''Abra alba'', or the white furrow shell, 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 ...

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

mollusc 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 esti ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Semelidae The Semelidae are a family of saltwater clams, marine bivalve molluscs in the order Cardiida. Description Members of this family have rounded or oval, elongated shells, much flattened. The two valves are connected by an internal ligament in c ...

. It occurs in the northeastern

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

and the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ea ...

, where it lives on the floor in shallow areas buried in soft sediments.

Description

''Abra alba'' can grow to up to long but a more usual size is 1.5 centimetres. It has a pair of thin brittle valves that are translucent, semi-shiny and a dirty white colour with a pale brown

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 and ...

. The shape is roughly oval and the posterior and anterior dorsal margins are almost straight and slope to rounded ends. Both margins are smooth and the anterior margin is a little longer than the posterior one. The valves have a sculpture of fine concentric lines and the growth stages of the animal are visible. The interior of the valves is somewhat glossy and the adductor muscle scars may be visible. The small brown ligament that holds the valves together is exterior.Marine Bivalve Shells of the British Isles
''Natural Museum Wales''. Retrieved August 8, 2011.

Distribution

''Abra alba'' is found on the coasts of northwest Europe and the

at depths down to . It is common around the British Isles and in the

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

. It prefers fine, silty sand, but is also found in mud or gravel.

Biology

''Abra alba'' feeds by means of a pair of separate long, extensible siphons, elongations of the mantle. It is mostly a

deposit feeder Detritivores (also known as detrivores, detritophages, detritus feeders, or detritus eaters) are heterotrophs that obtain nutrients by consuming detritus (decomposing plant and animal parts as well as feces). There are many kinds of invertebrates, ...

but is also able to feed on suspended particles as does the

tellin Tellin (; wa, Telin) is a municipality of Wallonia located in the province of Luxembourg, Belgium, in the Ardennes. On 1 January 2007 the municipality, which covers 56.64 km², had 2,386 inhabitants, giving a population density Popula ...

Tellina fabula ''Fabulina fabula'', the bean-like tellin, is a species of marine bivalve mollusc in the family Tellinidae. It is found off the coasts of northwest Europe, where it lives buried in sandy sediments. Bivalves are molluscs with a body compressed ...

'', a species with which it is often associated. The inhalant siphon gropes around widely over the surface of the substrate, actively drawing in detritus. In studies of

Liverpool Bay Liverpool Bay is a bay of the Irish Sea between northeast Wales, Cheshire, Lancashire and Merseyside to the east of the Irish Sea. The bay is a classic example of a region of freshwater influence. Liverpool Bay has historically suffered from red ...

, a

community A community is a social unit (a group of living things) with commonality such as place, norms, religion, values, customs, or identity. Communities may share a sense of place situated in a given geographical area (e.g. a country, village, tow ...

that includes ''A. alba'', ''

Phaxas pellucidus ''Phaxas pellucidus'', the transparent razor shell, is a species of marine bivalve mollusc in the family Pharidae. It is found buried in the seabed in coastal waters of northwest Europe, often in great numbers. Description ''P. pellucidus' ...

'' (the transparent razor shell) and '' Lagis koreni'' (the trumpet worm) is likely associated with more than one

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

. A large number of very small eggs are produced from May to August. The larvae probably have a lengthy period as part of the

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

before settling out. Juveniles grow fast during the summer but the ones that settle in autumn seem to delay their further development until the following spring. The lifespan is usually one year but can extend to two.

References

External link

{{Taxonbar, from=Q2568492 Semelidae Bivalves described in 1802 Taxa named by William Wood (zoologist)