''Mactra glauca'' 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 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 ...

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

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Mactridae Mactridae, common name the trough shells or duck clams, is a family (biology), family of saltwater clams, marine (ocean), marine bivalve mollusks in the order (biology), order Venerida. Description These clams have two short siphons, each with a ...

, the trough shells.

Appearance

''Mactra glauca'' has a broadly triangular, thin, glossy shell up to 115mm in length. The shell is creamy white with radiating pale brown rays, a 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 an ...

and a pale brown interior. The difference between ''M. glauca'' and '' M. stultorum'' is that the anterior cardinal tooth of the right valve is not parallel with the hinge line in ''M. glauca'', whereas in ''M. stultorum'' it is.

Right and left valve of the same specimen: Mactra glauca 01.jpg, Right valve Mactra glauca 02.jpg, Left valve

Distribution

''Mactra glauca'' is found on the continental shelf, from the south of England to the Mediterranean and West Africa. It is also found as fossils in 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 ...

from the

Eemian The Last Interglacial, also known as the Eemian, was the interglacial period which began about 130,000 years ago at the end of the Penultimate Glacial Period and ended about 115,000 years ago at the beginning of the Last Glacial Period. It cor ...

period.

Ecology

''Mactra glauca'' is a

suspension feeder Filter feeders are aquatic animals that acquire nutrients by feeding on organic matters, food particles or smaller organisms (bacteria, microalgae and zooplanktons) suspended in water, typically by having the water pass over or through a spec ...

which feeds on

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater Aquatic ecosystem, ecosystems. The name comes from the Greek language, Greek words (), meaning 'plant', and (), mea ...

. It burrows into clean sand, going down up to 7 cm if exposed by the tide.

References

Mactridae Bivalves described in 1778 {{bivalve-stub