Appearance
Jacknife 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 Jacknife clams to burrow quickly in wet sand. Jacknife clams are also able to swim by propelling jets of water out of their shells. The Jacknife 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.
Distribution
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.
Predators
Predators of "Ensis directus" other than humans include birds, such as the ring-billed gull in North America and the Eurasian oystercatcher in Europe, and the nemertean worm "Cerebratulus lacteus".References:
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