Ensis ensis
Encyclopedia
Ensis ensis, or the sword razor, is a marine bivalve
mollusc
in the family
Pharidae
. It lives buried in the sand and is found off the coasts of north west Europe.
Bivalves are molluscs with a body compressed between two usually similar shell valves
joined by an elastic ligament. There are teeth at the edge of the shell and the animal has a muscular foot, gill
s, siphons, mouth and gut and is surrounded by a mantle
inside its shell.
is olive green and the foot is reddish. Two identifying features are that the posterior adductor muscle is positioned some one and a half times its own length from the pallial sinus and that the muscle that retracts the foot is posterior to the insertion point of the ligature. Ensis siliqua and Ensis arcuatus are rather similar species that can be found in the same localities but both are less curved.
and Norway
to the Atlantic coast of Spain
. It is common round the coasts of Britain.
and the low intertidal zone. When covered with water it remains close to the surface but when disturbed or when the substrate is exposed it descends to half a metre below the surface and can tunnel with great rapidity. It has two short siphons that normally extend to the sand surface. It draws in water through one and expels it through the other. By this means it both respires and extracts food particles from the water at the same time. A keyhole shaped depression in the sand may be the only sign that the mollusc lies beneath.
E. ensis becomes mature at about three years old and may live for ten. Reproduction takes place in the spring and the larva
e are pelagic
and form part of the zooplankton
. After about a month they settle out and burrow into the substrate.
, and the bivalve molluscs Tellina fabula
and Chamelea gallina
.
Bivalvia
Bivalvia is a taxonomic class of marine and freshwater molluscs. This class includes clams, oysters, mussels, scallops, and many other families of molluscs that have two hinged shells...
mollusc
Mollusca
The Mollusca , common name molluscs or mollusksSpelled mollusks in the USA, see reasons given in Rosenberg's ; for the spelling mollusc see the reasons given by , is a large phylum of invertebrate animals. There are around 85,000 recognized extant species of molluscs. Mollusca is the largest...
in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Pharidae
Pharidae
Pharidae is a family of clams related to the razor shells , a family which includes Pharidae by some authorities.-Genera:* Afrophaxas Cosel, 1993* Cultellus Schumacher, 1817* Ensiculus H...
. It lives buried in the sand and is found off the coasts of north west Europe.
Bivalves are molluscs with a body compressed between two usually similar shell valves
Bivalve shell
A bivalve shell is part of the body, the exoskeleton or shell, of a bivalve mollusk. In life, the shell of this class of mollusks is composed of two parts, two valves which are hinged together...
joined by an elastic ligament. There are teeth at the edge of the shell and the animal has a muscular foot, gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
s, siphons, mouth and gut and is surrounded by a mantle
Mantle (mollusc)
The mantle is a significant part of the anatomy of molluscs: it is the dorsal body wall which covers the visceral mass and usually protrudes in the form of flaps well beyond the visceral mass itself.In many, but by no means all, species of molluscs, the epidermis of the mantle secretes...
inside its shell.
Description
E. ensis has a pair of narrow curved shells that grow up to ten centimetres in length and are thin and rather brittle. The edges are parallel, tapering slightly towards the posterior and are off white with transverse bands of brown. The shell is sculpted with fine co-marginal lines and the annual growth lines can be seen. The inner side of the shell is white with a purplish sheen. The periostracumPeriostracum
The periostracum is a thin organic coating or "skin" which is the outermost layer of the shell of many shelled animals, including mollusks and brachiopods. Among mollusks it is primarily seen in snails and clams, i.e. in bivalves and gastropods, but it is also found in cephalopods such as the...
is olive green and the foot is reddish. Two identifying features are that the posterior adductor muscle is positioned some one and a half times its own length from the pallial sinus and that the muscle that retracts the foot is posterior to the insertion point of the ligature. Ensis siliqua and Ensis arcuatus are rather similar species that can be found in the same localities but both are less curved.
Distribution
E. ensis occurs off the coasts of north west Europe, from the Baltic SeaBaltic Sea
The Baltic Sea is a brackish mediterranean sea located in Northern Europe, from 53°N to 66°N latitude and from 20°E to 26°E longitude. It is bounded by the Scandinavian Peninsula, the mainland of Europe, and the Danish islands. It drains into the Kattegat by way of the Øresund, the Great Belt and...
and Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
to the Atlantic coast of Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
. It is common round the coasts of Britain.
Biology
E. ensis burrows into clean or silty sand on the seabed in the neritic zoneNeritic zone
The neritic zone, also called coastal waters, the coastal ocean or the sublittoral zone, is the part of the ocean extending from the low tide mark to the edge of the continental shelf, with a relatively shallow depth extending to about 200 meters...
and the low intertidal zone. When covered with water it remains close to the surface but when disturbed or when the substrate is exposed it descends to half a metre below the surface and can tunnel with great rapidity. It has two short siphons that normally extend to the sand surface. It draws in water through one and expels it through the other. By this means it both respires and extracts food particles from the water at the same time. A keyhole shaped depression in the sand may be the only sign that the mollusc lies beneath.
E. ensis becomes mature at about three years old and may live for ten. Reproduction takes place in the spring and the larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e are pelagic
Pelagic zone
Any water in a sea or lake that is not close to the bottom or near to the shore can be said to be in the pelagic zone. The word pelagic comes from the Greek πέλαγος or pélagos, which means "open sea". The pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes...
and form part of the zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
. After about a month they settle out and burrow into the substrate.
Ecology
E. ensis is often found living in association with other burrowing animals including the sea potato, Echinocardium cordatumEchinocardium cordatum
Echinocardium cordatum, or the sea potato, is a sea urchin in the family Loveniidae. It is found in sub-tidal regions in temperate seas around the world and lives buried in the sandy sea floor.-Description:...
, and the bivalve molluscs Tellina fabula
Tellina fabula
Tellina fabula is a species of marine bivalve mollusc in the family Tellinidae. It is found off the coasts of north west Europe where it lives buried in sandy sediments....
and Chamelea gallina
Chamelea gallina
Chamelea gallina is a species of small saltwater clam, a marine bivalve mollusc in the family Veneridae, the venus clams.-Taxonomy:Linnaeus originally described Venus gallina from the Mediterranean in 1758. Other zoologists may have consequently assumed that Da Costa's 1778 Pectunculus striatulus...
.