Ark Clams - Blood Clams

Found worldwide, Ark Clams are generally small, mostly 1 to 2 inches, but a few get tp 5 inches. Among the Ark Clams are the only shellfish that have red blood pigments (hemoglobin and myoglobin). This gives them better oxygen transfer allowing them to live in murky low oxygen environments in which most predators cannot thrive. These clams first appeared in the early Cretaceous, about 140 milion years ago. The fossil in the photo is of Anadara diluvii, which appeared about 23 milion years ago and went extinct only about 12,000 years ago, at the end of the last ice age.   Photo by Hectonichus distributed under license Creative Commons Attribution-ShareAlike 3.0 Unported.

More on Bivalve Mollusks.

Blood Cockle

These clams are native to intertidal zones of the Indo-Pacific region, from South Africa east to Australia and Polynesia, and as far north as northern Japan. they are of great economic value and farmed in mud flats in much of their range. They are sold frozen in Asian markets whole, half shell, or as cooked frozen meat. The photo specimens were purchased frozen from a large Asian market in Los Angeles (San Gabriel) for 2017 US $5.61 / pound - product of Vietnam. They can get as large as 2.4 inches, but the largest in this batch was 1.4 inches long and 1.1 inches thick. They weighed about 44 to the pound on average.

As packaged, they were minimally cooked, thus the open one has the appearance of being raw, and will look much less unappetizing when cooked a bit more. Edible yield, as removed from the shells was 3.9 ounces / pound (24%), but after a brief boil they dropped to 2.7 ounces / pound (17%) due to loss of liquid. Flavor (after the short boil) was quite good and clamy, but meatier than most clams of this size. The red clam juice is not very useful as it turns gray with cooking.

Safety:

Mexican Blood Clam

These clams are native to intertidal zones of the Eastern Pacific from Baja Mexico to Peru. They can grow to 3 inches long, but the photo specimens were up to 2.6 inches long and 1.7 inches thick. Average weight of the batch was 1.2 ounces each. The open clam in the photo is raw, and will look much less unappetizing when cooked. Yield raw was about 18%, and 14% cooked.

The photo specimens were purchased from a live seafood tank at a large Asian market in Los Angeles (San Gabriel) for 2017 US $4.69 / pound. They tend to not open when steamed, even for more than 10 minutes, but pried open, if they smell OK, they are edible.

Safety:

Akagai

These clams are native to intertidal zones of the Western Pacific, south of the northern island of Japan (Hokkaido) down the East Asian coasts to the Philippines and the Pacific side of Indonesia. The population is extensive along north central Australia, and some are found in southern New Zealand. They are similar to the Mexican Blood Clam, but rounder and even thicker. They are usually prepared as Sushi or Sashimi. These clams are both fished wild and farmed. They can grow to nearly 5 inches long, but in aquaculture are usually harvested at 2 inches and above.   Photo by A. C. Tatarinov contributed to the Public Domain.

To the left is a typical serving of Akagai over Sushi Rice. The slices may have been pounded flat to make them large enough to cover the rice. For sushi, 3 inch long clams are needed.   Photo by Arashiyama distributed under license Creative Commons Attribution-ShareAlike 3.0 Unported.

Noah's Ark Shell

This Ark Clam is native mostly to the Mediterranean and the coast of Morocco, but to a lesser extent down the west coast of Africa with a significant population off the tip of South Africa. I do not think this Ark Clam is a "blood clam", but, even though it's fished commercially in the Adriatic Sea (between Italy and the Balkans) and elsewhere, I can find almost no information about it. These clams are usually around 4 inches long when mature.   Photo by M.Violante distributed under license Creative Commons Attribution-ShareAlike 3.0 Unported.