''Modiolus modiolus'', common name northern horsemussel (

Scottish Gaelic Scottish Gaelic ( gd, Gàidhlig ), also known as Scots Gaelic and Gaelic, is a Goidelic language (in the Celtic branch of the Indo-European language family) native to the Gaels of Scotland. As a Goidelic language, Scottish Gaelic, as well as ...

: , Scots: ), 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 ...

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

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 ...

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

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 gen ...

Description

''Modiolus modiolus'' is a large mussel growing to 22 cm (9ins) long though 10 cm (4ins) is a more typical size. The shell is purplish or dark blue and robust, with horny protuberances when young. The two

valves 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 fittings ...

are roughly triangular or bluntly oblong with rounded umbones near the anterior end. The annual growth lines are clear and there is a fine sculpturing of concentric grooves and ridges. The interior of the shell is white with a broad pallial line, large anterior adductor muscle scar and smaller posterior adductor muscle scar. The body is deep orange and the mantle is unfrilled. The shell is firmly attached to the substrate by

byssus 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 (Mytilid ...

threads.Horse mussel - ''Modiolus modiolus''

Marine Life Information Network The Marine Life Information Network (MarLIN) is an information system for marine biodiversity for Great Britain and Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic O ...

. Retrieved 2011-11-01. In

, the species is called 'clabaidh-dubha' ('clabby doos'), meaning 'big black mouths'. More recently in

Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...

the species is commonly known and referred to as 'clappy-doo'. In the

Shetland Shetland, also called the Shetland Islands and formerly Zetland, is a subarctic archipelago in Scotland lying between Orkney, the Faroe Islands and Norway. It is the northernmost region of the United Kingdom. The islands lie about to the no ...

dialect, they are known as "".

Right and left valve of the same specimen: File:Modiolus modiolus 0001.jpg, Right valve File:Modiolus modiolus 0002.jpg, Left valve

Distribution

''M. modiolus'' can be found along the Atlantic coast of North America, from the

Arctic Ocean The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately and is known as the coldest of all the oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, a ...

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

, and along the Pacific coast, from the Arctic Ocean to

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

. It is also found on the European seaboard of the Atlantic Ocean from the United Kingdom northwards. It is found from low tide mark to depths of 50 metres in British waters and 80 metres off the coast of

Nova Scotia Nova Scotia ( ; ; ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. Nova Scotia is Latin for "New Scotland". Most of the population are native Eng ...

. The largest horse mussel bed in Scotland is near Noss Head in Caithness. While it is also found 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 from ...

, it has become a

vulnerable species A vulnerable species is a species which has been Conservation status, categorized by the International Union for Conservation of Nature as being threatened species, threatened with extinction unless the circumstances that are threatened species, ...

there.

Ecology

''M. modiolus'' is found growing on hard substrates including shells and stones and the byssus threads of other mussels. Survival rates of young individuals are low but by the time they reach about 4 cm long, at an age of 4 years, individuals are too large and tough to be predated upon by

starfish 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 ...

such as ''

Asterias rubens The common starfish, common sea star or sugar starfish (''Asterias rubens'') is the most common and familiar starfish in the north-east Atlantic. Belonging to the family Asteriidae, it has five arms and usually grows to between 10–30 ...

'', the whelk ''

Buccinum undatum ''Buccinum undatum'', the common whelk or the waved buccinum, is a large, edible marine gastropod in the family Buccinidae, the "true whelks".Fraussen, K.; Gofas, S. (2014). Buccinum undatum Linnaeus, 1758. Accessed through: World Register of M ...

'' and crabs. Juveniles growing on byssus threads are more likely to survive than free living individuals and this results in the formation of cold-water reefs of mussels.''Modiolus modiolus''
UK Marine SAC's Project. Retrieved 2011-11-01. These mostly occur in locations with fairly strong currents. The species is tolerant of low levels of oxygen and of a diminished quantity of the

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

on which they feed. The boring sponge ''

Cliona celata ''Cliona celata'', occasionally called the boring sponge, is a species of demosponge belonging the family Clionaidae.Hansson, H.G. (Comp.), 1999. NEAT (North East Atlantic Taxa): Scandinavian marine Porifera (Spongiaria) Check- List. Internet pdf ...

'' sometimes damages the shells of older individuals.Comely, C.A., (1978). Modiolus modiolus (L.) from the Scottish West coast. I. Biology. Ophelia, 17, 167-193.

References

External links

{{Taxonbar, from=Q686276 modiolus Molluscs described in 1758 Taxa named by Carl Linnaeus