''Mya truncata'', common name the blunt gaper or truncate softshell, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of edible saltwater

clam Clam is a common name for several kinds of bivalve molluscs. The word is often applied only to those that are edible and live as infauna, spending most of their lives halfway buried in the sand of the seafloor or riverbeds. Clams have two shel ...

, a marine bivalve

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

in the family

Myidae Myidae, common name the softshell clams, is a taxonomic family of marine bivalve molluscs in the order Myida. Genera Genera within the family Myidae include: * '' Cryptomya'' ( Conrad, 1848) **'' Cryptomya californica'' ( Conrad, 1837) – Cali ...

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 Soft-shell clams (American English) or sand gaper (British English/Europe), scientific name ''Mya arenaria'', popularly called "steamers", "softshells", "piss clams", "Ipswich clams", or "Essex clams" are a species of edible saltwater clam, a ...

''), 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) 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 The pallial sinus is an indentation or inward bending in the pallial line on the interior of a bivalve mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as mollusc ...

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 flippered marine mammal with a discontinuous distribution about the North Pole in the Arctic Ocean and subarctic seas of the Northern Hemisphere. The walrus is the only living species in the fami ...

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 ( cy, Gogledd Cymru) is a 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 Snowdonia N ...

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 slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fitting ...

of the shell, from the

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

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.

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