''Mya truncata'',

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often con ...

the blunt gaper or truncate softshell, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of edible saltwater

clam Clam is a common name for several kinds of bivalve mollusc. The word is often applied only to those that are deemed edible and live as infauna, spending most of their lives halfway buried in the sand of the sea floor or riverbeds. Clams h ...

, a marine

bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...

in the family Myidae.

Description

Shells of ''Mya truncata'' can reach a size of about .MarLIN-The Marine Life Information Network
/ref>WoRMS
/ref> These bivalves are similar to the soft-shell clams ('' Mya arenaria''), but usually they are smaller. Moreover, their shells are less elongated. Valves are rounded in the anterior end and truncated in the posterior end, with a large gape allowing the passage of an extensible siphon that can reach four times the length of the shell. The siphon can be retracted completely into the shell. The two valves are triangular and convex, but the right valve is more convex than the left one. The siphon is protected by a horny sheath and it is provided with small tentacles at its end. The outer surface of the valves is covered with concentric growth lines. It is whitish, while the outermost layer of the valves (

periostracum The periostracum ( ) is a thin, organic coating (or "skin") that is the outermost layer of the shell of many shelled animals, including molluscs and brachiopods. Among molluscs, it is primarily seen in snails and clams, i.e. in gastropods an ...

) may be yellowish, light olive or dark brown. The hinge of the left valve shows a spoon-shaped projection, to which the ligaments are attached. The pallial sinus is deep and broad.

Biology

Reproduction is sexual, the gametes of both sexes being expelled into the water, then the free larvae attach themselves to rocks. These clams filter the sea water in order to feed on bacteria, diatoms and larvae of invertebrates. In some years, the reproductive cycle fails completely. These clams are the main food of the

walrus The walrus (''Odobenus rosmarus'') is a large pinniped marine mammal with discontinuous distribution about the North Pole in the Arctic Ocean and subarctic seas of the Northern Hemisphere. It is the only extant species in the family Odobeni ...

ses ('' Odobenus rosmarus''). They feed on these clams by raking the mud with their tusks and sieving out the clams.

Distribution and habitat

This species is widespread over the Arctic seas and extends to the Bay of Biscay, to the West Atlantic coast and to Sakhalin on the Pacific coast. It has been reported also in the waters around Japan.Catalogue of life
/ref> ''Mya truncata'' lives from the lower shore up to depths of 70 m, burrowed in sand or sandy mud.

Gallery

File:Mya truncata shell.jpg, Shell of ''Mya truncata'' from

North Wales North Wales ( ) is a Regions of Wales, region of Wales, encompassing its northernmost areas. It borders mid Wales to the south, England to the east, and the Irish Sea to the north and west. The area is highly mountainous and rural, with Snowdon ...

File:Mya truncata2-H.jpg, Whole animal and left

valve A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or Slurry, slurries) by opening, closing, or partially obstructing various passageways. Valves are technically Pip ...

of the shell, from the

North Sea The North Sea lies between Great Britain, Denmark, Norway, Germany, the Netherlands, Belgium, and France. A sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian Se ...

File:Mya truncata 001.png, ''Mya truncata'' : a) foot b) siphon sheath c) exhalant siphon d) inhalant siphon e) umbones or beaks f) anterior g) posterior end of the shell File:Mya-truncata in-situ hg.jpg, Shells of ''Mya truncata'' in subrecent sediments on the coast of

Spitsbergen Spitsbergen (; formerly known as West Spitsbergen; Norwegian language, Norwegian: ''Vest Spitsbergen'' or ''Vestspitsbergen'' , also sometimes spelled Spitzbergen) is the largest and the only permanently populated island of the Svalbard archipel ...

References

Bibliography

* Clay, E., 1966. Literature survey of the common fauna of estuaries. 12. Mya arenaria L., Mya truncata L. Imperial Chemical Industries Limited, Brixham Laboratory, BL/A/707. * Fish, J.D. & Fish, S., 1996. A student's guide to the seashore. Second edition. Cambridge: Cambridge University Press. * Hayward, P., Nelson-Smith, T. & Shields, C. 1996. Collins pocket guide. Sea shore of Britain and northern Europe. London: HarperCollins. * Hayward, P.J. & Ryland, J.S. (ed.) 1995b. Handbook of the marine fauna of North-West Europe. Oxford: Oxford University Press. * Tebble, N., 1976. British Bivalve Seashells. A Handbook for Identification, 2nd ed. Edinburgh: British Museum (Natural History), Her Majesty's Majesty's Stationery Office. *Guido Poppe and Yoshihiro Goto: European Seashells Volume 2 (Scaphopoda, Bivalvia, Cephalopoda). 221 S., Verlag Christa Hemmen, Wiesbaden 1993 (2000 unv. Nachdruck) *Linnaeus, C. (1758). Systema Naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Editio decima, reformata. Laurentius Salvius: Holmiae. ii, 824 pp *Rainer Willmann: Muscheln der Nord- und Ostsee. 310 S., Neumann-Neudamm, Melsungen 1989, *Teresa Amaro, Gerard Duineveld und Paul Tyler: Does Mya truncata reproduce at its southern distribution limit? Preliminary information. Journal of Shellfish Research, 24: 24-28, New Orleans, ISSN 0730-8000 *Turgeon, D. D., J. F. Quinn, Jr., A. E. Bogan, E. V. Coan, F. G. Hochberg, W. G. Lyons, et al. (1998) Common and scientific names of aquatic invertebrates from the United States and Canada: Mollusks, 2nd ed., American Fisheries Society Special Publication 26 {{Taxonbar, from=Q320415 Clams Myidae Marine molluscs of Europe Marine molluscs of North America Molluscs of the Atlantic Ocean Molluscs of the Pacific Ocean Molluscs of the United States Western North American coastal fauna Commercial molluscs Molluscs described in 1758 Taxa named by Carl Linnaeus