What matters is not whether they've got nerves firing off indicating harm, but whether something's got enough brain to experience 'pain'.

Interesting though.

[premjan]

Hermit crabs are not true crabs.

[Notta]

After boiling my share of blue crabs in pots of boiling water, I can, indeed, state that crabs feel pain. Otherwise, why would they try like hell to escape the pot?

[BWE]

But it only hurts for a little bit so don't worry. :eek:

[Notta]

But it only hurts for a little bit so don't worry. :eek:They taste too good for me to worry about hurting them. Same goes for lobsters & clams.

[RAFH]

... according to this BBC news item (http://news.bbc.co.uk/1/hi/northern_ireland/7966807.stm):
Queen's University says new research it conducted shows crabs not only suffer pain but retain a memory of it.

The study, which looked at the reactions of hermit crabs to small electric shocks, was carried out by Professor Bob Elwood and Mirjam Appel.

The crabs reacted adversely to the shocks but also seemed to try to avoid future shocks, suggesting that they recalled the past ones.

The research is published in the journal Animal Behaviour.

Professor Elwood said the research highlighted the need to investigate how crustaceans used in food industries are treated, saying that a "potentially very large problem" was being ignored.
The article this refers to is:

Pain experience in hermit crabs?

Robert W Elwood and Mirjam Appel

Animal Behaviour, Currently "In Press, Corrected Proof, Available online 9 March 2009")
Pain may be inferred when the responses to a noxious stimulus are not reflexive but are traded off against other motivational requirements, the experience is remembered and the situation is avoided in the future.

To investigate whether decapods feel pain we gave hermit crabs, Pagurus bernhardus, small electric shocks within their shells. Only crabs given shocks evacuated their shells indicating the aversive nature of the stimulus, but fewer crabs evacuated from a preferred species of shell indicating a motivational trade-off.

Some crabs that evacuated attacked the shell in the manner seen in a shell fight. Most crabs, however, did not evacuate at the stimulus level we used, but when these were subsequently offered a new shell, shocked crabs were more likely to approach and enter the new shell. Furthermore, they approached that shell more quickly, investigated it for a shorter time and used fewer cheliped probes within the aperture prior to moving in.

Thus the experience of the shock altered future behaviour in a manner consistent with a marked shift in motivation to get a new shell to replace the one occupied. The results are consistent with the idea of pain in these animals.
Of course, in terms of this "potentially very large problem" of how "crustaceans used in food industries are treated", this does not mean they experience pain as we understand it, merely the ability to recognise and remember harmful stimuli. I mean, apart from the memory bit, snails will recoil from salt, and an accidentally bisected earthworm will apparently writhe in agony. What matters is not whether they've got nerves firing off indicating harm, but whether something's got enough brain to experience 'pain'.

Interesting though.

That's one of the most elitest statements I've yet to read. Pain is a very basic experience. It doesn't take brains to experience. Believe me, I've done way more than the Federally Recommended Maximum Lifetime Allowance, by a couple of orders of magnitude. To suggest organisms don't experience pain is rubbish of the highest order. It's one of the most basic sensory inputs there is.

I can't wait until you meet up with some superior intelligence who feels you lack sufficient brains to 'experience' pain. Maybe, if you scream loud enough and writhe sufficiently, you'll be able to change their minds.

[BWE]

eeewww. I can wait.

[Oolon Colluphid]

How are you defining 'experience' then?

[GenesisNemesis]

How much physical pain can they feel? As much as a human?

[Sodong]

It's an interesting question RAFH. In organisms such as ourselves and others possessing a central nervous system, the sensation of pain is initiated when receptor molecules in epithelial tissues change in response to an environmental stimulus and signal other neural cells. The signal is transmitted by nerve cells through the spinal cord and processed in several parts of the brain.

Pain perception is a fairly complex phenomenon involving all components of our nervous systems - receptors, nerves, spine, cerebrum, midbrain, thalamus and neocortex. Disabling or inhibiting nociceptor function, for example, reduces or eliminates the ability to feel pain. Organisms having a less complex nervous system may have several mechanisms for detecting and responding to noxious environmental stimuli but it seems hard to say whether or not that experience is comparable to what we experience as pain when the signal is processed differently in non-CNS sensory systems. I'm not sure that merely observing aversion is an adequate indicator of pain. Sensory pathways intended to alert organisms to some condition detrimental to survival may or may not have a similar sensation if that sensation requires complex neural processing. Be that as it may, I don't eat lobsters and don't like the thought of boiling anything alive (though I suppose it's not that qualitatively different from other methods of execution). :)

[Goldie]

Pain is merely how we describe our aversion to something which shouldn't be happening... (example: getting too close to a fire)
Why should we think this "feeling" would be perceived any differently? It's still got to be uncomfortable to create an aversion.
(Said by someone who is in constant, chronic pain.)

[Oolon Colluphid]

Well, take amoebas. Not the brightest critters on the planet, I think we can agree. Yet they exhibit tropisms: movement towards or away from stimuli. You get positive tropisms towards food materials... and negative tropisms away from poisons. Poisons are damaging. Suppose the amoeba can't get away, and is damaged by the poison, perhaps dying slowly from the damage the poison wreaks on the amoeba's cellular structure.

We've got an organism that does its best to get away from something that harms it. And our putative one here dies slowly from being damaged.

Is it in pain?

Does it die slowly and horribly?

On what grounds might we say 'yes'?

If no, what else is required in order to perceive pain in something like the way we do?

And how much of those 'something elses' is required? If nerves, is it just nerves? A centralised nervous system? A brain? How much brain?

And so on.

Or take a developing foetus. We know that adult humans generally perceive pain rather accurately and acutely. But can a single fertilised cell feel pain? A blastula? At what point can it perceive pain? And is pain a binary thing, you eiother feel it or you don't, or is pain perception a gradient?

How about something with a 'brain-like blister' at the anterior of the nerve cord -- a lancelet?

Here's another thought. Does anyone know... when someone's under a general anaesthetic for an operation, do their nerves still fire off in the region being operated on? Do you need to be conscious in order to perceive pain?

If so, presumably pain perception as we humans understand it -- feeling pain rather than just responding to it -- is tied up with consciousness.

So we'd need to work out where on the tree of life -- after what node on our organismal cladogram -- consciousness evolved... Humans? Primates? Mammals? Vertebrates? Deuterostomes? Metazoans? Eukaryotes? DNA?

I ask all those questions in all seriousness. But pending answers, it strikes me that consciousness is involved. And that consciousness isn't a digital, binary condition... and is involved with brains. Can a lettuce feel pain? If not, what can, and to what extent?

That's my point, RAFH. Even amoebas act as if they're in pain, trying to get away from something damaging. It's easy for us, who are so acutely aware of what pain's like, to project "it's in pain" onto things that are not in pain in any meaningful sense, but are just reacting in sensibly evolved ways. We're so good at projecting mental states onto other things... perhaps we get false positives from, eg, a writhing earthworm.

And if with an earthworm, what else? If you kick a dog, does it yelp because it's in pain, or just because its relevant nerves fire off and cause it to react in ways that, say, bring assistance from others in the pack (or other humans)?

Strikes me that there's likely to be a gradient of consciousness... and so a gradient of pain perception ability. How rapidly it tapers off down our phylogeny is an interesting -- and probably impossible to answer -- question.

[Ray Moscow]

Yep, I agree with Oolon's approach here.

Or at least I certainly hope that the countless trillions of animals that are dying constantly aren't suffering as much as a human being would in similar circumstances.

[premjan]

I think you could look at the neural response to various stimuli to tell whether it differentiates something called pain in an analogous manner to what we do. If it has a consistent signal (eletrical alarm) for pain then it likely has some sensation of pain. Maybe not as finely graduated as our own but it is likely there.

[Sodong]

Here's another thought. Does anyone know... when someone's under a general anaesthetic for an operation, do their nerves still fire off in the region being operated on? Do you need to be conscious in order to perceive pain?There are different levels or stages of anaesthesia. Surgery is usually performed at stage 3 where normal involuntary reflexes cease to function. Stage 4 is a critical, near death stage. How well the central nervous system is depressed depends on the agent of anaesthesia. There are all kinds of them depending on the application and sometimes the "anaesthetic" is a combination of drugs where one is typically used to depress CNS function and the other is used as an analgesic. So, when you are unconscious (in stage 3 anaesthesia) you are feeling no pain and are probably incapable of feeling pain.