Soft-shell clams (American English) or sand gaper (British English/Europe), scientific name Mya arenaria, popularly called "steamers", "softshells", "piss clams", "Ipswich clams", or "Essex clams" are a species of edible saltwater clam, a marine bivalve mollusk in the family Myidae.
Mya arenaria has a calcium carbonate shell, which is very thin and easily broken, hence the name "soft-shells" (as opposed to its beach-dwelling neighbors, the thick-shelled quahog).
This clam is found living approximately 3–8 in (7.6–20.3 cm) under the surface of the mud. It extends its paired siphons up to the surface, which draw in seawater, filter it for food, and expel it. The holes in the mud through which the water is drawn in and out can often be seen at low tide. Water may be visibly ejected from the siphon tips when pressure is applied to the surrounding mud. This makes the clams easier to locate when humans are clam digging.
These clams live buried in the sediment on tidal flats. While they are common in muddy areas, their name "arenaria" means sandy and they prefer a combination of sandy and muddy areas. They are well known as a food item on the coast of New England in the Western Atlantic Ocean; however, the range extends much farther north to Canada and south to the Southern states. They are also found in the Eastern Atlantic Ocean, for example in the UK, as well as in the North Sea's Wadden Sea (where they are the dominant large clam).
This species has become invasive on the Pacific Coast of North America, including Alaska, Canada and the continental United States. However M. arenaria originated in the Pacific Ocean during the Miocene. It extended its range in the early Pliocene to the Atlantic, including European waters. The Pacific and European populations became extinct some time in the early Pleistocene, leaving only the Northwest Atlantic population, which subsequently spread via humans to its current distribution. It also occurs in the Mediterranean Sea.
