It’s SuperSnail!

Poulsbo WA – Along the mud flat shores of the Salish Sea, it is not unusual to encounter the large empty shells of Lewis Moon Snails. The shells are usually yellow white to pale brown in color, with a striking spiral radiating out from the center, set off by soft shades of orange and purple. They can be quite beautiful, even with cracks and chips along the opening lip, where a predator once tried to gain entry.  A fun find, the shell looks like it was built by SuperSnail and gives us an up close look at the amazing craftsmanship seen in the snail family.  Impressive as the shell may be, the enormous snail living inside is even more impressive.

The largest of all living marine snails, the Moon Snail’s massive foot surrounds the shell, enabling movement in search of its favorite snack, clams.  The snail will drill into the clam’s shell using a combination of seven rows of tiny teeth (radula) and a gland that secretes acidic enzymes to power through the shell. Over a day or so, the snail will suck and scrape the clam tissue out of its shell with a siphon formed with its foot.  The discarded shells are recognizable due to the small countersunk hole in the shell near the hinge.

Another amazing design feature is the snail’s system of movement.  The foot and mantle have a hollow network of sinuses into which water can be pumped and released enabling it to move and dig. When disturbed, it can quickly squirt water out and retreat into its shell, closing its amber colored door (operculum) behind it.  However, it is unable to stay in the shell for long, as it can’t breathe.

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When in an area frequented by moon snails, it is common to find the moon snail’s egg case.  It is a rubbery combination of sand and mucus that forms what looks like a collar, or even broken pottery scattered on the beach.  Thousands of eggs are embedded in the sand collar.  Eggs are laid between April and September, and will stay in the case for about six weeks, when the sand around them begins to disintegrate, releasing the tiny larvae into the water. The sand collar breaks down and become part of the sandy substrate once again.

As you walk the beach in late spring or early summer, look for the unmistakable egg cases strewn haphazardly across the beach.  If you are lucky, you might even find a Moon Snail in the final stage of rolling out its mucus covered egg case. In our region, we are treated to so many unusual sights on the seashore, and this is one of them. Take time to stop and marvel at this magnificent marine wonder.

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When and Where – Sandy or mudflat beaches. Kitsap Memorial State Park Beach and Scenic Beach State Park (both require Discover Pass) are two good locations to find the shells, egg cases and even active snails. Egg cases are primarily seen during the spring and summer months. If you find a living Moon Snail, be sure to wet your sunscreen/lotion free hands with sea water before gently touching it to help preserve its mucus layer.

Wonder Triggers for Young Trackers

  • Can you find the shell of a Lewis Moon Snail? When you study it carefully, what do you see? What do you wonder? Do you see evidence that a predator tried to crack into the shell when the snail was still living in it?
  • As the snail shell grew, it formed a little belly button type column through the center of the shell. (called an umbilicus) Can you find it? Some species of Moon Snails fill in that button with calcium and it looks more like an “outie” belly button!
  • What do you think this mollusk is called a “Moon Snail?” If you were the person who discovered it, what would you name it?
  • Can you find the Moon Snail’s egg case on the beach? It is safe to pick it up and study it.  What does it feel like? Look at it using a magnifying glass. Can you see the sand in it? Do you see anything else?
  • If you find a living Moon Snail that is out of its shell, watch it move on its giant foot.  See if you can find the tentacles, which look like two horns.
  • Moon Snails survive by eating other shelled animals.  Their favorite food appears to be clams.  They cover the clam with their big foot, then spend an average of 4 days drilling a hole in the shell with their sharp toothed radula (mouth) and using chemicals to help with the process. Can you find a clam shell that has a perfect circular hole drilled into it? Study the hole carefully. Are the edges smooth or rough? Is it a nearly perfect circle?

References and Resources

Slater Museum of Natural History


Central Coast Biodiversity

Oregon Coast Aquarium

WA Department of Ecology – ECOconnect

Images Sharon Pegany, Copyright 2018


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