The habitat for ark shells range from the near waters of Japan to the East China Seas. The other name for ark shells, “blood shell,” derives from the fact that they are red as if they were dyed in blood. However, this is not due to their pigment, but as their blood actually contains hemoglobin, just like mammals. Ark shells usually live in muddy seabeds, and they open their mouth to feed on planktons. When made into sushi, smaller ark shells are considered to be more precious than the larger ones. Sushi made with fish from Tokyo Bay are called Edo-Mae Zushi, which has been famous for ark shell sushi. Still, in the recent years, imported or domestically farmed sushi have been used more often.
Ark shells are rich in iron as they contain hemoglobin, and they can be highly recommended for people with anemia, as they are also rich in vitamin B12s. Another characteristic feature is the amino acid, succitnate, which gives the flavor unique to shells. It is suitable for women, as they contain glutathione which is good for detoxification.