Unknown. The Jackknife clam burrows deep and surfaces only to obtain food and water. There does not seem to be any negative effect of the clam on humans.
Ensis directus is a very fast burrower and very difficult to catch while it is still alive. However, when it is caught it can be sold and eaten like many other types of clams. E. directus is in season during the months of July-September.
(Great Northern Products. 2001; Cooper 1960)
Ensis directus is a filter feeder that filters water through its shell in order to obtain food. When feeding, E. directus stays very close to the surface and its siphons are sticking up through the surface. The water is drawn into the shell through the mantle cavity by cilia. These cilia cover the ctenidia, or gills, in the clam. It passes along the gills and combines with mucous. The food is now trapped and the cilia drive the food into the digestive tract.
(Jobin and Jobin 1997)
Ensis directus is found along the Atlantic coast from Canada to South Carolina. It lives in the intertidal zone or subtidal zone in the sand or muddy bottoms.
(Jobin and Jobin 1997, Gosner 1978)
Biogeographic Regions: atlantic ocean (Native )
Ensis directus lives in the sandy bottoms in the intertidal or subtidal zones along the Atlantic coast. It is usually found in colonies. It is not migratory and therefore it remains in its habitat year round.
(Gosner 1978)
Aquatic Biomes: coastal
Ensis directus has a thin, elongated shell that is slightly curved. It ranges from yellowish to dark brown in color. The length of E. directus is about six times its width. It can grow to be about 10 in. It has a coating around its shell to protect it from eroding in the mud or sand. Ensis directus is a bivalve, which means that its shell has two parts. The body of Ensis directus is surrounded by the mantle and the mantle is seperated into two parts. Each part of the mantle secretes a shell. The two shells are connected by an elastic ligament that allows for it to open and close. Both parts are usually identical and are made up of calcium carbonate and protein. It has a huge foot that allows it to move through water or to burrow in the sand. When the foot is extended all the way, it is almost as long as the clam's body.
(Alexander 1979; Lippson 1984)
Other Physical Features: ectothermic ; bilateral symmetry
US Federal List: no special status
CITES: no special status
There are separate male and female sexes in Ensis directus. The males release their sperm into the water and the sperm enters the female through openings. The eggs are fertilized in the interior of the gill by the sperm and these newly fertilized zygotes develop into larva. This larva is then released into the surrounding water. There are two larval stages. The first stage is the trocophore stage that has small larvae that are free swimming. They are pear shaped, translucent, and ciliated. The second stage is the veliger stage, which is also a free-swimming larval stage. It has a very long pelagic or plankton stage, which means that the larvae float freely within the water. This allows for the larvae to spread over large distances. This larva then settles onto the sand or mud and begins to develop into an adult. The body will develop as well as the mantle. The mantle will then secrete and line the shell.
(Kindersley 2001; Ogden 2001)
The Atlantic jackknife clam, Ensis leei,[1] also known as the bamboo clam, American jackknife clam or razor clam, is a large edible marine bivalve mollusc found on the North American Atlantic coast, from Canada to South Carolina. The species has also been introduced to Europe. The name "razor clam" is also used to refer to different species such as the Pacific razor clam (Siliqua patula) or Razor shell (Ensis magnus).
Jackknife clams live in sand and mud and are found in intertidal or subtidal zones in bays and estuaries. Its streamlined shell and strong foot allow Jackknife clams to burrow quickly in wet sand. Jackknife clams are also able to swim by propelling jets of water out of their shells. The Jackknife clam gets its name from their shell's extremely sharp rim and the overall shape bearing a strong resemblance to an old fashioned straight razor. Beachgoers can be injured when the shell is accidentally stepped on.[2]
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. Amos Winter of MIT has studied razor clams and how they bury themselves, in part by using a repurposed ant farm and glass beads. [1]
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 have ordinances regulating how many can be taken at a time.[3] 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.[4]
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.[5]
Jackknife clam, cooked, valves open The Atlantic jackknife clam, Ensis leei, also known as the bamboo clam, American jackknife clam or razor clam, is a large edible marine bivalve mollusc found on the North American Atlantic coast, from Canada to South Carolina. The species has also been introduced to Europe. The name "razor clam" is also used to refer to different species such as the Pacific razor clam (Siliqua patula) or Razor shell (Ensis magnus).
Jackknife clams live in sand and mud and are found in intertidal or subtidal zones in bays and estuaries. Its streamlined shell and strong foot allow Jackknife clams to burrow quickly in wet sand. Jackknife clams are also able to swim by propelling jets of water out of their shells. The Jackknife clam gets its name from their shell's extremely sharp rim and the overall shape bearing a strong resemblance to an old fashioned straight razor. Beachgoers can be injured when the shell is accidentally stepped on.
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. Amos Winter of MIT has studied razor clams and how they bury themselves, in part by using a repurposed ant farm and glass beads. [1]
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 have ordinances regulating 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.
![[1]](http://blogs.discovermagazine.com/notrocketscience/files/2012/05/Clam.jpg){kind=link}