Mussel (/ˈmʌsəl/) is the common name used for members of several families of bivalve molluscs, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.
The word "mussel" is frequently used to mean the bivalves of the marine family Mytilidae, most of which live on exposed shores in the intertidal zone, attached by means of their strong byssal threads ("beard") to a firm substrate. A few species (in the genus Bathymodiolus) have colonised hydrothermal vents associated with deep ocean ridges.
In most marine mussels the shell is longer than it is wide, being wedge-shaped or asymmetrical. The external colour of the shell is often dark blue, blackish, or brown, while the interior is silvery and somewhat nacreous.
The common name "mussel" is also used for many freshwater bivalves, including the freshwater pearl mussels. Freshwater mussel species inhabit lakes, ponds, rivers, creeks, canals, and they are classified in a different subclass of bivalves, despite some very superficial similarities in appearance.
Freshwater zebra mussels and their relatives in the family Dreissenidae are not related to previously mentioned groups, even though they resemble many Mytilus species in shape, and live attached to rocks and other hard surfaces in a similar manner, using a byssus. They are classified with the Heterodonta, the taxonomic group which includes most of the bivalves commonly referred to as "clams".
|A bed of blue mussels, Mytilus edulis, in the intertidal zone in Cornwall, England|
The mussel's external shell is composed of two hinged halves or "valves". The valves are joined together on the outside by a ligament, and are closed when necessary by strong internal muscles (anterior and posterior adductor muscles). Mussel shells carry out a variety of functions, including support for soft tissues, protection from predators and protection against desiccation.
The shell has three layers. In the pearly mussels there is an inner iridescent layer of nacre (mother-of-pearl) composed of calcium carbonate, which is continuously secreted by the mantle; the prismatic layer, a middle layer of chalky white crystals of calcium carbonate in a protein matrix; and the periostracum, an outer pigmented layer resembling a skin. The periostracum is composed of a protein called conchin, and its function is to protect the prismatic layer from abrasion and dissolution by acids (especially important in freshwater forms where the decay of leaf materials produces acids).
Like most bivalves, mussels have a large organ called a foot. In freshwater mussels, the foot is large, muscular, and generally hatchet-shaped. It is used to pull the animal through the substrate (typically sand, gravel, or silt) in which it lies partially buried. It does this by repeatedly advancing the foot through the substrate, expanding the end so it serves as an anchor, and then pulling the rest of the animal with its shell forward. It also serves as a fleshy anchor when the animal is stationary.
In marine mussels, the foot is smaller, tongue-like in shape, with a groove on the ventral surface which is continuous with the byssus pit. In this pit, a viscous secretion is exuded, entering the groove and hardening gradually upon contact with sea water. This forms extremely tough, strong, elastic, byssal threads that secure the mussel to its substrate allowing it to remain sessile in areas of high flow. The byssal thread is also sometimes used by mussels as a defensive measure, to tether predatory molluscs, such as dog whelks, that invade mussel beds, immobilising them and thus starving them to death.
In cooking, the byssus of the mussel is known as the "beard" and is removed before the mussels are prepared.
Both marine and freshwater mussels are filter feeders; they feed on plankton and other microscopic sea creatures which are free-floating in seawater. A mussel draws water in through its incurrent siphon. The water is then brought into the branchial chamber by the actions of the cilia located on the gills for ciliary-mucus feeding. The wastewater exits through the excurrent siphon. The labial palps finally funnel the food into the mouth, where digestion begins.
Marine mussels are usually found clumping together on wave-washed rocks, each attached to the rock by its byssus. The clumping habit helps hold the mussels firm against the force of the waves. At low tide mussels in the middle of a clump will undergo less water loss because of water capture by the other mussels.
Both marine and freshwater mussels are gonochoristic, with separate male and female individuals. In marine mussels, fertilization occurs outside the body, with a larval stage that drifts for three weeks to six months, before settling on a hard surface as a young mussel. There, it is capable of moving slowly by means of attaching and detaching byssal threads to attain a better life position.
Freshwater mussels reproduce sexually. Sperm is released by the male directly into the water and enters the female via the incurrent siphon. After fertilization, the eggs develop into a larval stage called a glochidium (plural glochidia), which temporarily parasitizes fish, attaching themselves to the fish's fins or gills. Prior to their release, the glochidia grow in the gills of the female mussel where they are constantly flushed with oxygen-rich water. In some species, release occurs when a fish attempts to attack the mussel's minnow or other mantle flaps shaped like prey; an example of aggressive mimicry.
Glochidia are generally species-specific, and will only live if they find the correct fish host. Once the larval mussels attach to the fish, the fish body reacts to cover them with cells forming a cyst, where the glochidia remain for two to five weeks (depending on temperature). They grow, break free from the host, and drop to the bottom of the water to begin an independent life.
Marine mussels are eaten by humans, starfish, seabirds, and by numerous species of predatory marine gastropods in the family Muricidae, such as the dog whelk, Nucella lapillus. Freshwater mussels are eaten by otters, raccoons, ducks, baboons, humans, and geese.
Marine mussels are abundant in the low and mid intertidal zone in temperate seas globally. Other species of marine mussel live in tropical intertidal areas, but not in the same huge numbers as in temperate zones.
Certain species of marine mussels prefer salt marshes or quiet bays, while others thrive in pounding surf, completely covering wave-washed rocks. Some species have colonized abyssal depths near hydrothermal vents. The South African white mussel exceptionally does not bind itself to rocks but burrows into sandy beaches extending two tubes above the sand surface for ingestion of food and water and exhausting wastes.
Freshwater mussels inhabit permanent lakes, rivers, canals and streams throughout the world except in the polar regions. They require a constant source of cool, clean water. They prefer water with a substantial mineral content, using calcium carbonate to build their shells.
In 2005, China accounted for 40% of the global mussel catch according to a FAO study. Within Europe, where mussels have been cultivated for centuries, Spain remained the industry leader. Aquaculture of mussels in North America began in the 1970s. In the US, the northeast and northwest have significant mussel aquaculture operations, where Mytilus edulis (blue mussel) is most commonly grown. While the mussel industry in the US has increased, in North America, 80% of cultured mussels are produced in Prince Edward Island in Canada. In Washington State, an estimated 2.9M pounds of mussels were harvested in 2010, valued at roughly $4.3M.
Freshwater mussels are used as host animals for the cultivation of freshwater pearls. Some species of marine mussel, including the Blue mussel (Mytilus edulis) and the New Zealand green-lipped mussel (Perna canaliculus), are also cultivated as a source of food.
In some areas of the world, mussel farmers collect naturally occurring marine mussel seed for transfer to more appropriate growing areas, however, most North American mussel farmers rely on hatchery-produced seed. Growers typically purchase seed after it has set (about 1mm in size) or after it has been nursed in upwellers for 3-6 additional weeks and is 2-3mm. The seed is then typically reared in a nursery environment, where it is transferred to a material with a suitable surface for later relocation to the growing area. After about three months in the nursery, mussel seed is "socked" (placed in a tube-like mesh material) and hung on longlines or rafts for grow-out. Within a few days, the mussels migrate to the outside of the sock for better access food sources in the water column. Mussels grow quickly and are usually ready for harvest in less than two years. Unlike other cultured bivalves, mussels use byssus threads (beard) to attach themselves to any firm substrate, which makes them suitable for a number of culture methods.
There are a variety of techniques for growing mussels.
In roughly 12–15 months, mussels reach marketable size (40mm) and are ready for harvest. Harvesting methods depend on the grow-out area and the rearing method being used. Dredges are currently used for on-bottom culture. Mussels grown on wooden poles can be harvested by hand or with a hydraulic powered system. For raft and longline culture, a platform is typically lowered under the mussel lines, which are then cut from the system and brought to the surface and dumped into containers on a nearby vessel. After harvest, mussels are typically placed in seawater tanks to rid them of impurities before marketing.
Additionally byssal threads have provided insight into the construction of artificial tendons.
Mussels are widely used as bio-indicators to monitor the health of aquatic environments in both fresh water and the marine environments. They are particularly useful since they are distributed worldwide and they are sessile. These characteristics ensure that they are representative of the environment where they are sampled or placed. Their population status or structure, physiology, behaviour or the level of contamination with elements or compounds can indicate the status of the ecosystem.
Marine nutrient bioextraction is the practice of farming and harvesting marine organisms such as shellfish and seaweed for the purpose of reducing nutrient pollution. Mussels and other bivalve shellfish consume phytoplankton containing nutrients such as nitrogen (N) and phosphorus (P). On average, one live mussel is 1.0% N and 0.1% P. When the mussels are harvested and removed, these nutrients are also removed from the system and recycled in the form of seafood or mussel biomass, which can be used as an organic fertilizer or animal feed-additive. These ecosystem services provided by mussels are of particular interest to those hoping to mitigate excess anthropogenic marine nutrients, particularly in eutrophic marine systems. While mussel aquaculture is actually promoted in some countries such as Sweden as a water management strategy to address coastal eutrophication, mussel farming as a nutrient mitigation tool is still in its infancy in most parts of the world. Ongoing efforts in the Baltic Sea (Denmark, Sweden, Germany, Poland) and Long Island Sound and Puget Sound in the U.S. are currently examining nutrient uptake, cost-effectiveness, and potential environmental impacts of mussel farming as a means to mitigate excess nutrients and complement traditional wastewater treatment programs.
In the United States and Canada, areas home to the most diverse freshwater mussel fauna in the world, there are 297 known freshwater mussel taxa. Of the 297 known species, 213 (71.7%) taxa are listed as endangered, threatened, of special concern. The main factors contributing to the decline of freshwater mussels include destruction from dams, increased siltation, channel modification, and the introduction of invasive species like the Zebra mussel.
Humans have used mussels as food for thousands of years. About 17 species are edible, of which the most commonly eaten are Mytilus edulis, M. galloprovincialis, M. trossellus and Perna canaliculus.
Nowadays, freshwater mussels are generally considered to be unpalatable and are almost entirely not consumed, although the native peoples of North America ate them extensively and still do today. In the USA during the Second World War, mussels were commonly served in diners and eateries across the country. This was due to the lack of access to red meat (such as beef and pork) for the general public, in relation to the aspect of the American wartime rationing policy concerning food, with much of the meat available being sent to aid the US military's war efforts abroad. Instead, mussels became a popular substitute for most meats (with the exception of chicken).
In Belgium, the Netherlands, and France, mussels are consumed with French fries ("mosselen met friet" or "moules-frites") or bread. In Belgium, mussels are sometimes served with fresh herbs and flavorful vegetables in a stock of butter and white wine. Fries and Belgian beer sometimes are accompaniments. In the Netherlands, mussels are sometimes served fried in batter or breadcrumbs, particularly at take-out food outlets or informal settings. In France, the Éclade des Moules, or, locally, Terré de Moules, is a mussel bake that can be found along the beaches of the Bay of Biscay.
In Italy, mussels are mixed with other sea food, they are consumed often steam cooked (most popular), sometimes with white wine, herbs, and served with the remaining water and some lemon. In Spain, they are consumed mostly steam cooked, sometimes boiling white wine, onion and herbs, and served with the remaining water and some lemon. They can also be eaten as "tigres", a sort of croquette using the mussel meat, shrimps and other pieces of fish in a thick bechamel then breaded and fried in the clean mussel shell. They are used in other sort of dishes such as rices or soups or commonly eaten canned in a pickling brine made of oil, vinegar, peppercorns, bay leaves and paprika.
In Turkey, mussels are either covered with flour and fried on shishs ('midye tava'), or filled with rice and served cold ('midye dolma') and are usually consumed after alcohol (mostly raki or beer).
They are used in Ireland boiled and seasoned with vinegar, with the "bray" or boiling water as a supplementary hot drink.
In Cantonese cuisine, mussels are cooked in a broth of garlic and fermented black bean. In New Zealand, they are served in a chili or garlic-based vinaigrette, processed into fritters and fried, or used as the base for a chowder.
In India, mussels are popular in Kerala, Maharashtra, Karnataka-Bhatkal, and Goa. They are either prepared with drumsticks, breadfruit or other vegetables, or filled with rice and coconut paste with spices and served hot. Fried mussels ('Kadukka' കടുക്ക in Malayalam) of north Kerala especially in Thalassery are a spicy, favored delicacy. In coastal Karnataka Beary's prepare special rice ball stuffed with spicy fried mussels and steamed locally known as "pachilede pindi".
Mussels can be smoked, boiled, steamed, roasted, barbecued or fried in butter or vegetable oil. As with all shellfish, except shrimp, mussels should be checked to ensure they are still alive just before they are cooked; enzymes quickly break down the meat and make them unpalatable or poisonous after dying or uncooked. Some mussels might contain toxins. A simple criterion is that live mussels, when in the air, will shut tightly when disturbed. Open, unresponsive mussels are dead, and must be discarded. Unusually heavy, wild-caught, closed mussels may be discarded as they may contain only mud or sand. (They can be tested by slightly opening the shell halves.) A thorough rinse in water and removal of "the beard" is suggested. Mussel shells usually open when cooked, revealing the cooked soft parts. Historically, it has been believed that after cooking all the mussels should have opened and those that have not are not safe to eat and should be discarded. However, according to marine biologist Nick Ruello, this advice may have arisen from an old, poorly researched cookbook's advice, which has now become an assumed truism for all shellfish. Ruello found 11.5% of all mussels failed to open during cooking, but when forced open, 100% were "both adequately cooked and safe to eat."
Although mussels are valued as food, mussel poisoning due to toxic planktonic organisms can be a danger along some coastlines. For instance, mussels should be avoided along the west coast of the United States during the warmer months. This poisoning is usually due to a bloom of dinoflagellates (red tides), which contain toxins. The dinoflagellates and their toxin are harmless to mussels, even when concentrated by the mussel's filter feeding, but if the mussels are consumed by humans, the concentrated toxins cause serious illness, such as paralytic shellfish poisoning. A person affected in this way after eating mussels is said to be musselled.
|Serving size||3 ounces (85 g)|
|Total fat||1.9 g|
|Saturated fat||0.4 g|
Foods that are an "excellent source" of a particular nutrient provide 20% or more of the recommended daily value. Foods that are a "good source" of a particular nutrient provide between 10 and 20% of the recommended daily value.
The blue mussel (Mytilus edulis), also known as the common mussel, is a medium-sized edible marine bivalve mollusc in the family Mytilidae, the mussels. Blue mussels are subject to commercial use and intensive aquaculture.Byssus
A byssus is a bundle of filaments secreted by many species of bivalve mollusk that function to attach the mollusk to a solid surface. Species from several families of clams have a byssus, including the pen shells, the true mussels and the false mussels: the Pinnidae, the Mytilidae and the Dreissenidae.
Byssus cloth is a rare fabric, also known as sea silk, that is made using the byssus of pen shells as the fiber source.California mussel
The California mussel (Mytilus californianus) is a large edible mussel, a marine bivalve mollusk in the family Mytilidae.
This species is native to the west coast of North America, occurring from northern Mexico to the Aleutian Islands of Alaska. California mussels are found clustered together, often in very large aggregations, on rocks in the upper intertidal zone on the open coast, where they are exposed to the strong action of the surf.Freshwater bivalve
Freshwater bivalves are one kind of freshwater molluscs, along with freshwater snails. They are bivalves which live in freshwater, as opposed to saltwater, the main habitat type for bivalves.
The majority of species of bivalve molluscs live in the sea, but in addition, a number of different families live in freshwater (and in some cases also in brackish water). These families belong to two different evolutionary lineages (freshwater mussels and freshwater clams), and the two groups are not closely related.
Freshwater bivalves live in many types of habitat, ranging from small ditches and ponds, to lakes, canals, rivers, and swamps.
Species in the two groups vary greatly in size. Some of the pea clams (Pisidium species) have an adult size of only 3 mm. In contrast, one of the largest species of freshwater bivalves is the swan mussel, in the family Unionidae; it can grow to a length of 20 cm, and usually lives in lakes or slow rivers.
Freshwater pearl mussels are economically important as a source of freshwater pearls and mother of pearl.Freshwater pearl mussel
The freshwater pearl mussel (Margaritifera margaritifera) is an endangered species of freshwater mussel, an aquatic bivalve mollusc in the family Margaritiferidae.
Although the name "freshwater pearl mussel" is often used for this species, other freshwater mussel species can also create pearls and some can also be used as a source of mother of pearl. In fact, most cultured pearls today come from Hyriopsis species in Asia, or Amblema species in North America, both members of the related family Unionidae; pearls are also found within species in the genus Unio.
The interior of the shell of Margaritifera margaritifera has thick nacre (the inner mother of pearl layer of the shell). This species is capable of making fine-quality pearls, and was historically exploited in the search for pearls from wild sources. In recent times, the Russian malacologist Valeriy Zyuganov received worldwide reputation after he discovered that the pearl mussel exhibited negligible senescence and he determined that it had a maximum lifespan of 210–250 years. The data of V.V. Zyuganov have been confirmed by Finnish malacologists and gained general acceptance.Lithophaga
Lithophaga, the date mussels, are a genus of medium-sized marine bivalve molluscs in the family Mytilidae. Some of the earliest fossil Lithophaga shells have been found in Mesozoic rocks from the Alps and from Vancouver Island,The shells of species in this genus are long and narrow with parallel sides. The animals bore into stone or coral rock with the help of pallial gland secretions, hence the systematic name Lithophaga, which means "stone-eater". Their club-shaped borings are given the trace fossil name Gastrochaenolites.Mediterranean mussel
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.Mussel Shoals, California
Mussel Shoals is a coastal unincorporated community in Ventura County, California, between Ventura and the Santa Barbara County city of Carpinteria.
The community lies along U.S. Route 101 southeast of La Conchita and northwest of
Faria. A one-lane causeway links the community with artificial Rincon Island.
Until the 1930s, the area from Bates Road down to Mussel Shoals (then known as Mussel Rock) was referred to as La Conchita.Mussel Slough Tragedy
The Mussel Slough Tragedy was a dispute over land titles between settlers and the Southern Pacific Railroad (SP) that took place on May 11, 1880, on a farm located 5.6 miles (9 km) northwest of Hanford, California, in the central San Joaquin Valley, leaving seven people dead. Frank Norris' 1901 novel, The Octopus: A Story of California, was inspired by this incident, as was W. C. Morrow's 1882 novel Blood-Money. May Merrill Miller's novel, First the Blade, includes a fictionalized account of the conflict. The exact history of the incident has been the source of some disagreement, largely because popular anti-railroad sentiment in the 1880s made the incident to be a clear example of corrupt and cold-blooded corporate greed. Muckraking journalists and anti-railroad activists glorified the settlers and used the events as evidence and justification for their anti-corporate crusades. The site of the episode is now registered as California Historical Landmark #245. A historical marker on the east side of 14th Avenue, 350 yards (320 m) north of Elder Avenue, memorializes the site.Mytilidae
The Mytilidae are a family of small to large saltwater mussels, marine bivalve mollusks in the order Mytiloida. One of the genera, Limnoperna, inhabits brackish or freshwater environments. The order has only this one family which contains some 52 genera.Species in the family Mytilidae are found worldwide, but they are more abundant in colder seas, where they often form uninterrupted beds on rocky shores in the intertidal zone and the shallow subtidal. The subfamily Bathymodiolinae is found in deep-sea habitats.
Mytilids include the well-known edible sea mussels.
A common feature of the shells of mussels is an asymmetrical shell which has a thick, adherent periostracum. The animals attach themselves to a solid substrate using a byssus.Ostracod
Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typically around 1 mm (0.039 in) in size, but varying from 0.2 to 30 mm (0.008 to 1.181 in) in the case of Gigantocypris. Their bodies are flattened from side to side and protected by a bivalve-like, chitinous or calcareous valve or "shell". The hinge of the two valves is in the upper (dorsal) region of the body. Ostracods are grouped together based on gross morphology. While early work indicated the group may not be monophyletic; and early molecular phylogeny was ambiguous on this front, recent combined analyses of molecular and morphological data found support for monophyly in analyses with broadest taxon sampling Ecologically, marine ostracods can be part of the zooplankton or (most commonly) are part of the benthos, living on or inside the upper layer of the sea floor. Many ostracods, especially the Podocopida, are also found in fresh water, and terrestrial species of Mesocypris are known from humid forest soils of South Africa, Australia and New Zealand. They have a wide range of diets, and the group includes carnivores, herbivores, scavengers and filter feeders.
As of 2008, around 2000 species and 200 genera of nonmarine ostracods are found. However, a large portion of diversity is still undescribed, indicated by undocumented diversity hotspots of temporary habitats in Africa and Australia. Of the known specific and generic diversity of nonmarine ostracods, half (1000 species, 100 genera) belongs to one family (of 13 families), Cyprididae. Many Cyprididae occur in temporary water bodies and have drought-resistant eggs, mixed/parthenogenetic reproduction, and the ability to swim. These biological attributes preadapt them to form successful radiations in these habitats.Oyster omelette
The oyster omelette (Chinese: 蚵仔煎; Pe̍h-ōe-jī: ô-á-chian) is a dish of Teochew origin that is widely known for its savoury taste in its native Chaoshan along with Fujian, Taiwan, and many parts of Southeast Asia such as the Philippines and Thailand due to the influence of the Teochew diaspora. Variations of the dish preside in some southern regions of China.
In Thailand it was adapted to Mussel omelettes; most Thai people have the misconception that oyster omelettes and mussel omelettes originated from Thai cuisine rather than Chinese. In Bangkok, notable areas for oyster omelettes include Talat Wang Lang near Siriraj Hospital; Wang Lang (Siriraj) Pier in Bangkok Noi where there are two restaurants; Yaowarat neighborhood, where there is one Michelin-Bib Gourmand restaurant with Charoen Krung neighborhood in Bang Rak, among others. In 2017, the World Street Food Congress announced that oyster omelette is one of the three most notable street food among the street foods of Thailand.The oyster omelette is a Taiwanese "night market favorite", and has constantly been ranked by many foreigners as the top dish from Taiwan. Its generous proportions and affordable price demonstrates the trait of night market cuisines.Perna canaliculus
The New Zealand green-lipped mussel (Perna canaliculus), also known as the New Zealand mussel, the greenshell mussel, kuku, and kutai, is a bivalve mollusc in the family Mytilidae (the true mussels). P. canaliculus has economic importance as a cultivated species in New Zealand.Perna perna
Perna perna (brown mussel) is an economically important mussel, a bivalve mollusc belonging to the family Mytilidae. It is harvested as a food source but is also known to harbor toxins and cause damage to marine structures. It is native to the waters of Africa, Europe, and South America and was introduced in the waters of North America.Perna viridis
Perna viridis, known as the Asian green mussel, is an economically important mussel, a bivalve belonging to the family Mytilidae. It is harvested for food but is also known to harbor toxins and cause damage to submerged structures such as drainage pipes. It is native in the Asia-Pacific region but has been introduced in the Caribbean, and in the waters around Japan, North America, and South America.Short Mussel
The Short S.7 Mussel was a single-engined two-seat monoplane built by Short Brothers to test the performance of their duralumin monocoque floats. Two were built.Unionidae
The Unionidae are a family of freshwater mussels, the largest in the order Unionoida, the bivalve mollusks sometimes known as river mussels, or simply as unionids.The range of distribution for this family is world-wide. It is at its most diverse in North America, with about 297 recognised taxa, but China and Southeast Asia also support very diverse faunas.
Freshwater mussels occupy a wide range of habitats, but most often occupy lotic waters, i.e. flowing water such as rivers, streams and creeks.Unionoida
Unionoida is a monophyletic order of freshwater mussels, aquatic bivalve molluscs. The order includes most of the larger freshwater mussels, including the freshwater pearl mussels. The most common families are the Unionidae and the Margaritiferidae. All have in common a larval stage that is temporarily parasitic on fish, nacreous shells, high in organic matter, that may crack upon drying out, and siphons too short to permit the animal to live deeply buried in sediment.Zebra mussel
The zebra mussel (Dreissena polymorpha) is a small freshwater mussel. This species was originally native to the lakes of southern Russia and Ukraine. However, the zebra mussel has been accidentally introduced to numerous other areas, and has become an invasive species in many countries worldwide. Since the 1980s, they have invaded the Great Lakes and the Hudson River.
The species was first described in 1769 by the German zoologist Peter Simon Pallas in the Ural, Volga, and Dnieper rivers. Zebra mussels get their name from a striped pattern commonly seen on their shells, though it is not universally present. They are usually about the size of a fingernail, but can grow to a maximum length of nearly 2 in (5.1 cm). Shells are D-shaped, and attached to the substrate with strong byssal fibers, which come out of their umbo on the dorsal (hinged) side.
|Land and freshwater gastropods|
|Free-swimming marine bivalves|
Principal commercial fishery species groups