Akagai, ark shell, blood clam あかがい、赤貝
(Anadara broughtonii)
The Japanese ark shell has beautiful red flesh. Adult blood clams can reach a shell length of 12 cm and are commercially harvested in China, Japan, and Korea as a source of sashimi. The shell lives at the sandy bottoms of shallow waters at the mouth of rivers or in bays. It has 42 radial ribs in its shell. Like other bivalves of the ark clam family, the respiratory pigment is erythrocruorin, which has iron porphyrin as a prosthetic group like hemoglobin, so the blood is red, which is the origin of the name. When the shell is opened, a lot of the blood comes out, which can be somewhat shocking to see, as it is unexpected in the case of shellfish.
[Akagai on sushi]
Popular on sushi since the 19th century, it is still the most popular sushi shell due to its delicious aroma. The best season (shun) is spring. The meat is usually washed in vinegar. Popular are organs such as the sphincter. In addition to being used as a topping on sushi, it is also eaten raw with soy sauce and wasabi dipping sauce, or baked (sometimes in the shell).
Photo from Wikimedia Commons
Japanese Food Dictionary