Razor clam 12cm
Ensis directus, also known as the bamboo clam, American jackknife clam or razor clam (but note that "razor clam" sometimes refers to different species), is a large species of edible marine bivalve mollusc, found on the North American Atlantic coast, from Canada to South Carolina. It has also been introduced to Europe.
This clam lives in sand and mud and is found in intertidal or subtidal zones in bays and estuaries. Because of its streamlined shell and strong foot, it can burrow in wet sand very quickly, and is also able to swim. It gets its name from the rim of the shell being extremely sharp (stepping on one can cause injury) and the shape of the clam overall bearing a strong resemblance to an old fashioned straight razor.
At low tide the position of the Atlantic jackknife clam is revealed by a keyhole-shaped opening in the sand; when the clam is disturbed, a small jet of water squirts from this opening as the clam starts to dig. This species' remarkable speed in digging can easily outstrip a human digger, making the clam difficult to catch. Thus the species is not often commercially fished, even though it is widely regarded as a delicacy: in coastal Massachusetts, they are sought after in the summer by locals to make home cooked clam strips and most towns insist upon regulations dictating how many can be taken at a time. The easiest way to catch jackknives is to pour salt on the characteristic breathing holes. The clam will try to escape the salt by coming up out of its hole, at which point you can gently grab the shell and pull it out of the ground.
Predators of Ensis directus other than humans include birds, such as the ring-billed gull (Larus delawarensis) in North America and the Eurasian oystercatcher (Haematopus ostralegus) in Europe, and the nemertean worm Cerebratulus lacteus.
The Atlantic jackknife clam is now also found in northwestern Europe, where it is regarded as a harmful exotic species. It was first recorded in Europe in 1978/79, in the Elbe estuary.
The Atlantic jackknife clam has inspired a kind of biomimetic anchor in development by a team at the Massachusetts Institute of Technology, adapting the clam's digging method for use in keeping undersea cables and potentially watercraft anchored securely.