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Phylum Mollusca > Order Gastropoda
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For nature guides: introducing snails with shells
updated Oct 2016

What are snails?
Have you ever seen a snail? Yes, almost everyone knows what a snail looks like. The familiar land snails that we see, however, are the tip of the snail iceberg. Most snails are marine!

Snails belong to a group of animals called molluscs. Other molluscs include clams, octopus, squids and cuttlefishes!

Shall we look at shells?

  • Let's see how many different kinds of shapes of snail shells we can find! You can do this even with dead snail shells at high tide. Or in a shelter during rainy weather or while waiting for the tide to go down.
  • The shapes of snail shells tell us how they live. Can you guess from the shape and texture of this snail how it lives?
    • Smooth shiny shells: cowries have shiny shells because they cover the shell with their body.
    • Textured shells: The tiny bumps on knobbly periwinkles are believed to help keep it cool.
    • Round shells: Nerite snails are hard to grip and bounce away from slippery crab pincers to escape among the rocks.
    • Spikes may help deter predators: murex snail, spider conch
    • The flared lip of a conch helps prevent it from flipping over as it hops
    • Long tips protect the siphon: spiral melongena
    • Did you know some snails have hairy shells?! The hairy shell of a living spiral melongena traps sediments for camouflage. When it dies, the hairs fall off and the bright orange shell is often taken over by a hermit crab.

  • There's a big problem with a shell. It's got a big hole in it! Let's see the different ways the snails deal with this

    • Different shapes of shell openings
    • Shutting the opening with a door. Different kinds of doors and the advantage and disadvantage of each type.
      • Is the door thick and hard? Prevent crabs from breaking through or getting a grip on the door. (e.g., turban snails)
      • Or thin and flexible? Can be retracted deep into a coiling shell. (e.g., top shell snails)
      • Door with a lock! Nerite snails can lock their door shut!

    • Shutting the door and hanging on at the same time.
    • At low tide, periwinkles attach the lip of the shell to the surface with mucus then seal the shell opening tightly with a thin, horny operculum. Don't pick periwinkles off a rock! Left unattached, they may wash away when the tide comes in and they will die.
    • Limpets are snails with a conical shell (like a hat) and don't have an operculum. Instead, they clamp down tightly against the rock. Their grip is so strong that if you try to pry them off, you will hurt them. So please don't do this.

  • How do you think this snail died? Broken shells of dead snails tell stories of violent death.
    • Top of shell sliced off: probably by a crab
    • Shell has a hole: probably by another snail (e.g., moon snail).
    • Broken shells also allows you to illustrate the internal structure of a snail shell, how the animal can increase the size of its shell without ever coming out of the shell!

Living snails are fascinating!

  • Let's look at a living snail!
    • See how it moves! (If you can put it in a transparent container, you can see the broad foot)
    • How speedy can snails get? Pretty fast if it's a whelk going after the recent dead.
    • Can a snail hop? Yes it can if it's a conch.
    • Buldozing burrowers: see how the moon snail uses its oversized body to plough through the wet sand.
    • It has a pair of tentacles. Look also for the operculum. And other special body parts.
    • Some have a very long siphon to sniff out food (e.g, whelks)
    • Some snails cover their shells with their body (e.g cowries, moon snails)
    • Some snails don't move at all. Some mother cowries stay over their eggs to protect them. Other snails are tucked up inside their shells to avoid drying out at low tide.

Snail eggs

  • What do you think snails eggs look like?

This is a snail, meh?!

Snails are important to the ecosystem

  • Snails are part of the food chain. Can we think of some animals that might eat a snail? Some charismatic animals to highlight: crabs, shorebirds.

  • Snail shells are very important to hermit crabs! Hermit crabs have a soft backside and must insert this into an empty shell or they will get eaten. So don't take any shells home, whether the shell is pretty or ugly, complete or full of holes, big or small. Each shell is a potential hermit crab home!

  • Also, empty shells eventually break down into calcium that baby snails need to make their new homes.

Snails and you
We all love to eat snails!

  • Abalones are not clams (Class Bivalvia), they are snails (Class Gastropoda).
    • Do you know where it comes from? How was it caught? Was it farmed?
    • Do you know what it eats? (Here is a good time to explain red tide and other harmful algal blooms, etc and thus why they shouldn't eat wild collected snails).

Can I take this pretty snail shell home? Some approaches to dealing with this:

  • Shells are important to hermit crabs. (see above)
  • How long do you think you will look at this snail shell when you get home? One whole week? One whole day? Half a day? One hour? Usually it's around an hour. Why don't you look at it while we are on this walk and you can put it back at the end of the walk.
  • Let's take a photo of it instead. Especially to these visitor reasons for collecting
    • I want to find out more abou the shell when I get home.
    • My teacher told me to collect shells for a school project.

Snail myths to dispel

  • Snails never change shells. Snails create the shell that they live in and never move out of their shell while they are alive. They do not moult.

  • You can only remove a snail from its shell by killing it. All shells sold as souvenirs are obtained by harvesting living snails and killing them.

  • Not all snails are harmless. Some snails can kill. Cone snails can kill very quickly. But they are quite rare on our shores. If you are not sure, don't touch any snails or put them in your pockets.
Handling tips

Where to find snails? Many are stuck onto hard surfaces such as rocks, jetty pilings, sea walls. Often wedged in cracks, under stones and other cool wet spots. Some are tiny. Many dig into the sand or mud, others cling to seagrasses and seaweeds.

Be gentle! When overturning a rock to look at snails, be gentle so as not to crush animals under the rock, and plants living on top of the rock. Be sure to return the rock to exactly the way you found it, and ensure the visitors also learn that they should do this.

Don't disturb snails: Don't rip them off hard surfaces, or dig them up from the ground. Try to point out features without disturbing them.

Some mother snails like cowries, stay over their eggs. So don't remove snails.

Don't pick periwinkles off a rock! At low tide, periwinkles attach the lip of the shell to the surface with mucus then seal the shell opening tightly with a thin, horny operculum. Left unattached, they may wash away when the tide comes in and they will die.

Don't kill live snails! Don't force out living snails. Instead, use shells of dead snails (usually many can be found washed up on the high shore) to illustrate any stories or concepts you might have. If you leave a snail in a pool of water, it will usually come out and go about it's usual business. Be sure to put it back where you first found it.

Don't feed snails other marine life and don't feed snail to other marine life.

Displaying snails in a container here's some important points

Don't lose your snails. Most snails can crawl rapidly out of a container. So make sure you don't 'lose' any snails. And return them to where you found them after showing the snails to the visitors.

Don't mix snails with other kinds of snails or marine life. They might eat or poison one another. Many marine animals secrete poisons that can kill especially in a confined space.

Be gentle when showing snail egg capsules and sand collars. Explain that these contain living eggs and should not be damaged.
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