If you own a Hermit Crab in your aquarium, you will see them without their shell once in a while. However, there is no need for you to get panicked about it.

It is absolutely okay for a Hermit Crab to be seen without a shell. It is a natural phenomenon that may be seen a few times throughout their lifetime.

The main problem arises when people get confused and don’t understand what is actually going on with them. Moreover, many people get scared because the Hermit Crab without its shell looks like something out of an alien movie.

Hermit Crab without shell

Hermit Crab without shell
Hermit Crab without shell

As you may know, Hermit Crabs do not possess or make their shells naturally (reference, paragraph 1). Rather, they rely on the shells of other aquatic animals. Furthermore, their inner body doesn’t have the hard exoskeleton protection like other crabs, but rather it is soft and vulnerable.

Consequently, they feel the need to protect their squishy bodies with something. So, after years of evolution, they have adapted to using a shell or anything that resembles a shell, which provides enough protection to keep their bodies safe from the outside world.

They mostly use the shells of dead snails or abandoned shells of other Hermit Crabs. Although there are no preferences for what kind of shell they want, they just use the ones that fit them.

Apart from this, you may also see them use other inanimate objects as their protection, such as glass jars, metal cans, plastic bottles, cups, etc., which I must say, is quite fascinating.

Generally, common land Hermit Crabs change their shell at regular intervals, but some species are special in regards to this-

In the wild, Purple Pincher or Caribbean Hermit Crabs can change their shell very often, almost every day. Whereas, the Ecuadorian Hermit Crabs change their shells every so often because they like to modify their existing shell to fit their changing size.

Reasons- Why do Hermit Crabs move out of their shells?

There are a few reasons why Hermit Crabs leave their shells. A few common ones are described below-

  • A general replacement

Sometimes, the Hermit Crab may see something that they think will fit them better than the existing one. At that time, they will leave their shell and move into the new shell. But this process takes place on the spot, in a very short interval.

  • They have grown in size (Molting)

If you already have a Hermit Crab, then you probably know that they live for a long time, approximately 15 to 20 years. As a result, they grow in size but their shell does not.

They have grown in size (Molting)

So, they need to get rid of it and get a bigger one. It is just like us humans, buying a new set of clothes as we grow in size.

This is the time when they are ready to molt from their exoskeleton. A few indicators can assist you in determining when it is about to shed.

  • They have been eating lots for a week, followed by an immediate halt.
  • They tend to move slowly and get lazy when they are about to shed.
  • Their skin will become paler by the day.
  • Your Hermit Crab will try to find a hiding spot and stay there most of the time.
  • The position of their eyes will change and they will point in an outwards direction.
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If you are able to perceive these signs, then you will know it’s that time of the year when they are about to shed and get a hold of a new shell. This will become their new home till the next molt.

  • Invasion inside their shell
Invasion inside their shell
Image Source -Inhabitat.com

Another reason could be that something foreign has wedged itself inside the shell. It could be a parasite like a mite, a fungal or bacterial infection, or even small gravel particles. This can bother the crab to a limit where they are forced to leave and find a new home.

This happens the most when proper care is not taken. Your crab can benefit from clean water and a good diet to help prevent avoidable infections.

  • They could be sick

Your Hermit Crab may be suffering from some kind of disease or sickness. It is not uncommon for them to encounter mortal infections. One of them is Shell Rot, which creates holes in their bodies leading to death.

They could be sick
They could be sick

In these situations, Hermit Crabs may even leave their shell as they feel uncomfortable inside. Also, temperatures inside the shell are warmer than outside, which provides a suitable place for bacteria to multiply exponentially.

  • Microplastic Pollution
Microplastic Pollution

You may have seen plastic items scattered all over the beaches. This is an example of microplastic pollution, which affects the shell selection of the crab (reference). Sometimes, a crab may mistake a plastic item as a replacement but ends up abandoning it after a while. This makes it difficult to choose a proper home for protection.

  • Fighting for shell (in nature)

Sometimes, if a Hermit Crab locates a shell that will suit them better. But when it is occupied by another of its species, they will tend to fight.

Fighting for shell
Hermit crab fighting for shell

Usually, the stronger one tries to evict the weaker one from their shell by fighting, and the other one is forced to leave and find a new one (reference).

  • External Parameters

When a season change occurs, the temperature in their shell also changes. Sometimes, it may be too warm or too cold inside.

In that case, they will have to find a shell for themselves that will insulate their bodies from the changing temperature.

Hermit Crab’s appearance without the shell?

A Hermit crab looks very different and looks nothing like a crab. Unlike its outer body, which is covered by a hard, chitinous-calcium carbonate compound exoskeleton, the inner half is exactly the opposite.

It does not contain any hard shell, but rather it looks like a muscular appendage resembling a shrimp or a thick worm. It is naturally curved and is much smaller compared to the rest of the body.

The curved posture of the soft inner body helps the crab to grab hold of the inner part of the shell. Additionally, it is very flexible and it acts as a hook to keep the body affixed to the shell.

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The color of the inner part is also different from the rest. It is a lot paler compared to their outer bodies. Along with that, it also consists of tiny hair-like structures, but it is hardly noticeable.

Help your Hermit Crab get a new home

Now that your Hermit Crab has abandoned their old shell, they need your help to find another one.

In other words, they cannot simply scour around the area looking for a discarded shell as they do in the wild. You have to provide them with a new one as they won’t be able to survive for long with their exposed and vulnerable bodies.

But there are a few things you have to do so that your crab can comfortably move into a new shell without experiencing too much stress.

Carry out an inspection

A good diagnosis will help you understand the situation. We have already discussed the reasons for leaving their shell behind. Before you do anything, you should first check if your crab is molting.

You should also check for diseases and other symptoms if it is not molting. If a brief visual inspection doesn’t cut it, you should probably take it to a professional to have it examined.

Isolating your crab

If molting or sickness is the case, you should isolate the crab as soon as possible. You can either transfer it to a different enclosure or put a barricade around the existing one, so it feels less uncomfortable.

To isolate them in their own enclosure, you can use waste materials such as plastic bottles or large jars. Make sure they have access to the substrate if they ever decide to burrow inside. Hermit crabs do that when they feel vulnerable, especially if other crabs are in their vicinity.

If the crab takes too much time with molting, provide them with food to help it gain strength to shed its exoskeleton. After that, it is mostly a matter of a waiting game.

However, if you decide to put it in a different tank, you may have to first sterilize your tank walls with a strong disinfectant to make it safe. And try to maintain a dark environment during the isolation; it makes them feel more secure.

Provide them with a new shell

This is very important as they cannot wander off out in the open looking for a new shell. Try to provide them with a new shell as soon as you see them coming out of the older one, so they don’t stay exposed for long.

Now, just handing them a new shell isn’t enough. You need to follow some crucial protocols to ensure your precious crab doesn’t face any difficulties later on.

Choose a suitable replacement

You need to make sure the new shell is hard and not easily breakable. Also, it should not contain any holes or cavities. Natural shells are the best option, but you can also buy artificial shells for them.

Some shops sell decorative high-quality plastic or acetate shells for Hermit Crabs but are quite expensive. Some people like to put various decorations on natural shells and sell them at an increased price.

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Furthermore, you should try to provide a few options for your crab. It will choose the best one based on the space and weight of the shell.

Disinfect the shell

It is very important that the shell which you choose must be properly disinfected. You may use a povidone-iodine solution to wash the shell. Additionally, you can also boil it if you suspect anything is still living inside it.

Patience

After doing all this, the only thing you can do is be patient. Give your Hermit Crab enough time to move into the new shell. The time it takes to move in cannot be predicted. It can take a few hours to a day or two.

If your crab is facing difficulty fitting inside, you can change the existing and provide it with better options or help it fit in if you think by nudging it slightly. Sometimes the shell can be a bit heavy for them, so a little help from you is greatly appreciated.

Frequently Asked Questions

Are glass shells bad for Hermit Crabs?

Customized glass shells are sold in shops, but they have a much higher price tag. Even though they are strong and give a very unusual look to the crabs, they have a major disadvantage. These glass shells are either transparent or translucent, so it allows the sun’s rays to penetrate all the way through and increase the temperature inside. This is bad for the crab as the inner body is soft and an increase in temperature will make them abandon their shell.

Will a hermit crab live/die without a shell?

The inner body of a Hermit Crab is very susceptible to catching a disease or getting injured, as discussed above. So, if it stays out of its shell for a long time, it can face problems where death might be a consequence of it. The shell protects it from external elements, so an unprotected hermit is almost as good as dead if left like that for long.

Do Hermit Crabs exchange shells?

Yes, they do exchange shells with each other if they need to. It is an amazing sight if you are lucky enough to catch them doing that. It mostly happens in the wild, where you need a lot of Hermit crabs of various sizes. They gather around briefly, which is then followed by a line formation. They stand in descending (big to small) order from the front. Then, once the line is made, each crab gets out of its shell and moves into another bigger shell right in front of it. This happens very quickly and is a rare phenomenon.

Conclusion

So now, whenever you see your pet Hermit Crab escape its shell, try to keep your cool and assess the situation first. They will do it one day, so keep yourself prepared and don’t let the fear get the best of you.

Just follow the basic precautions and let the crab do its thing. If there is any sickness involved, try consulting an expert to get a better view of the situation. 

About the Author

Victoria Lamb

Victoria is a freshwater aquatics specialist, fish keeper, and amphibian enthusiast. She has had more than 6 years of experience caring for aquariums and keeping several fish species, and her home boasts of 3 aquariums and a garden pond. Her goal is to educate fish owners on raising healthy and happy aquatic pets.

Career Highlights:

  • Has worked with several aquarium manufacturers as a consultant
  • Organized and hosted workshops on freshwater fish keeping at retail stores, educational facilities, and libraries
  • Released content for the amphibian community through her writings

Educational Highlights:

Bachelor of Science in Animal Behavior and Welfare

  • University of Lincoln, Lincoln, UK (2014-2018)

Writing Experience

Victoria has done ghostwriting for many aquarium and pet websites in the past. She has also worked for Canada's largest natural health magazine- ALIVE, with 300,000 monthly circulations as a freelancer. She had six published articles on animal behavior and welfare during her graduation for her thesis.

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