Be nice to your crabs!

[Sharkey18]

Check this out, studying hermit crabs...

 

http://www.cnn.com/2009/WORLD/europe/03/27...pain/index.html

[lanman]

Oh, lord... now we're going to have to find a way to peacefully euthanize crabs before we toss them into a pot of boiling water. While playing soft music, no doubt.

 

bob

[Jan]

Check this out, studying hermit crabs...

 

http://www.cnn.com/2009/WORLD/europe/03/27...pain/index.html

uh-oh more ammunition for PETA. Mantis shrimp owners who like to video tape feedings beware!

[Mich]

If you take into account the ratio of biotic potential to actual survivability of these animals in the wild it seems to me like there is a very high degree of death abounds, which one would assume after reading te article, coincides with an equally high degree of pain. Assuming from a fossil record perspective, that everything living on the planet right now only accounts for a minority of everything that has lived; one can infer that our time has been preceeded by eons of pain, suffering and death. It's because of this that I fail to see the rationalitiy of transeffering our own sense of existential despair into sympathy for organisms that are destined to suffer and die perpetually regardless of our involvement.

[FishyTim]

True, but was pain, suffering and death all they experienced?

 

[quote name='Mich

[extreme_tooth_decay]

It just gets sillier and sillier....I wonder how long it will be before it is discovered that viruses and bacteria have some kind of reflex to harmful stimuli which could be interpreted as pain...which they try to avoid in the future...perhaps it has already been discovered...I wonder if these folks use antibiotics, vaccines, hand soap, etc.

 

 

 

uh-oh more ammunition for PETA. Mantis shrimp owners who like to video tape feedings beware!

 

 

Shakin in my boots over here! The champ has been fighting some pretty amusing battles recently. He is still the champ!

 

 

mmm...did someone say crab?

 

Edited March 30, 2009 by extreme_tooth_decay

[FishyTim]

That's an awesome picture!

 

It just gets sillier and sillier....I wonder how long it will be before it is discovered that viruses and bacteria have some kind of reflex to harmful stimuli which could be interpreted as pain...which they try to avoid in the future...perhaps it has already been discovered...I wonder if these folks use antibiotics, vaccines, hand soap, etc.

 

 

 

 

 

 

Shakin in my boots over here! The champ has been fighting some pretty amusing battles recently. He is still the champ!

 

 

mmm...did someone say crab?

 

[OUsnakebyte]

I was intrigued (mostly for possible work implications), so I sought out the reference and downloaded the paper, though I have yet to read it.

 

I can't upload the pdf file, since it is 160kb, and I am only allowed 60kb. So, I copied/pasted the paper if anyone wants to read it.

 

Cheers

Mike

 

 

Abstract

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.

2009 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd.

 

Introduction

Nociception is the ability to detect a noxious, potentially tissuedamaging, stimulus and respond to it (Sneddon 2004) whereas pain is the associated unpleasant, emotional interpretation or feeling associated with that perception (Broom 2007). There can be little doubt that decapod crustaceans have a nociceptive ability as they readily detect and withdraw from noxious stimuli (Kawai et al. 2004; Barr et al. 2008). However, there is a debate whether they are able to experience the emotional component (Sherwin 2001;Broom 2007; Barr et al. 2008), driven, in part, by a concern for the implications for the welfare of these animals, which are widely used in fishing, aquaculture and the general food industry. Since

animals cannot be asked directly, indirect methods and argument by analogy may be applied in an attempt to answer this question (Sherwin 2001). Thus a species is considered to have the potential to feel pain if it fulfils certain criteria, such as: having a suitable nervous system; displaying protective motor reactions; showing trade-offs between stimulus avoidance and other motivational requirements; having opioid receptors; reduction of responses to noxious stimuli by analgesics and local anaesthetics; having high cognitive abilities; showing avoidance learning (Elwood et al., in press). We briefly consider these points with respect to decapods. The neocortex has a central role in human pain and it has been argued that any species lacking this structure will be incapable of that feeling (Rose 2002). However, it is possible that different structures may be involved in the pain experience of other animals, in the way that decapods have vision despite lacking a human visual cortex (Elwood et al., in press). Thus it is difficult to determine whether or not decapods have a suitable nervous system and we must look more to behaviour to test whether they feel pain. Prawns, Palaemon elegans, show protective motor reactions when their antennae are treated with a noxious substance (Barr et al. 2008). They specifically groom the treated antennae and rub them against the tank, showing the animals are aware of the location of the noxious stimulus. Motivational trade-offs occur in crabs, Carcinus maenas, that receive a shock in a dark shelter in that they are more likely to leave the shelter after the shock if the ambient light is low, indicating an interaction of motivational systems (S. Barr,

F. Mansoor & R.W. Elwood, unpublished data). Opioid receptors are present in decapods (Dyakonova 2001) and morphine inhibits the defensive response to an electric shock in the crab Chasmagnathus granulatus in a dose-dependent manner (Lozada et al. 1988). The cognitive abilities of hermit crabs in information gathering and decision making are impressive. They rely on the use of gastropod shells for shelter and shells of adequate size, shape and strength, but without being too heavy (Briffa & Elwood 2005), are a key resource (Elwood & Neil 1992). A hermit crab gathers information about shells by vision (Reese 1963) but this information is enhanced during approach and contact. After contact it grasps the shell with its walking legs and chelipeds and explores the exterior, moving its chelipeds over the surface, and then turns the shell so that the aperture is uppermost and begins to investigate the interior by inserting one or both chelipeds or sometimes a walking leg. It obtains detailed information as to the size, internal volume, shell species (shape) and weight during this process and assesses the overall quality relative to that of the shell it is currently occupying (Elwood & Stewart 1985; Jackson & Elwood 1989a; Elwood 1995). The crab may move into the new shell and test the inside of the shell by thrusting the abdomen back and forth. It might also investigate the interior and exterior of the original shell and even move back into it, assessing which is the better of the two (Elwood 1995). Hence these crabs demonstrate sophisticated shell investigation behaviour, remembering the information gathered at each stage of the investigation, and also remembering specific shells for

up to 40 min (Jackson & Elwood 1989b). They may also fight another crab over ownership of shells in which case information about the shells and the opponent is integrated with information about their own physiological state (Briffa & Elwood 2004). They can remember previous opponents for up to 4 days (Gherardi & Atema 2005) and it has been suggested that they may select which crabs to fight on the basis of their perception of how their current shell might suit the opponent (Hazlett 1996). Thus crabs have the ability to gather and use information from a variety of sources and to make comparisons between shells and between opponents. The main function of the unpleasant feeling of pain is that the animal will remember the circumstances that led to it and avoid those in the future (Bateson 1991; Broom 2001). Avoidance learning has been demonstrated in crayfish, Procambarus clarkii (Kawai et al. 2004), which escape into another compartment of the tank to avoid an electric shock. Additionally, connections from nociceptors to learning centres are found in decapods (Sandeman et al. 1992). Thus decapods show features that are consistent with the idea of pain.

Preliminary tests have shown that electric shock delivered to the abdomen within the shell causes hermit crabs to evacuate their shells when sufficiently severe. The object in the present study was to give some crabs shocks at just below the threshold required for the majority of crabs to evacuate whereas others were not shocked. We determined whether the quality of shell influenced the decision to evacuate and thus whether there was a trade-off between conflicting motivational demands. Crabs that retained the shell were subsequently offered a new shell and we determined whether the quality of the existing shell and the prior experience of shock influenced their subsequent responses towards that shell. Immediate

evacuation of a shell when shocked may be viewed as a simple, nociceptive reflex but here we examined whether

a noxious stimulus that is not strong enough to cause this is nevertheless remembered and used in subsequent decision making about changing shells. Thus we investigated how the motivation of the animal is altered by a previous noxious stimulus. A significant effect would demonstrate a memory of the experience, an awareness of the location of the noxious stimulus and the use of actions that are appropriate to escape from the situation after the stimulation has ceased.We thus investigated nonreflexive responses that might be consistent with the concept of pain in these crustaceans.

 

 

METHODS

Hermit crabs, Pagurus bernhardus, were collected from rock pools at the shore at Ballywalter, Co Down, Northern Ireland, U.K. (54 320000N, 5 290000W) in May and June 2008 at low tide. They were transported to Queen

Edited March 30, 2009 by OUsnakebyte

[Mich]

True, but was pain, suffering and death all they experienced?

I doubt that solely those three attributes completely define the whole of decapod existence. However, whether or not they feel joyful, nostalgic, melancholly, or resentful is more difficult to determine. What's obvious is that pain often or usually preceeds death and being able to recognize and avoid pain is likely a a helpful way to stay alive longer. So, it seems resonable for pain to be a popular trait in species that have thus far avoided extinction. Does feeding crabs to mantis shrimps irreparably damage the balance of nature on this planet, or cause undue suffering to a chosen race of God's malacostracan children who will one day rise up in vengeance to defeat the vile kingdom of man? Unlikely. I think people have misappropriated their sense of sympathy do to growing up in a society that's been overly endeared to notions of anthropomorphic animals dancing, singing, laughing and loving. The reality of nature, especially as it pertains to reef life, tends to be completely amoral as well as sort of brutal. But, for some reason a lot of people in this world think it's supposed to be something like this;

 

http://www.youtube.com/watch?v=yPpNNpzldbg...feature=related

Edited March 30, 2009 by Mich

[Hilary]

I think whether they feel pain is pretty much a no-brainer - I would imagine that most critters do to some extent. Just read the abstract - very interesting the way they went about their research. It's all about survival, baby!

[treesprite]

This sort of experiments are ignorant. We have absolutely no way of knowing whether or not the signal the animal's brains are receiving from the body's physical sensation is an unpleasnat feeling or not. The experimenters would have to explain their definition of pain as either a subjective physical sensation OR a bodily function. As an unpleasnat physical sensation, the concept of pain is not a suitable subject for experimentation on lower animal lifeforms because we can only make inferences about the animals' behaviors as if those animals experienced and processed sensations and thought processes the same way humans do. As a bodily function, for all we know the physical sensation the animals experience could be a pleasant one. For humans being tickled can make a person laugh because it is pleasant, but the physical sensation is just the body telling the brain that there is a physical irritation. How do we know the animals weren't actually feeling as if they were tickled as opposed to having an emotional mental suffereing as the result of the stimulation?

Edited April 1, 2009 by treesprite

[FishyTim]

My point was just because they will encounter pain and eventually death doesn

Edited April 1, 2009 by FishyTim

[extreme_tooth_decay]

This sort of experiments are ignorant. We have absolutely no way of knowing whether or not the signal the animal's brains are receiving from the body's physical sensation is an unpleasnat feeling or not. The experimenters would have to explain their definition of pain as either a subjective physical sensation OR a bodily function. As an unpleasnat physical sensation, the concept of pain is not a suitable subject for experimentation on lower animal lifeforms because we can only make inferences about the animals' behaviors as if those animals experienced and processed sensations and thought processes the same way humans do. As a bodily function, for all we know the physical sensation the animals experience could be a pleasant one. For humans being tickled can make a person laugh because it is pleasant, but the physical sensation is just the body telling the brain that there is a physical irritation. How do we know the animals weren't actually feeling as if they were tickled as opposed to having an emotional mental suffereing as the result of the stimulation?

 

 

That is exactly right.

 

Even the first half of the first sentence of the abstract is nonsense. My response is "uh, no it cannot". I didn't read past that.

 

tim

[Mich]

My point was just because they will encounter pain and eventually death doesn

Edited April 1, 2009 by Mich

[Sharkey18]

The study is pretty interesting, but the responses to it are even more interesting!

 

It seems pretty obvious that creatures with even a simply nervous system would have the ability to feel pain and this study shows some interesting results on that end. I don't really think there is anything in this study to get ruffled about. I mean there is no doubt that cows feel pain yet we slaughter them,not particularly humanely and eat them by the thousands, me included. There is very little threat to us as aquarists and carnivores from this information. It's just information so why the resistance to the information, especially if you didn't read it? Just because you may disagree with a premise doesn't mean the science is junk. It just means you disagree. That's what peer review is for, to put forth ideas for discussion.

 

I always laugh when people are so put out when science is able to define sensory perception in other animals. I mean could we be any more in charge of this planet? Do you really think PETA is going to get a huge following of crab rights people that are going to significantly influence our lives? I doubt it. Methinks the protests are curiously strong. Interesting.

 

Laura

[extreme_tooth_decay]

It seems pretty obvious that creatures with even a simply nervous system would have the ability to feel pain and this study shows some interesting results on that end.

 

 

Doesn't seem obvious to me at all.

 

I have a video of a crustacean tearing it's own limb off and handing it to it's attacker, then walking away at a leisurely pace, not doing anything unusual at all (or giving any appearance of being in "pain", whatever that might look like).

 

This is an act that no creature with anything that we can associate with as what we call "pain" could do.

 

As with several other "studies" of this sort I have read, the authors are making outrageous claims that simply cannot be backed up. The first sentence of the abstract is a prime example.

[Sharkey18]

I saw the video of the shrimp handing over its limb and it is fascinating! It's another piece of the puzzle that makes you wonder about the whole pain thing. However just because the shrimp did this, doesn't mean that crustaceans and decapods don't feel pain. There are plenty of other explanations that could account for the shrimp to have the ability to feel pain AND be able to rip off and hand over a limb. Like survival mechanisms designed to block pain in order to hand over a limb in exchange possible survival. I'm not saying thats what happened I'm just say ing its a possibility because we don't KNOW for sure. In fact there is plenty of evidence that this same thing DOES happen in people. Horrible injuries, including loss of limbs that do not "hurt" at the time because of the bodies amazing arsenal of survival mechanisms, both chemical and psychological.

 

They are not claiming that is it like "anything that we can associate with as what we call "pain" .

 

And just because the hermits switch shells doesn't mean they do feel pain like humans only that it meats the criteria that the authors set forth. And no one is claiming that crustacean and decapod pain is the same as human pain.

 

The authors definition of the POTENTIAL to feel pain:

 

"indirect methods and argument by analogy may be applied in an attempt to answer this question (Sherwin 2001). Thus a species is considered to have the potential to feel pain if it fulfils certain criteria, such as: having a suitable nervous system; displaying protective motor reactions; showing trade-offs between stimulus avoidance and other motivational requirements; having opioid receptors; reduction of responses to noxious stimuli by analgesics and local anaesthetics; having high cognitive abilities; showing avoidance learning (Elwood et al., in press). We briefly consider these points with respect to decapods.

 

Certainly that definition is open to discussion and they acknowledge that this is an active debate.

 

It's just more information on a subject that is not well defined. I am not convinced they proved what they claim either but I don't think it's ignorant to ask the question. Even if they did feel pain would it change anything? I doubt it.

 

Laura

[Mich]

Do you really think PETA is going to get a huge following of crab rights people that are going to significantly influence our lives?

 

Yes! It's happened. They exist!

 

Because of these people's exceptionaly tender sensibilities, the very best of extreme tooth decay's videos (absolutely great BTW) have been pulled from youtube. The controversy over the article is due to the semantic error of using the word "pain". They didn't say "adverse pysical stimulus" or the like. They named a human emotion, which could be viewd as socially irresponsible seeing as people can have a tendency to be too sensitive, and take things way too literally.

[Sharkey18]

That's too bad. Do they remove Nat Geo programs of lions bringing down gazelles? Too bad for extreme tooth decay. I enjoy watching the predator - prey interactions and don't think it's any different than feeding crickets to a lizard.

 

Laura