MOON SNAILS

 

 

Creatures to admire, and if you’re a clam, to avoid! These are the big, round, full moon-shaped snails that wash in on the beaches after a storm. Sometimes they are found big enough to be a handful. They may be colored with pastels, brownish, or largely white. Occasionally, you will find one that looks blue – a blue moon, a treasure for sure!



We admire them, but clams and other mollusks try to get out of their way as they plow through the sand. They glide on a voluminous mucus covered body part called a foot. If these snails encounter a clam, they envelope it in their fleshy foot, and use a mouth part called a radula to drill a hole and eat their prey. You may have picked up clam shells neatly drilled as if someone were to bring an electric drill to the beach to make these holes. But the Moon snail is the carpenter who utilizes a built-in tool to create a beveled hole as an entrance to secure a meal. The radula is like a tongue with teeth that rasps until a hole is made. A chemical is secreted to help soften the hard shell, and the process is slow and methodical. If you look in shallow waters at low tide, you may see one of these large snails. Pick it up to see if it is in the process of drilling another animal. Moon snails are not discriminating, and will even drill another Moon snail if it is encountered.

Apart from its drilling apparatus, the Moon snail is unique because of the unusual shape in which we encounter its eggs. This snail discharges its eggs along with a volume of mucus that is molded by the foot and takes the shape of a round collar. Sand adheres to the collar and helps it retain its circular shape. When moist, the collar looks anything but alive, but underneath eggs can be found. If the collar washes up on the beach, it dries and becomes brittle. The shape of these egg masses is similar to the snail’s foot that laid these eggs. It will never be a complete circle since the snail starts the egg laying and terminates it without joining the ends. Snails pass through larval stages while attached to the collar, and emerge as tiny Moon snails.


Moon snails are found on sandy beaches, usually subtidally. They are eaten by gulls, and relished by Norwegians and other Europeans! If they are washed up by storm tides, they may survive by closing their door (operculum) made of a material similar to our fingernails. This door is brown, and may be found separately after the animal dies and washes up on the beach.

If you are lucky enough to find a live specimen, place it in a pan of salt water and watch it cruise! If you place it on wet sand, it will likely plow on its foot like a small bulldozer. In its natural habitat, the curved dome of its shell will most always be visible above the sandy bottom. You may find Sea Lettuce growing on some of the larger specimens, indicative of their not being totally underground. To prove to yourself that the animal can fit inside its shell, tickle the foot and watch it turn on its "sprinkling system" as it discharges its water supply to shrink in size. The operculum will seem to appear out of nowhere to seal the opening. Placing the animal again in water, will make it possible to open and expand its foot for foraging.

Empty shells are utilized by Hermit Crabs as housing. Hermit Crabs do not attack the snail to secure a house; they must wait until the snail dies before taken ownership of the moon-shaped shell. I have seen Hermit Crabs using shells with drilled holes, giving us a rare look at their soft insides temporarily encased in the shell.

So, go out in search of the snail named for the moon. You will surely end up standing in admiration for this predator found on our sandy beaches. If you don’t find the snail itself, string some of the shells it has drilled for you and wear a necklace in his honor.

 

11/23/98 Ronnie