【Reading】たいらぎ

【English Name】Pen shell

The tairagi (pen shell) is a huge bivalve classified in the genus Atrina of the family Pinnidae, sometimes exceeding 30 cm in shell length, and the sushi topping uses its large adductor muscle. The Japanese name is said to have become established as a variation of "hiragai" (flat shell).

In Japan it ranges over inner-bay zones south of the Boso Peninsula, inhabiting seabeds of mixed sand and mud at depths of about 10-50 m. It lives in a posture as if stabbed into the seabed with the pointed end of its shell facing down, and depending on the individual the shell length exceeds 30 cm. Its lifespan is said to be about 6-7 years.

At sushi restaurants it is served as nigiri or sashimi; raw, it has a soft mouthfeel and a refreshing sweetness that stands out. Cooked, the texture gains firmness and the umami is drawn out more. The mantle (himo) is also used in dishes such as butter-grilling.

Today the main production areas are limited to Mikawa Bay, Harima Nada, the Bisan Seto, and Iyo Nada; in the Ariake Sea, resource decline has become serious, with fishing suspended since 1993 centered on the area along Isahaya Bay. It is also a shellfish widely and routinely eaten in Korea and China.

Two types exist—a scaled type with scale-like projections on the shell surface and a smooth scaleless type—and isozyme analysis has shown them to be genetically distinct species. The name "zubetairagi" has been proposed for the scaleless type.