Moon Snail – Hidden Treasure of the Tide Pool

by Gabbie Baillargeon

While wading through the intertidal zone you see hundreds, possibly thousands of small periwinkles covering what seems like every surface.  So it is rare that you get the chance to see the mysterious Moon Snail, who can usually be found deeper and farther out in a tide pool.  At first glance, they may seem small and ordinary, but upon holding one you malargey feel small muscle contractions as a thick gel begin to ooze from underneath the soft, silky foot.  Kids and adults alike will stare in amazement as they start to expand their mantle to cover your entire palm, and if you’re lucky their antennae will peak out of their comparatively small shell.  Periwinkles are only the size of a quarter, while moon snail shell’s are approximately the size of a half dollar with a large, purple mantle  Its shell is only 2.25 – 5.5 inches across, but the “body” or mantle can extend to nearly four times that diameter!  Unlike the common hermit crab who shops around for their shells, moon snails keep the same shell their whole life.  The foot, or portion that touches the ground, is covered in mucus and tiny hairs called cilia which aid in locomotion.  Moon snails excrete a clear, thick, sticky slime that serves two purposes: movement and protection.

Have you ever seen washed up shells that have a perfectly circular hole or cut out?  Well, you can thank moons snails for your new shell necklace!  Moon snails eat a variety of clam, mussels, and other mollusks – sometimes even other moon snails!  They do this by suctioning to their prey’s shell and using their radula, or tongue, to drill into it; while simultaneously secreting the enzyme carbonic anhydrate, which is believed to soften the shell for easier drilling.  Finally, the moon snail can digest its well deserved dinner.

_radula_03Life in the intertidal zone is a constant battle, as animals must be able to endure long periods of crashing waves, varying levels of oxygen, and the constant threat of predators.  In order to cope with the challenges of their habitat, the moon snail has developed unique anatomical structures.  Their skin is incredibly delicate, so the mucus serves to protect it from diseases and irritants found in the environment.  The moon snail’s mucus serves not only to provide a path to travel on, but also as a thick adhesive that aids in suctioning to rocks, so they do not wash away with the tide.  An amazing feature of moon snails is how they can increase the size of their mantle by absorbing extra seawater, their enlarged mantle enables them to dig under the sand or rocks to search for prey.  When they feel threatened, Moon snails can greatly decrease their body size and completely retract into their shell.  These extraordinary mollusks have perfectly adapted to the uncertainties of living in the intertidal zone.

Remember, if you are ever tide pooling and come across one of these guys, feel free to gently pick them up to get a closer look, just remember to put them back exactly where you found them!