Razor shell
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Ensis arcuatus |
The razor shell, Ensis arcuatus, also called razor clam or Razor fish, is a bivalve of the family Solenidae. It is found on sandy beaches in Northern Europe, although it prefers coarser sand than its relatives E. ensis and E. siliqua.[1]
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[edit] Description
It is known for its elongated, rectangular shape, whose similarity to the straight razor gives it its name. The razor shell has been known to reach 20cm in length. The dorsal margin is straight while the ventral margin is curved. It can easily be confused with the slightly shorter (15 cm) and more curved E. ensis (in which both front and back are curved in parallel).
Razor shells have a fragile shell, with open ends. The shell is smooth on the outside and whitish in colour, with vertical and horizontal reddish-brown or purplish-brown markings separated by a diagonal line. The periostracum is olive-green. The inner surface is white with a purple tinge and the foot is creamy white with brown lines .
[edit] Habits
The razor shell lives under the sand, using its powerful foot to dig to a safe depth. In fact, the razor shell can dig faster than a man.[2] Its digging activity comprises six stages, repeated cyclically. a digging cycle involves integration of the muscular foot (which takes up a large part of the body) with the opening and closing of the valve and one end. The foot is inflated hydraulically, extend down into the sand and anchoring the animal. Deflation of the foot then draws the shell down. The razor shell also squirts water down into the sand, removing loose sand from its path. the foot is thought to exert a pressure of 2 Kg/Cm2[3]
Its presence is revealed by a keyhole-shaped hole in the sand, made by its siphons during suspension feeding for plankton.
[edit] Reproduction
In the razor shell sexual development is highly synchronous. During the summer, they are in the sexual rest stage, and gametogenesis begins at the start of autumn. In winter and spring consecutive spawns take place, interrupted by gonadal restoration periods.[4]
[edit] Vulnerability
Many intertidal populations of razor shell have been declined due to overfishing; the species is in decline in many areas.
Razor shells are very sensitive to minor perturbations in, for instance, salinity and temperature. they can be removed from their burrows by pouring in salt.[5]
[edit] Disease
Razor shells have been found to be vulnerable to germinoma, a variety of tumour.[6]
