A-z - Animals

Are snails without shells just slugs?

Updated: December 27, 2022

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Snails and slugs – pesky cousins or identical twins (except shells)? Many people don't know much about the difference between snails and slugs, other than that they are slimy. While this is true, these animals are amazing creatures that hold a unique place in their respective ecological niches. Let's look at these two and learn: Are snails without shells just slugs?

Before we go any further, before we do anything else, it might be important to know what exactly these two creatures are!

What is a snail?

A garden snail is a snail without a shell and is just a snail plant
Snails are part of the gastropod family and are identified by their shells.

© iStock.com/Daniella Schroeder

"Snail" is a loose term for shelled gastropods. Terrestrial, freshwater, and saltwater snails, as well as at least some type of shelled gastropod, can be found in nearly every ecosystem in the world. Most of the time, the term snail refers to terrestrial snails, but can also include their aquatic counterparts, especially since snail is not a scientific term but a popular one.

Simply put, if a gastropod had a shell, most people would call it a snail. Some snails can retract completely into their shells (many aquatic snails do), but terrestrial snails generally cannot.

What are slugs?

Are snails without shells just slugs?
Slugs are gastropods that have no shell, or only a small inner shell.

© iStock.com/Ja'Crispy

Slugs belong to the same taxonomic group as snails (gastropods). There are two groups of sea cucumbers, sea cucumbers and land cucumbers. Nudibranchs have the smallest or inner shells and live only in the ocean. However, the slugs most people are familiar with are terrestrial. They are completely soft-bodied, with no inner or outer shell.

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Slugs have evolved in different ways, and many of them share no common evolutionary ancestor. This form of convergent evolution (when two species evolve similar traits without a common ancestor) gave rise to distinct mollusc gastropods, which we call "slugs," although many gastropods differ from each other. There is no evolutionary relationship between them. Sea cucumbers and land cucumbers are good examples because they have a name but not an ancestor.

Are snails the same as slugs?

Are snails without shells just slugs?
Snails are not shelled slugs, they just happen to share the taxonomic classification of gastropods.

©iStock.com/Gogiya

With all this information, we can finally answer the question: Are snails shelled slugs? Well, sort of. Gastropods without shells are called slugs. Shelled gastropods are known as snails. However, it is clear that snails and slugs are not the same animal . Snails and slugs evolved differently; snails are born with shells, while slugs don't. Stripping a snail's shell won't turn it into a slug; it will make it a dead snail.

Do snails need to replace their shells as they grow?

A common misconception is that snails find shells as they grow. While that may be true for hermit crabs, it's not true for snails. Snails are born with a small shell that slowly grows as they grow. When snail shells grow, they have a flexible material that expands the shell and hardens inside, adding layers over time.

Removing the snail from its shell will kill it, not turn it into a slug. Also, slugs won't take advantage of shells, even if given the chance.

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featured image

A beautiful multi-colored snail in the garden after the rain.
A beautiful multi-colored snail in the garden after the rain.

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about the author

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Colby Maxwell


Colby is a freelance writer from Charlotte, North Carolina. When he's not distracted by the backyard bird feeder, you can find him camping, exploring, and telling everyone around him what he's learned recently. There's a whole world to learn, and Colby is content to spend his life learning as much of it as he can!

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