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Jerad81

Do crabs lose thei arms/claws naturally?

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Jerad81

Yes, I'm REALLY hoping for a miracle even though I believe I already know the answer.

I recently bought 4 porcelain crabs that arrived perfectly healthy and were added to my tank yesterday. One of them has been MIA ever since. I assumed it was just hiding to help deal with the stress of a new home. Earlier today I found two crab claws with the arms still attached and appear to have been ripped out of the crab's body. The body is nowhere to be found though.

I found the other three crabs and they all appear perfectly happy and have both arms and claws still attached. I bought 4 of them because they are supposed to do well in groups. I also have a decorator crab, 3 pajama cardinals, a  banded circus goby and a cleaner shrimp. 

Unless one of the other porcelain crabs or the decorator crab decided to have  a moment of violence, there's nothing in my tank that would or could rip it's arms out.

Now I feel like I have to ask. Is it possible for a crab to "shed" their arms/claws and regrow new ones or do I have a real murder mystery on my hands?

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billygoat

One thing I have noticed about porcelain crabs is that under certain conditions they seem to spontaneously drop their limbs. I have even observed specimens that were separated from all other animals in their environment (isolated in a small jar) do this. I have a feeling that this behavior somehow related to either extreme stress or a lack of available food; perhaps the animal realizes it is not getting proper nutrition and opts to jettison one or more "optional" parts of its body to keep the rest going? Whatever the cause, it's definitely a thing, so don't worry too much about aggression if you see this going on.

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Jerad81

Wow, I had no idea they did that. That is great to know, thank you!! 

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king aiptasia

ive seen even true crabs if an arm has been injured to rip the whole thing off. i assume its because its less painful to rip it at a designated break point than a torn muscle etc

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mcarroll

They also molt more or less regularly and that will also generate "spare parts".  If I'm not mistaken they will also drop a claw in self-defense.

 

Molting it pretty common when inverts get into water with different chemistry.   Water changes seem to spur molting sometimes too.

 

FYI though, other than the filter-feeding porcelain crabs, you cannot trust a crab!  Keep your eye on that decorator!

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debbeach13
3 hours ago, mcarroll said:

Keep your eye on that decorator!

I will never have one of these again. My one and only attempt at one was a disaster. He torn up so much coral. I gave it back to the store I got it from.

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Jerad81
3 hours ago, mcarroll said:

They also molt more or less regularly and that will also generate "spare parts".  If I'm not mistaken they will also drop a claw in self-defense.

 

Molting it pretty common when inverts get into water with different chemistry.   Water changes seem to spur molting sometimes too.

 

FYI though, other than the filter-feeding porcelain crabs, you cannot trust a crab!  Keep your eye on that decorator!

 

22 minutes ago, debbeach13 said:

I will never have one of these again. My one and only attempt at one was a disaster. He torn up so much coral. I gave it back to the store I got it from.

Yeah, I've heard that about decorators from quite a few people. So far mine hasn't touched any of my coral. Not even to wear it. Although I did have aiptasia springing up all over my tank and he gobbled that all down pretty quick. He didn't even try to wear any of it either so he's been a bit of a hero at the moment. I am keeping a close eye on him though just in case. 

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