Neptunea polycostata is a large marine gastropod mollusk belonging to the family Buccinidae, commonly referred to as whelks. It inhabits cold-temperate coastal waters of the northwest Pacific, particularly around northern Japan, the Sea of Okhotsk, and adjacent Russian waters. The genus name Neptunea derives from Neptune, the Roman god of the sea, reflecting its marine habitat, while the species epithet polycostata combines Greek poly- (“many”) and Latin costatus (“ribbed”), referring to the numerous pronounced ribs on the shell surface. In Japan, this species is known as Matsubu and Ezobora.

This species possesses a thick, spiraled shell with strong axial ribs and a muscular foot adapted for slow movement across benthic substrates. It is a predatory or scavenging snail, feeding on bivalves and other invertebrates, and plays a role in structuring benthic marine communities. As a food source, Neptunea polycostata is harvested for its firm, protein-rich foot muscle, which is consumed boiled, sliced for sashimi, simmered in soy-based broths, or incorporated into mixed seafood dishes in northern Japanese cuisine. The texture is characteristically chewy, and careful preparation is required to remove the digestive gland, which in some whelk species may contain accumulated toxins.

Nutritionally, the edible muscle is high in protein and relatively low in fat, containing marine-derived omega-3 fatty acids in modest amounts. Like other marine gastropods, it may contain bioactive peptides and trace minerals such as iodine and selenium. Certain Neptunea species have been associated with tetramine accumulation in the salivary glands, a neurotoxic compound that can cause transient symptoms if ingested in significant quantities; proper cleaning during preparation reduces this risk.