''Mytilaster minimus'', the dwarf mussel or variable mussel, is a species of

mussel Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and Freshwater bivalve, freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other ...

from sea and brackish waters of the Mediterranean Sea.

Description

The shell of ''Mytilaster minimus'' has a smooth and glossy surface which is marked with faint growth rings. The exterior colour of the shell is reddish brown, the inside is pearly. The shell has an elongated shape, with the apex located at one end and a reduced hinge which has no teeth. The length of the shell measures 10-12mm.

Distribution and biology

''Mytilaster minimus'' is distributed throughout the Mediterranean Sea and is also found off

Gran Canaria Gran Canaria (, ; ), also Grand Canary Island, is the third-largest and second-most-populous island of the Canary Islands, an archipelago off the Atlantic coast of Northwest Africa which is part of Spain. the island had a population of that co ...

and

Tenerife Tenerife (; ; formerly spelled ''Teneriffe'') is the largest and most populous island of the Canary Islands. It is home to 43% of the total population of the archipelago. With a land area of and a population of 978,100 inhabitants as of Janu ...

in the

Canary Islands The Canary Islands (; es, Canarias, ), also known informally as the Canaries, are a Spanish autonomous community and archipelago in the Atlantic Ocean, in Macaronesia. At their closest point to the African mainland, they are west of Morocc ...

It forms colonies on hard substrates in coastal waters and in brackish water such as coastal lagoons. This species can colonise rather

oligotrophic An oligotroph is an organism that can live in an environment that offers very low levels of nutrients. They may be contrasted with copiotrophs, which prefer nutritionally rich environments. Oligotrophs are characterized by slow growth, low rates of ...

areas but in more

eutrophic Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phytoplank ...

regions the larger Mediterranean edible mussel ''

Mytilus galloprovincialis The Mediterranean mussel (''Mytilus galloprovincialis'') is a species of bivalve, a marine mollusc in the family Mytilidae. It is an invasive species in many parts of the world, and also an object of aquaculture. Systematics ''Mytilus gall ...

'' can be found among and, in places displace ''M. minimus''. The

whelk Whelk (also known as scungilli) is a common name applied to various kinds of sea snail. Although a number of whelks are relatively large and are in the family Buccinidae (the true whelks), the word ''whelk'' is also applied to some other marine ...

'' Stramonita haemastoma '' is an important predator of ''M. minimus'' but where the invasive Lesspesian migrant '' Brachidontes pharaonis'' is found, the whelk prefers to prey on that species over the native

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 ...

s and

barnacle A barnacle is a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in eros ...

Threats

''Mytilaster minimus'' is threatened by the invasive ''Brachidontes pharaonis'' which is displacing it in many areas of theMediterranean. The invasive mussel is better able to tolerate higher temperatures and salinities than ''M. minimus'', and in recent years average water temperatures in the Mediterranean have been increasing. ''B. pharaonis'' interferes with the recruitment of ''M. minimus'' and has a detrimental effect on its survival and growth. In some area of Israel ''M. minimus'' is now rarely encountered M. minimus is not tolerant of pollution and this can cause colonies to disappear.

References

{{Taxonbar, from=Q13871836

minimus The Minimus books are a series of school textbooks, written by Barbara Bell, illustrated by Dr. Helen Forte, and published by the Cambridge University Press, designed to help children of primary school age to learn Latin. The books espouse some of ...

Bivalves described in 1795 Taxa named by Giuseppe Saverio Poli