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Do crabs get itches? And how do they scratch?
Question Date: 2018-06-26
Answer 1:

I am not a biologist, I do not know the answer for sure. But this is such an interesting question that I'd like to give a guess of the answer. First we can think about why do we get itchy, or, how does itchy feeling help animals in evolution. I think the main reason some animals (mammals for sure) get itchy is that it is an alert of skin infection, or parasites. When we get itchy we know something is wrong with our skin. But, crabs do not have skin, they have exoskeleton (their shell). My guess is that they do not have problems such as skin infection like the mammals, so itchy feeling does not seem useful for them.

Answer 2:

Great question! Have you ever noticed when you feel itchy? For me, it's usually when I roll around in grass, or if I accidentally touch a plant that makes me itchy, or if I have chicken pox. The reason you and I usually get itchy is because our skin is unhappy because of something we touched outside or sometimes because something is going on under the surface of our skin (like the virus chicken pox).

Most mammals feel itchy for similar reasons! Mammals are animals like cows, horses, pigs, dogs, and cats, which I'm sure you have probably seen itching themselves before. When you think about it, human skin and animal skin is actually kind of similar--it's soft, it can move around a bit, and it turns out it is sensitive to a lot of things outside.

Crab skin, on the other hand isn't really a skin at all. While you and I have skin on the outside and a skeleton on the inside, a crab wears it's hard skeleton on the outside to protect itself...like a knight in shining armor! Because of this, their skin isn't as sensitive as ours, and though they can feel pain... no one has actually tested to see if they get itchy. Maybe next time you see one, give it a scratch.. but stay away from the claws! Thanks for your question.

Answer 3:

Not in the sense that you do. Itches are responses to irritations that may be related to parasites, and scratching them might remove the parasites. Crabs get different kinds of parasites, and scratching wouldn't ever benefit them, so they don't have the instinct to do it.

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