While walking along Nauset spit in Orleans, I encountered this Northern Moon Snail (Lunatia heros) that had been caught out on the sand as the tide retreated. It was just starting to dig down into the wet sand to keep from drying out, as well as to avoid predators, such as gulls.

Moon snails also burrow to find their prey: bivalves. Since many clams are found more than 6 inches below the surface, moon snails must burrow to find them. Moon snails are able to push through the sand by using their large foot, which is able to inflate up to 4 times the snail’s shell volume through the uptake of water. To expand its body to move about, dig and/or feed, the moon snail takes water into its body.  To retract its body or to pull its body entirely back into its shell, the moon snail expels the water.

Once a moon snail finds a bivalve, like a clam, it uses its radula (a rough tongue-like scraping organ) to drill a hole through the clam’s shell. It targets the umbo (the knob or bump near the highest point closest to the hinge) of the clam’s shell. It is unclear whether this allows the snail the easiest position to hold onto its prey, or if this location better targets the bulk of soft body tissues, but perhaps it’s a little of both. As the moon snail uses its radula to scrape the shell, drilling is assisted by the secretion of acidic enzymes to soften and dissolve the calcium carbonate of the clam’s shell. When the hole is completed, the moon snail inserts its proboscis into the opening and consumes the contents inside.