Virtually all animals, even crabs are able to feel pain. In fact, Not only do crabs feel pain, they are also able to retain memory of it. Both pain and stress are also key survival mechanisms for the crab. There have been experiments where hermit crabs have been electrically shocked and then provided with vacant shells afterwards. In which case they were all found to abandon their old shells and enter new ones, exhibiting stress related behaviors such as grooming of the abdomen or rapping of the abdomen against the empty shell.
Grooming for a crab can also be used as a protective motor reaction viewed as a sign of pain. Crabs are also equipped with a central nervous system and receptors that help them learn to avoid negative stimulus after experiencing such. Like humans if they are hurt they will limp or rub the appendages that are in pain. Studies have also shown physiological changes that occur within the crustacean including the release of adrenal like hormones that occur when pain or stress is suspected in the creature much similar to that of a human. Unfortunately for crustaceans such as the crab, they often become food for humans and sometimes are even boiled alive. In which case, they would feel pain! Perhaps this is something most of society should begin to consider.
Harry says
You say that all animals feel pain. This is almost certainly true but the “experience” of pain is something totally different. Animals from Humans right down to single celled animals will display an avoidance reaction to external stimuli. However it is very likely that in the vast majority of animals this feeling of pain is a good thing in that it is one of the primary motivators of the survival instinct. Without it the species mix of the ecosystem would be very different, if, that is life survived at all.
It is only as we move higher up the line of evolution to the mammals, and in particular higher primates, that the physical “feeling” of pain is likely to evolve into an emotional “sensation” of pain. Pain is no longer a feeling that is an automatic inducement to move away from the source of pain, (and not to go back), but it becomes an emotional “I don’t want to feel that again, it hurts ME, get ME away from it.” In other words, the experience of pain becomes closely linked to a strong sense of self awareness and self identity.
You make a mistake which happens repeatedly in articles and papers , when you say that “crabs release adrenal like hormones similar to that of humans”. This implies that crabs have copied humans, and that they therefore share other human traits and characteristics as well. This is obviously not so.
The reality is the reverse. Humans release adrenal like hormones similar to that of crabs. This is not surprising since mammals and latterly human evolved a long time after crabs. It is highly likely that we will still display many of the early evolutionary characteristics of animals that evolved many millions, even billions of years ago, but this does not mean we are stuck with them.
However evolution has moved on and, over tens of millions of years, has produced some very highly developed mammals such as the hominids and higher apes. A humans nervous system contains approaching 100 billion neurons compared to a lobster’s tiny 100,000. We have a highly developed brain cortex and limbic system, both of which are linked to our sensation, interpretation and experience of pain. Compare this to a crab’s very simple giant ganglia dotted along its nerve cord that simply receive a pain message and send back a response in a way very similar to our own autonomic nervous system which gives us automatic, unconscious response to a stimulus.
So, yes, almost certainly crabs do feel pain, but it is extremely unlikely that they have any appreciation of pain, or even “know” that they are feeling it.
And in response to your final paragraph commenting on crabs being boiled alive, in which case they “would feel pain”. This is fact is highly unlikely. Research shows that a crab’s neural muscle pathways catastrophically shut down at temperatures above 35 degrees C. This, to us is mild tepid water. So dropping a crab into boiling water would almost certainly cause an almost instantaneous cessation of any sensation at all.
I don’t think society does need to consider the implications of pain in crabs. It is easy to equate everything we see in Nature, especially regarding pain and suffering as an equal to our own ability to experience pain and suffering. But people seem to forget that we came from nature, not the other way round. We have evolved enormously in the last few million years, taking the basic building blocks of nervous system precursors, and evolving them into a highly sophisticated system resulting in a high sense of self , and the consequential experience of pain and personal suffering. We should not be reflecting this backwards into earlier evolved life forms.