Moon snails, belonging to the family Naticidae, are large, marine gastropods with a global distribution in sandy and muddy substrates. These mollusks are recognized for their distinct, globular shells and their expansive, fleshy foot, which allows them to effectively “plow” through the sediment. While they may appear slow and innocuous, moon snails are highly active and specialized predators within their ecosystem. They are established as one of the most effective hunters in soft-bottom marine environments.
The Primary Diet
The primary diet of the moon snail consists almost entirely of other shelled mollusks. Their preferred prey are bivalves such as clams, oysters, and mussels, which they encounter while burrowing beneath the sand surface. They also prey upon other gastropods, including smaller snails and even other moon snails, exhibiting cannibalistic tendencies. They may also consume scaphopods (tusk shells) or small crustaceans, such as soldier crabs, though these are secondary food sources. This specialized diet of commercially valuable shellfish has earned them a reputation as a significant concern among shell fishermen.
The Unique Feeding Strategy
The moon snail’s method for breaching the shell of its prey is a sophisticated, two-part process that results in a perfectly circular, beveled hole. Once a prey item, such as a clam, is located, the moon snail envelops it completely with its muscular foot, often dragging it deeper into the sediment. This initial capture is followed by a precise physical and chemical attack on the prey’s shell.
The chemical phase begins with the application of the Accessory Boring Organ (ABO), a specialized gland located on the proboscis. This organ secretes a mixture of enzymes and an acidic substance, which may include hydrochloric acid, onto the shell surface. This secretion acts to demineralize and soften the calcium carbonate structure of the shell, preparing it for the mechanical drilling that follows.
The mechanical phase involves the radula. The moon snail uses this organ in a rasping motion, effectively drilling a hole into the softened spot on the shell. This combination of chemical softening and mechanical scraping is repeated in alternating cycles until the barrier is completely breached. Once the hole is complete, the moon snail inserts its proboscis, secretes digestive fluids to paralyze and liquidize the soft tissue, and consumes the resulting liquid mass.
Prey Detection and Selection
Moon snails are highly adept at locating their buried meals by utilizing chemoreception. They possess highly sensitive tentacles and chemosensory organs on their foot that detect waste products and other chemical cues released by buried mollusks. By following the concentration gradient of these chemical trails, the moon snail can effectively track and ambush its prey beneath the sand. Prey selection is guided by factors such as size and species preference, prioritizing items that offer a greater caloric return versus the time required to drill. They also exhibit site selectivity when drilling, often targeting a specific, thinner area of the shell, frequently near the umbo (the oldest part of the shell near the hinge).