Blue mussels
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The blue mussel (''Mytilus edulis''), also known as the common mussel, is a medium-sized edible marine bivalve mollusc in the
family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
Mytilidae Mytilidae are a family of small to large marine and brackish-water bivalve molluscs in the order Mytilida. One of the genera, '' Limnoperna'', even inhabits freshwater environments. The order has only this one family which contains some 52 gener ...
, the mussels. Blue mussels are subject to commercial use and intensive aquaculture. A species with a large range, empty shells are commonly found on beaches around the world.


Systematics and distribution


The ''Mytilus edulis'' complex

Systematically blue mussel consists of a group of (at least) three closely related taxa of mussels, known as the ''Mytilus edulis'' complex. Collectively they occupy both coasts of the North Atlantic (including the
Mediterranean 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 Europe, Western and Southern Europe and Anatolia, on the south by North Africa ...
) and of the North
Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contine ...
in temperate to polar waters, as well as coasts of similar nature in the Southern Hemisphere. The distribution of the component taxa has been recently modified as a result of human activity. The taxa can hybridise with each other, if present at the same locality. *''Mytilus edulis'' sensu stricto: Native to the North Atlantic. *''
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 ...
'', the Mediterranean mussel: Native in the Mediterranean, the Black Sea and Western Europe. Introduced in the temperate North Pacific,
South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...
and elsewhere in the Southern Hemisphere. *''Mytilus planulatus'', the New Zealand blue mussel, a distinct lineage native to the Southern Hemisphere along the southern coast of Australia, Tasmania and New Zealand *'' Mytilus platensis'' (junior synonym ''M. chilensis''), the Chilean mussel: Temperate and sub-Antarctic waters of South America and the Kerguelen Islands. *''
Mytilus trossulus ''Mytilus trossulus'', the bay mussel or foolish mussel, is a medium-sized edible marine bivalve mollusc in the family Mytilidae. ''Mytilus trossulus'' is one of the three principal, closely related taxa in the ''Mytilus edulis'' complex of blue ...
'': North Pacific, northern parts of the North Atlantic,
Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden and the North and Central European Plain. The sea stretches from 53°N to 66°N latitude and ...
.


''Mytilus edulis'', strict sense

The Atlantic blue mussel is native on the North American Atlantic coast, but is found intermixed with ''M. trossulus'' north of
Maine Maine () is a state in the New England and Northeastern regions of the United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Canadian provinces of New Brunswick and Quebec to the northeast and ...
. In Atlantic Canada, ''M. trossulus'' was found to have smaller shell growth values than ''M. edulis'' and contain less meat than ''M. edulis.'' Keeping this in mind, ''M. edulis,'' under raft culture conditions, is estimated to have an economic value of 1.7 times ''M. trossulus.'' In Europe it is found from French Atlantic coast northwards to Novaya Zemlya and
Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its s ...
, but not in the
Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden and the North and Central European Plain. The sea stretches from 53°N to 66°N latitude and ...
. In France and in the
British Isles The British Isles are a group of islands in the North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner and Outer Hebrides, the Northern Isles, ...
, it makes
hybrid zone A hybrid zone exists where the ranges of two interbreeding species or diverged intraspecific lineages meet and cross-fertilize. Hybrid zones can form ''in situ'' due to the evolution of a new lineage but generally they result from secondary contact ...
s with ''M. galloprovincialis'', and also is sometimes intermixed with ''M. trossulus''. The genetically distinct lineage of ''M. edulis'' present in the Southern Hemisphere has been attributed to subspecies '''' (now '' Mytilus platensis'').


Habitat

Blue mussels are boreo-temperate invertebrates that live in
intertidal The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species ...
areas attached to rocks and other hard substrates by strong (and somewhat elastic) thread-like structures called
byssal thread A byssus () is a bundle of filaments secreted by many species of bivalve mollusc that function to attach the mollusc to a solid surface. Species from several families of clams have a byssus, including pen shells ( Pinnidae), true mussels (Mytili ...
s, secreted by byssal glands located in the foot of the mussel.


Description

The shape of the shell is triangular and elongated with rounded edges. The shell is smooth with a sculpturing of fine concentric growth lines but no radiating ribs. The shells of this species are purple, blue or sometimes brown in color, occasionally with radial stripes. The outer surface of the shell is covered by the periostracum which as eroded, exposes the colored prismatic calcitic layer. Blue Mussels are semi-sessile, having the ability to detach and reattach to a surface allowing the mollusk to reposition itself relative to the water position.
Right and left valve of the same specimen: File:Mytilus edulis 001.jpg, Right valve File:Mytilus edulis 002.jpg, Left valve var. ''flavida'' File:Mytilus edulis var. flavida 01.jpg, Right valve File:Mytilus edulis var. flavida 02.jpg, Left valve


Reproduction

Mussels have separate sexes. Once the sperm and eggs are fully developed they are released into the water column for fertilization. Although there are about 10,000 sperm per egg, large proportions of eggs deposited by blue mussels are never fertilized. As few as 1% of larvae that do mature ever reach adulthood. The majority are eaten by predators before completing metamorphosis. The reproductive strategy seen in blue mussels is characteristic of planktotrophs. By minimizing nutrients in egg production to the bare minimum they are able to maximize the number of gametes produced. If the adult mussels are stressed during the beginning of gametogenesis, the process is terminated. When stressed while fresh gametes are present, adult mussels reabsorb gametes. Larvae viability is also affected by the condition of parents: high water temperatures, pollutants and scarcity of food, during gamete production. The reduction in viability is probably due to the lack of
lipid Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids includ ...
reserves distributed to the eggs.


Larval development

Larval development can last from 15 to 35 days depending environmental conditions including salinity and temperature, as well as location. Larvae originating from
Connecticut Connecticut () is the southernmost state in the New England region of the Northeastern United States. It is bordered by Rhode Island to the east, Massachusetts to the north, New York to the west, and Long Island Sound to the south. Its capita ...
mature normally at , though at normal development occurs at salinities between 15 and 35 ppt and at 35 ppt at . The first stage of development is the ciliated embryo, which in 24-hours for fertilization form the
trochophore A trochophore (; also spelled trocophore) is a type of free-swimming planktonic marine larva with several bands of cilia. By moving their cilia rapidly, they make a water eddy, to control their movement, and to bring their food closer, to captur ...
. At this point although mobile, it is still reliant on the yolk for nutrients. Characterized by a functional mouth and alimentary canal the veliger stage also has cilia which are used for filtering food as well as propulsion. A thin translucent shell is secreted by the shell gland forming the notable straight hinge of the
prodissoconch A prodissoconch (meaning first or earliest or original shell) is an embryonic or larval shell which is present in the larva of a bivalve mollusk (clams, scallops, oysters, etc.). (The homologous structure in gastropods (snails) is called the pr ...
I shell. The veliger continues to mature forming the prodissoconch II shell. In the end stage of veliger development photosensitive eye spots and elongated foot with a byssal gland are formed. Once the pediveliger is fully developed, its foot extends and makes contact with substrate. The initial contact with the substrate is loose. If the substrate is suitable, the larva will metamorphoses into the juvenile form, plantigrade, and attach byssus threads. The mussel will remain in that state until reaching 1-1.5mm in length. This attachment is the prerequisite for the foundation for the blue mussel population. In sheltered environments large masses sometimes form beds which offer shelter and food for other invertebrates. Byssal thread are secreted by byssal glands located in the foot of the mussel, and are made up of polyphenolic proteins which serve as a bioadhesive.


Aggregation and mussel bed formation

Blue mussels often form aggregations, where they attach to each other using byssus threads. These are collagenous protein strands used for attachment. The type of aggregation depends on
population densities Population density (in agriculture: standing stock or plant density) is a measurement of population per unit land area. It is mostly applied to humans, but sometimes to other living organisms too. It is a key geographical term.Matt RosenberPopu ...
. When densities are low, for example in mussel fields – short-lived mussel populations – clumped distribution patterns are seen. The rate of aggregation is aided by the presence of predator cues. Several explanations for aggregate formation have been offered, such as increase of reproductive success in low density populations, resisting of
wave action In fluid dynamics, a wind wave, water wave, or wind-generated water wave, is a surface wave that occurs on the free surface of bodies of water as a result from the wind blowing over the water surface. The contact distance in the direction o ...
, and defence against predators. It is, however, still unclear what the main purpose is and aggregation might have different purposes under different circumstances. Mussel beds are persistent, dense mussel populations. Beds generally form from fields that persist long enough to establish a dense population. In high density aggregations, growth of blue mussels at the centre of the aggregation is reduced, likely due to a reduction in food availability. When possible, mussels will thus migrate to lower densities on larger scales (>7.5 cm), but aggregate on small scales (<2.0 cm). In areas where blue mussels are threatened, such as the Wadden Sea, it is of great importance to enhance the survival of mussel fields, of which mussel aggregates are the primary component.


Predators

Predation of blue mussels is greatest during the three weeks it spends as a planktonic larva. During this stage it is susceptible to
jellyfish Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrell ...
and
fish larva Ichthyoplankton (from Greek: ἰχθύς, , "fish"; and πλαγκτός, , "drifter") are the eggs and larvae of fish. They are mostly found in the sunlit zone of the water column, less than 200 metres deep, which is sometimes called the epi ...
e through adults. Once it metamorphoses the mussel is still restricted by predation, with smaller mussels with thinner, weaker shells most affected. Once the shells becomes stronger, blue mussels are preyed upon by
sea stars Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea (). Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish ar ...
such as '' Asterias vulgaris'' as well as by several species of sea gulls. The capability of shell thickening by mussels has become a very effective defense mechanism. In the presence of predators a mussel is able to increase shell thickness 5 to 10 percent, which in turn makes opening the shell take 50 percent more time. Small mussels are also eaten by the dog whelk, ''
Nucella lapillus The dog whelk, dogwhelk, or Atlantic dogwinkle (''Nucella lapillus'') is a species of predatory sea snail, a carnivorous marine gastropod in the family Muricidae, the rock snails. ''Nucella lapillus'' was originally described by Carl Linnaeus ...
''. The blue mussel is host to a wide range of parasites, but these parasites usually do not cause much damage. Blue Mussels are able to fight off one species of predator at a time such as sea star(''Asterias Rubens (=Asterias Vulgaris'')) or green crabs (''Carcinus maenas''). They use their inducible defenses to strengthen their adductor muscle or grow thicker shells. When faced with two species at a time, they are no longer able to use their defenses and can be killed more easily.


Uses and ecosystem services

Blue mussels are
filter feeders Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...
and play a vital role in estuaries by removing bacteria and toxins. ''Mytilus edulis'' is commonly harvested for food throughout the world, from both wild and farmed sources. Mussels are a staple of many seafood dishes in various cuisines including
Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many Latin American countries **Spanish cuisine Other places * Spanish, Ontario, Can ...
(especially Galician),
Portuguese Portuguese may refer to: * anything of, from, or related to the country and nation of Portugal ** Portuguese cuisine, traditional foods ** Portuguese language, a Romance language *** Portuguese dialects, variants of the Portuguese language ** Portu ...
, French,
Dutch Dutch commonly refers to: * Something of, from, or related to the Netherlands * Dutch people () * Dutch language () Dutch may also refer to: Places * Dutch, West Virginia, a community in the United States * Pennsylvania Dutch Country People E ...
,
Belgian Belgian may refer to: * Something of, or related to, Belgium * Belgians, people from Belgium or of Belgian descent * Languages of Belgium, languages spoken in Belgium, such as Dutch, French, and German *Ancient Belgian language, an extinct languag ...
,
Italian Italian(s) may refer to: * Anything of, from, or related to the people of Italy over the centuries ** Italians, an ethnic group or simply a citizen of the Italian Republic or Italian Kingdom ** Italian language, a Romance language *** Regional Ita ...
and
Turkey Turkey ( tr, Türkiye ), officially the Republic of Türkiye ( tr, Türkiye Cumhuriyeti, links=no ), is a transcontinental country located mainly on the Anatolian Peninsula in Western Asia, with a small portion on the Balkan Peninsula in ...
as midye dolma. They are also commonly used as
lab animals Animals used by laboratories for testing purposes are largely supplied by dealers who specialize in selling them to universities, medical and veterinary schools, and companies that provide contract animal-testing services. It is comparatively rare ...
. Blue mussels were also harvested by the indigenous peoples of North America. Blue mussels are starting to decline in areas such as the Gulf of Maine. Historical references have shown a decrease of about 40 percent in the last fifty years. This can cause a future problem because mussels are foundation species providing homes and protecting other small animals in the intertidal zone like small fish as well as filtering the water. Mussels filter out bacteria, metals, and toxins, that would increase significantly without mussels around.
Ocean acidification Ocean acidification is the reduction in the pH value of the Earth’s ocean. Between 1751 and 2021, the average pH value of the ocean surface has decreased from approximately 8.25 to 8.14. The root cause of ocean acidification is carbon dioxid ...
due to increasing atmospheric carbon dioxide is projected to reduce the growth and survival of blue mussels; in turn, this could drastically reduce their positive impact on coastal water quality.


Gallery

File:Blue mussel Mytilus edulis.jpg, Live blue mussels on a rocky substrate File:Mussels-on-beach-20030601.jpg, Numerous empty blue mussel shells on a beach in
Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its s ...
File:Mytilus edulis (live).jpg, Live blue mussels File:Gegratineerde mosselen.jpg, Mussels and cheese gratin File:Mussel_Sculpture_Conwy_North_Wales_by_Graeme_Mitcheson_photo_6_by_Darren_W_Rees.jpg, Blue mussel sculpture at
Conwy Conwy (, ), previously known in English as Conway, is a walled market town, community and the administrative centre of Conwy County Borough in North Wales. The walled town and castle stand on the west bank of the River Conwy, facing Deganwy on ...
, North Wales near
Conwy Castle Conwy Castle ( cy, Castell Conwy; ) is a fortification in Conwy, located in North Wales. It was built by Edward I, during his conquest of Wales, between 1283 and 1287. Constructed as part of a wider project to create the walled town of Conw ...


References


External links


The blue mussel in Maine
Maine Department of Marine Resources *Newell, R.I.E. (1989)
Species profiles: life histories and environmental requirements of coastal fishes and invertebrates (North and Mid-Atlantic) - blue mussel.
U.S. Fish. Wildl. Serv. Biol. Rep. 82(11. 102 ). U.S. Army Corps of Engineers, TR El-82-4. 25 pp.
The common mussel ''Mytilus edulis''
MarLIN - The Marine Life Information Network *Robert Nordsieck
The Blue or Common Mussel (''Mytilus edulis'')
The Living World of Molluscs www.molluscs.at * {{Authority control Mytilus (bivalve) Commercial molluscs Bivalves described in 1758 Taxa named by Carl Linnaeus Molluscs of the Atlantic Ocean Fauna of the North Sea Seafood in Native American cuisine Marine molluscs of Europe Bivalves of Europe Bivalves of North America