Do Snail Shells Grow? [Full Guide]

how do snails make their shells

There is some confusion surrounding snails and their shells. How do snail shells grow? Do we have to buy them for them? Or do they make their own? When we purchase hermit crabs for pets, we have to purchase shells for them as well. Baby hermit crabs grow quickly and if they don’t have a large enough shell to move into, they can die.

Do Snail Shells Grow?

Some people think that snails are the same way, but actually, hermit crabs get their shells from snails. If a hermit crab can’t find an empty shell that suites their size, they will attack and kill snails to steal their shell. In an aquarium setting, many people purchase spare shells for their pet hermit crabs to prevent this.

Because of this, many people think they need to do the same for their snails, but they don’t. Snails are born with their shells, and they grow with them as they age. Below, you will find our full guide to answer do snails grow shells and how do snails get shells?

What Are Snails?

Snails are part of the phylum Mollusca, an invertebrate with a soft, unsegmented body. More specifically, they are part of the class Gastropoda, a group of mollusks that also contains slugs and whelks.

Snails are one of the oldest species in the world, with their ancestors dating back to the Cambrian period 500 million years ago.

They are also one of the largest groups of species with the most diversity. Over 40,000 kinds of snails are known, and they can be found all over the world from the cold mountains to the ocean depths.

What really sets snails apart from slugs are the shells that they carry around on their backs. Shells are arguably the most important part of a snail because it keeps them protected, and they can’t live without them.

So how do snails make their shells? We’ll cover that here.

Why Do Snails Have Shells?

The reason that snails have shells is quite simple: it keeps them safe. If they are attacked by a predator, the snail can curl into it’s shell, shut its operculum, and hide until the danger has passed.

Being able to hide inside their shells like this also prevents snails from drying up if they find themselves outside of water for too long. Similarly for terrestrial snails, it can prevent them from drowning if they find themselves in a large body of water.

Besides these two important reasons, the shell also acts as a storage area for calcium which they need to keep their shell healthy. It also gives their muscles a place to attach themselves. A snail’s foot is filled with strong muscles that helps them crawl around.

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Do All Snails Have Shells?

Every kind of snail has a shell. The shell is what makes them a snail and sets them apart from slugs and other mollusks. The shell is physically attached to their body and is a part of them. Without it, they will die.

Do Baby Snails Have Shells?

Baby snails all have shells, albeit small and weaker ones. The shell-growing process begins when a snail is in is gestation period, so there is never a time in a snail’s life that they are without a shell.

How Do Snails Get Their Shells?

Now that we know that all snails have shells, we need to know how they get them. Do snail shells grow? Do snails make their own shells? Do snail shells heal? Yes, yes, and yes!

Unlike a hermit crab who must hunt and steal for its shell, a snail creates it own shell.

Are Snails Born With Shells?

Let’s answer how do snail shells form.

The Protoconch

Shells begin to form inside the egg while the snail is in the gestation period. Therefore, baby snails are born with shells. They keep those same shells their whole lives, and the protective covering will grow along with them.

Before it hatches, the shell begins to form into a “protoconch”. The protoconch is the first variation of the snail’s shell, but it is not fully formed and is weak.

Calcium-Rich Foods

When the snail hatches, it immediately seeks out foods high in calcium and begins to feast. This calcium-rich diet in the early moments of a snail’s life is important in ensuring that their shells become strong and well-developed.

The eggs that the snails hatch from are rich in calcium, so the newly-hatched snails will immediately devour their first home before moving on to something else.

Although when they first hatch is the most important time for snails to load up on calcium, they will need to eat calcium-rich foods throughout the duration of their lives. Calcium is incredibly important to the health of shells, and without it, they will begin to break down and disintagrate.

Without its shell, a snail cannot survive, so it will want to prevent any breakdown of their shell by eating.

Some of a snail’s favorite calcium-rich foods include greens like spinach, kale, and broccoli.

When veggies are in short supply, snails can make do with finding calcium in soil or limestone which they will scrape with their sharp radula.

How Are Snail Shells Made?

Now we know that snails grow their own shells, but how does a snail shell grow?

The Mantle

Snails have a very important organ called a “mantle”. It’s sole purpose is to use calcium carbonate to create shells. To start this shell-making process, the mantle creates an electrical current that pushes calcium ions into the spaces they need to be.

The formation of the shell begins with the protoconch which has a small opening from which the new calcium carbonate will emerge. The mantle produces the calcium carbonate and pushes it up through the opening.

As it exits the opening, the calcium carbonate will start to harden. As more calcium carbonate is pushed through the opening and hardens, the older material will be pushed further out onto the snail’s body. This continuation of hard calcium carbonate production is what eventually forms the shell.


As anyone who has ever seen a snail knows, their shells are not perfectly round, but are spiraled. To achieve this, while the shell is being developed, it will spiral around the protoconch, producing the well-known snail spiral.

As the shell spirals, the protoconch will eventually reach the “top” of the shell, becoming the “tip” of the entire shell. Some species keep this protoconch at the tip of their shell forever, while some species lose it.

Similar to how most humans are right-handed, most snail shells will coil to the right. However, some species do have shells that will coil to the left.

What Are The Different Types Of Snail Shells?

There are three main groups of snail shells based on shape:

  • Oblong: where the height is far greater than the width
  • Depressed: where the width is far greater than the height
  • Globose/Concial: where the width and height are the same

Within these three basic shapes, the shapes of shells are broken down further:

  • Regular spiral (this shape is broken down further into many different forms. Some of these include the cone shape and the bubble shape)
  • Irregular spiral
  • Boat-shaped
  • Conical (limpet)
  • Biconic (looks like two conical shells touching bases)
  • Shield-shaped
  • Tubular
  • Pear-shaped

Do Snail Shells Grow With Them?

Do snails grow out of their shells? They don’t! Snails grow with their shells.

Growth begins in the gestation stage while the snail is still inside its egg, and it is born with it. As long as the snail grows, the shell will grow with it. Unlike hermit crabs, snails never need to worry about outgrowing their shells.

Can Snails Regrow Their Shells?

Unfortunately, snails cannot fully regrow their shells. This means that if their shell becomes so severely damaged that it cannot repair itself, the snail will eventually die.

Can Snails Repair Their Shells?

It is possible for snails to repair their shells, and they will do so using calcium and protein the same as they do when their shell first develops.

Shells: Turtles VS Snails

Although we refer to them as shells, what turtles really have are modified bones. These usually include their vertebrae, ribs, and pelvic bones that have been fused together. The “shell” is just a hard plate attached to this modified bone system to keep it protected.

When a turtle’s shell is cracked, they will likely bleed and feel pain because they’re filled with blood vessels and nerves. This is where snails are different.

Snails shells are just that — shells. Although they are attached to the snail, they are not a modified skeleton and they don’t contain blood vessels or bones.

Unlike a turtle who uses cells to fix their shell’s damage, snails use calcium and protein secretions to repair the damaged or eroded area.

So, snail shells aren’t like turtle shells, so what are snail shells made of?

What Snail Shells are Made Of

A snail’s shell contains multiple layers of materials:

  • At the base is a material called nacre, otherwise known as mother-of-pearl
  • Above that layer is hard calcium
  • Above that is the periostracum: the outer layer which is thin and made of organic material

Can A Snail Grow A New Shell?

So, snails are unable to regrow a severely damaged shell, but can snails grow new shells?

Just as a snail cannot regrow a severely damaged shell, it cannot grow a brand new shell either. If a snail is completely ripped from its shell, or its shell has degraded to near non-existence, the snail will die.

The shells on a snail are attached to their skin, so if they are injured so severely that they find themselves without a shell or with most of their shell gone, they cannot survive.

If you are wondering if snails can change shells, read our guide that answers that here.


Snail shells are made primarily from calcium carbonate and protein and are with the snail from birth. Snails begin to develop their shells while they are still inside their eggs and are born with a soft, early form of their shell.

As the snail grows, so does the shell, and it continues to grow as long as the snail does. As long as the snail eats plenty of calcium throughout its lifetime, the shell becomes harder and healthier, perfectly protecting the creature within.

A shell not only protects a snail, it is part of them.

Want to learn more about snails? Learn whether they change shells here, and whether they can leave their shells here. You can find out whether they need water here. You can also read how they breath here and find all our snail guides here.

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