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Hermit Crab Molting


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Hermit crabs, like all crustaceans and many insects and other creatures, have their skeleton on their outside rather than their inside. When they grow, they need to shed the old outside skin so they can get bigger. Molting is a complicated process and sometimes stressful or even deadly. Hermit crabs typically burrow underground to complete their molt.

There are a lot of pre-molt behaviors to be on the lookout for. The hermit will increase its intake of food and water and may even spend a lot of time submerged in the water dish. Molting can take a few days for smaller crabs and a few months for large ones.

Here is a picture of my Coenobita rugosus, Monster. This is his typical coloration. (Depending on hermit crab species and food intake, they can be many different colors and some crabs may even be multicolored, such as Monster).


Occasionally, and for unknown reasons, hermit crabs sometimes molt on the surface, causing much panic to hermit crab owners. When the crabs shed their hard outer layer, their soft skin is exposed and they are very vulnerable to predation by other animals, including even their own kind. In this instance, I noticed that Monster had surface molted, so I carefully placed him in an isolation tank (within the main tank) so he could safely complete his molt.

Hermit crabs need to eat their old, shed exoskeleton to get some of the nutrients they have lost. For this reason, do not discard old exoskeleton pieces. They are an important part of the molting process.

If you look closely in these pictures, you'll see that Monster is lighter colored and almost translucent. He is actually eating his old exoskeleton, visible in the lower right hand corner of the tank. After about a week, his new soft skin hardened into his new exoskeleton and he rejoined his friends in the main tank.



Hopefully this can be of some help to hermit crab owners.

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Thanks Jenny! I remember parts of this from when I was younger but it helps to have a refresher course. I rememeber the first time my crab did this when I was little, I found the shedded exoskeleton and thought my crab was dead. I just assumed he had crawled out and died. I cried sooo hard and I called my best friend who had been there when I bought him, and had hermit crabs herself. She immediatly said "WHAT DID YOU DO WITH THE SHELL?! HAVE YOU LOOKED INSIDE?!" and I thought "huh?" and I said "nope it's still in there why?" and she said "look inside of it". I couldn't believe it when I saw that the crab was inside, light colored like you said. I was soo happy. It really felt like my pet had "come back from the dead". I cried for about 5 hours, before calling her, so all that time I thought he was gone..

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