A scallop ( or ) is a marine bivalve mollusc of the family Pectinidae. Scallops are a cosmopolitan family, found in all of the world's oceans. Many scallops are highly prized as a food source. The brightly colored, fan-shaped shells of some scallops, with their radiating fluted pattern, are valued by shell collectors.

The name "scallop" is derived from the Old French ''escalope'', which means "shell".

Anatomy

Like the true oysters (family Ostreidae), scallops have a central adductor muscle, and thus the inside of their shells has a characteristic central scar, marking the point of attachment for this muscle. The adductor muscle of scallops is larger and more developed than that of oysters, because they are active swimmers; scallops are in fact the only migratory bivalve. Their shell shape tends to be highly regular, recalling one archetypal form of a seashell, and because of this pleasing geometric shape, the scallop shell is a common decorative motif.

Scallops have up to 100 simple eyes strung around the edges of their mantles like a string of beads. They are reflector eyes, about one mm in diameter, with a retina that is more complex than those of other bivalves. Their eyes contain two retina types, one responding to light and the other to abrupt darkness, such as the shadow of a nearby predator. They cannot resolve shapes, but can detect changing patterns of light and motion.

Reflector eyes are an alternative to a lens where the inside of the eye is lined with mirrors which reflect the image to focus at a central point. The nature of these eyes means that if one were to peer into the pupil of an eye, one would see the same image that the organism would see, reflected back out. The scallop ''Pecten'' has up to 100 millimeter-scale reflector eyes fringing the edge of its shell. It detects moving objects as they pass successive lenses.

Food and digestion

Most scallops are filter feeders, and eat plankton. Coincidentally, the plankton can include scallop larvae. Siphons bring water over a filtering structure, where food becomes trapped in mucus. Next, the cilia on the structure move the food toward the mouth. Then, the food is digested in the stomach and digestive gland. Waste is passed on through the intestine and exits via the anus.

Life habits

Most scallops are free-living, but some species can attach to a substrate by a structure called a byssus, or even be cemented to their substrate as adults (e.g. ''Hinnites spp.''). Other scallops can extend a "foot" from between their valves (shell). By then contracting the foot, they can burrow themselves deeper into sand. A free-living scallop can swim by rapidly opening and closing its shell. This method of locomotion is also a defensive technique, protecting it from threatening predators. So-called Singing Scallops can make an audible soft popping sound as they flap their shells underwater.

Reproductive cycle

The scallop family is unusual in that some members of the family are dioecious (males and females are separate), while other are simultaneous hermaphrodites (both sexes in the same individual) and a few are protoandrous hermaphrodites (males when young then switching to female). Red roe is that of a female, and white, that of a male. Spermatozoa and ova are released freely into the water during mating season and fertilized ova sink to the bottom. After several weeks, the immature scallop hatches and the larvae drift in the plankton until settling to the bottom again to grow, usually attaching by means of byssal threads. Some scallops, such as the Atlantic bay scallop ''Argopecten irradians'' are short lived, while others can live 20 years or more. Age can often be inferred from annuli, the concentric rings of their shells.

Seafood industry

Wild fisheries

By far the largest wild scallop fishery is for the Atlantic sea scallop (''Placopecten magellanicus'') found off northeastern United States and eastern Canada. Most of the rest of the world's production of scallops is from Japan (wild, enhanced, and aquaculture), and China (mostly cultured Atlantic bay scallops).

Scallops are most commonly harvested using scallop dredges or bottom trawls. Recently, scallops harvested by divers, hand-caught on the ocean floor, have entered the marketplace. In contrast to scallops captured by a dredge across the sea floor, diver scallops tend to be less gritty. They may also be more ecologically friendly, as the harvesting method does not cause damage to undersea flora or fauna. In addition, dredge-harvesting methods often result in delays of up to two weeks before the scallops arrive at market, which can cause the flesh to break down, and results in a much shorter shelf life.

Aquaculture

In 2005, China accounted for 80 percent of the global scallop and pecten catch, according to an FAO study. Within Europe, Russia remained the industry leader.

Sustainability

;New Zealand The Tasman Bay area has been closed to commercial scallop harvesting for the past two years due to a decline in the numbers. Industry-funded research is currently being conducted into scallop harvesting patterns. Forest and Bird list scallops as "Worst Choice" in their Best Fish Guide for sustainable seafood species.

;United States On the east coast of the United States, over the last 100 years, the populations of bay scallops have greatly diminished. This decrease is due to several factors, but probably is mostly due to reduction in sea grasses (to which bay scallop spat attach) due to increased coastal development and concomitant nutrient runoff. Another possible factor is reduction of sharks from overfishing. A variety of sharks used to feed on rays, which are a main predator of bay scallops. With the shark population reduced—in some places almost eliminated—the rays have been free to dine on scallops to the point of greatly decreasing their numbers. By contrast, the Atlantic sea scallop (''Placopecten magellanicus'') is at historically high levels of abundance after recovery from overfishing.

As food

Scallops are a popular type of shellfish in both Eastern and Western cooking. They are characterized by having two types of meat in one shell: the adductor muscle, called "scallop" which is white and meaty, and the roe, called "coral", which is red or white and soft.

In Western cuisine, scallops are commonly sautéed in butter, or else breaded and deep fried. When a scallop is prepared, the byssus, also called the beard, which tends to be tough, is usually discarded or used later on for stock. Sometimes, markets sell scallops already prepared in the shell, with only the adductor muscle intact. Outside the U.S. the scallop is often sold whole.

Scallops that are without any additives are called "dry packed", while scallops that are treated with sodium tripolyphosphate (STPP) are called "wet packed". STPP causes the scallops to absorb moisture prior to the freezing process, thereby getting a better price per unit of weight. The freezing process takes about two days.

In Japanese cuisine, scallops may be served in soup or prepared as sashimi or sushi. Dried scallop is known in Cantonese Chinese cuisine as conpoy (乾瑤柱, 乾貝, 干貝).

In a sushi bar, ''hotategai'' (帆立貝, 海扇) is the traditional scallop on rice, and while ''kaibashira'' (貝柱) may be called scallops, it is actually the adductor muscle of any kind of shellfish, e.g. mussels, oysters, or clams.

Scallops have lent their name to the culinary term ''scalloped'', which originally referred to seafood creamed and served hot in the shell (Rombauer 1964). Today it means a creamed casserole dish such as scalloped potatoes, which contains no seafood at all.

Symbolism

=== Shell of Saint James === The scallop shell is the traditional emblem of James, son of Zebedee and is popular with pilgrims on the Way of St James to the apostle's shrine at Santiago de Compostela in Spain. Medieval Christians making the pilgrimage to his shrine often wore a scallop shell symbol on their hat or clothes. The pilgrim also carried a scallop shell with him, and would present himself at churches, castles, abbeys etc., where he could expect to be given as much sustenance as he could pick up with one scoop. Probably he would be given oats, barley, and perhaps beer or wine. Thus even the poorest household could give charity without being overburdened. The association of Saint James with the scallop can most likely be traced to the legend that the apostle once rescued a knight covered in scallops. An alternative version of the legend holds that while St. James' remains were being transported to Spain from Jerusalem, the horse of a knight fell into the water, and emerged covered in the shells.

Fertility symbol

Throughout antiquity, scallops and other hinged shells have symbolized the feminine principle. Outwardly the shell can symbolize the protective and nurturing principle, and inwardly the "life-force slumbering within the Earth", an emblem of the vulva.

Many paintings of Venus, the Roman goddess of love and fertility, included a scallop shell in the painting to identify her. This is evident in Botticelli's classically inspired ''The Birth of Venus'' (also known as ''Venus on the half-shell'').

One legend of the Way of St. James holds that the route was seen as a sort of fertility pilgrimage, undertaken when a young couple desired to bear offspring. The scallop shell is believed to have originally been carried therefore by pagans as a symbol of fertility.

Alternatively, the scallop resembles the setting sun, which was the focus of the pre-Christian Celtic rituals of the area. To wit, the pre-Christian roots of the ''Way of St. James'' was a Celtic death journey westwards towards the setting sun, terminating at the ''End of the World'' (''Finisterra'') on the "Coast of Death" (Costa da Morte) and the "Sea of Darkness" (i.e., the Abyss of Death, the ''Mare Tenebrosum'', Latin for the Atlantic Ocean, itself named after the ''Dying Civilization'' of Atlantis). The reference to St. James rescuing a "knight covered in scallops" is therefore a reference to St. James healing, or resurrecting, a dying (setting sun) knight. Similarly, the notion of the "Sea of Darkness" (Atlantic Ocean) disgorging St. James' body, so that his relics are (allegedly) buried at Santiago de Compostella on the coast, is itself a metaphor for "rising up out of Death", that is, resurrection.

Heraldry

The scallop shell symbol found its way into heraldry as a badge of those who had been on the pilgrimage to Compostela, although later it became a symbol of pilgrimage in general. Winston Churchill's family coat of arms includes a scallop; another example is the surname Wilmot and also John Wesley's (which as a result the scallop shell is used as an emblem of Methodism). However, charges in heraldry do not always have an unvarying symbolic meaning, and there are cases of arms in which no family member went on a pilgrimage and the occurrence of the scallop is simply a pun on the name of the armiger, or for other reasons.

State shell of New York

The U.S. state of New York made the Atlantic bay scallop its state shell in 1988.

In design

In design, ''scalloped edges'' or ''ridges'' refers to a wavy pattern reminiscent of the edge of a scallop's shell.

References

Barucca M, Olmo E, Schiaparelli S, Canapa A (2004) Molecular phylogeny of the family Pectinidae (Mollusca: Bivalvia)

Rombauer, Irma S. and Marion Rombauer Becker (1931 [1964]) ''The Joy of Cooking'', p 369. Indianapolis: Bobbs-Merrill. ISBN 0-452-25665-8.

External links

Alaska Department of Fish and Game - scallop page

NOAA Fisheries: Northeast Fisheries Science Center - Research on Bay Scallop Aquaculture and Enhancement

Delaware Sea Grant, University of Delaware - scallop page

Classification of Pectinoidea (Propeamussiidae and Pectinidae) - includes partly different genera, with subfamilies and tribes.

"Too Few Jaws: Shark declines let rays overgraze scallops", ''Science News'', March 31, 2007

Category:Aquaculture Category:Bivalves Category:Commercial molluscs Category:Edible molluscs Category:Pectinidae Category:State shells of the United States

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