Where do Hermit Crab Shells Come From?


I was recently buying some shells for my hermit crabs. While gazing at their spiral shiny shells through my computer screen, I started to wonder. Where do these shells come from?

I was one Google Search away from my answer, so I did some research.

So, where do hermit crab shells come from? Hermit crabs cannot develop their own shells. In order to protect themselves, they steal leftover shells from deceased gastropods (snails and slugs).

Let’s dive a bit deeper into their act of “borrowing” snail homes, how they’re formed, and explain the importance of their shell.s

“Borrowing” Snail Homes

Believe it or not, your little hermit crabs may not be walking around in borrowed homes. In fact, not a single one of your crabs ever made the shell they’re scurrying around in.

As mentioned before, hermit crabs claim the shells of deceased snails and slugs, sometimes. Most of the time this is not the case. Hermit crabs have been known to kill snails if they see one with a shell they desire.

Sometimes it isn’t snails who are unlucky, sometimes its other hermit crabs in their colony! Hermit crabs have also been known to gang up on a crab with a prized shell to claim it as theirs.

With these shells, they stay protected from predators and grow. Over time and a few molting cases later, they’ll be too big for their shell. When that time comes, they go house hunting.

Once they find a shell that meets their needs, they simply dump their old shell for the newest model.

That’s right. Your hermit crab is basically a squatter who can’t seem to stay in one place. They find an empty “home” and walk around in it until they get too big and find a larger one.

This is why hermit owners like myself have to buy a variety of shell sizes for their hermit crabs. They can’t form them on their own, so they need plenty of choices to live comfortably and feel safe.

Shell Lines

When shells become scarce, sometimes hermit crabs settle their differences and help each other out.

Shell lines, also known as a vacancy chain, are an easy fix to their common problem. It’s similar to hand-me-downs most children with older siblings are so familiar with.

Say, for example, that the largest hermit crab in the colony just found a new, large shell. The second-largest will line up and take its old shell, then leave its shell for the third-largest and so on.

This line of hermit crabs exchanging their old mobile homes goes down to the smallest crabs in the community. It’s a simple way to avoid shell fights and spend more time looking for food and avoiding predators.

The only time shell lines would not work is if there were more than one hermit crab in the group that’s in need of the same shell.

How Do Hermit Crab Shells Form?

The creation of mollusk shells is an intricate process with many phases and small details. There’s an entire field of study dedicated to the study of mollusk shells called Conchology.

Scientists researching conchology determined how mollusk shells are formed.

Snails, slugs, and other gastropods create their shells by taking in salts and chemicals from the water and turn it into calcium carbonate. This substance is then secreted from the mantle and hardens on the outside of their shell. Soon after, the substrate hardens leaving behind a beautiful, protective shell.

These shells can grow into variously different shapes, depending on the shape of the gastropod. Shells grow in layers extruding outwards from the snail or slug, creating beautiful shapes.

Your hermit crab shells also come in a variety of different natural colors. These depend on the creature’s diet and environment. For example, if the snail lived in a coral reef and its daily diet was a healthy mix of brightly colored corals, its shell would show a similar color. That’s why we find such beautiful shells in more tropical waters.

The Importance of a Shell

Hermit crabs are crustaceans, famous for their segmented bodies and exoskeletons. You’ll see strong and sturdy exoskeletons on other crustaceans such as Dungeness Crabs, Blue Crabs, or lobsters.

Hermit crabs have exoskeletons like other crabs, but they aren’t true crabs. In fact, their exoskeletons are soft and puny. This leads them vulnerable to predators.

They don’t have a way of defense unless you count their laughably small claw, which makes a sturdy, safe shell very important.

Whenever faced with danger, a hermit crab can just tuck away in its shell. It’s very effective to protect themselves from predators or other threats.

Related Questions

Do Hermit Crabs Have Shells When They’re Born?

Hermit crabs are not born with protective shells. One of the first things they have to do after being born is to find a small shell from a deceased gastropod for protection.

Can a Hermit Crab Live Without a Shell?

Hermit crabs can live for several weeks without a shell if properly cared for. They are, however, are easily stressed and exposed without one. If your hermit crab evades its shell, present it with plenty of food, water, and extra shells to choose from.

Taylor

When I bought my two hermit crabs on the boardwalk over three years ago, I had no idea I'd have them for years to come. I created this website to teach others what I've learned about caring for hermit crabs.

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