Scallop

A **scallop** is a marine bivalve mollusc of the family **Pectinidae**. Scallops live in all the world's oceans.

This is one of the largest families of living bivalves. There are over 300 living species of scallop.

They have a good reputation as a food source.

The name "scallop" comes from the Old French *escalope*, which means "shell". Their shells can be up to 15 centimetres (6 inches) across.
  The scallop eyes fringing the edge of its shell detect moving objects as they pass successive eyes.

3. Semi-circular ridged shape to the shell. The valves are similar, and fit closely together to make a tight-fitting shell.

4. At some stage in their lives, all scallops all have a ridge of tiny teeth near the notch where the byssus comes out in other bivalves. This is called the *ctenolium*. Its importance is that only scallops have it, and it can be seen in fossils. So that tells palaeontologists when they have a fossil scallop.
 scallop with the left (upper) valve removed]]

## Muscles 
Scallops have a central adductor muscle. This shows where this muscle  to the shell.

The scallop family is unusual because of the variety in arrangements for sexual reproduction. In some species, a scallop has only one sex. They are either male or female. Other species are hermaphrodites so a single scallop has both male and female reproductive organs at the same time. A few scallops are male when they are young and they become female when they grow older.

The Pectinidae family had a large number of species in the Mesozoic era, but they almost disappeared at the end of the Cretaceous period. The survivors evolved rapidly during the Tertiary period. There are nearly 7,000 species and subspecies for the fossil and recent Pectinidae.

## Evolution 
The evolution of bivalves that swim is a consequence of the so-called "Mesozoic marine revolution". In the Mesozoic era sea-floor predators evolved various new forms which fed on the abundant shellfish (brachiopods and bivalves). These predators are still abundant today: they are mostly the starfish, the gastropods, and the crabs.

Each predator has its own methods. Crabs break the shells by force. Some gastropods make holes in the shell and put in a paralysing or relaxing substance; others work on small cracks in the edge of the shell. Once they get their proboscis in, they eat the shellfish.

Starfish are the most common predators. The shells of brachiopods and bivalves are held together by strong muscles. What the starfish does is clamp hold of them on either side with its tube feet, and apply a steady pull. The starfish, with its muscles and hydraulic system, can pull for much longer than any bivalve muscle can withstand. Apparently, ten minutes are usually enough to open the shell a bit. Then the starfish slips its stomach inside the shell. The stomach can get through a slot as narrow as 0.1mm. The starfish then dissolves the mollusc where it lives, absorbing the nutrients.

Consequently, there was a great reproductive advantage for any prey which had even the slightest defence to these predators. Many shellfish developed extra-tough shells. Some burrowed into the sand. Scallops must had had some elementary movement, which developed rapidly under selection.  They became extremely common in the Mesozoic. There are some other methods used by a few scallops. *Chlamys hastata* often carry sponges on their shell. It is a kind of mutualism. The sponge makes it difficult for starfish to get their tube feet on, and camouflages *Chlamys hastata* from predators.

When scallops move off the sand they are open to new predators such as rays, which patrol just above the ocean floor. They may also be picked up by seabirds which open shells by dropping them on rock. Evidently the main advantage lies in getting away from the starfish, which are very numerous on inshore and continental shelf habitats.

### Origins 
Studies have shown the Pectinidae family is monophyletic, developing from a single common ancestor. The direct ancestors of Pectinidae were scallop-like bivalves of the family Entoliidae.

## As food 
### Wild fisheries and aquaculture 
The largest  scallop fishery is for the Atlantic sea scallop (*Placopecten magellanicus*) off northeastern United States and eastern Canada. Most of the rest of the world's production of scallops is from Japan (wild, , and aquaculture), and China (mostly cultured Atlantic bay scallops). In 2005, China accounted for 80% of the global scallop and pecten catch, according to a Food and Agriculture Organization (FAO) study.

### Cooking 
Scallops are popular in both Eastern and Western cooking. They have two types of meat in one shell. The adductor muscle is white and . The roe, called "coral", is red, orange or white and soft. They can also be added to pasta, and are often served as Valentine's day meals. 

The byssus (also called the beard) is often . It is usually discarded or used later on for stock. Sometimes, markets sell scallops already prepared in the shell, with only the adductor muscle.

In Japanese cuisine, scallops may be served in soup or prepared as sashimi or sushi. In a sushi bar, *hotategai* (帆立貝, 海扇) is the traditional scallop on rice. *Kaibashira* (貝柱) might be scallop, but it can also be the adductor muscle of any kind of shellfish, such as mussels, oysters, or clams.
In Cantonese Chinese cuisine dried scallop is called conpoy (乾瑤柱, 乾貝, 干貝).

File:Large scallops.jpg|Adductor muscle meat of the giant scallop
File:BCfood17.JPG|Taiwanese steamed scallops
File:Scallop-Sausages-DSC2415.jpg|A scallop being grilled next to sausages in Japan

## Symbolism 
### Shell of Saint James 
The scallop shell is the traditional emblem of James, son of Zebedee. It is popular with pilgrims on the Way of St James to the apostle's shrine at Santiago de Compostela in Spain.

### Fertility symbol 
]]

Throughout antiquity, scallops and other hinged shells have symbolized the feminine principle. Many paintings of Venus, the Roman goddess of love and fertility, included a scallop shell in the painting to identify her. This is clear in Botticelli's classically inspired *The Birth of Venus*

### Use as a design 
 device on a German coat of arms]]

Heraldry included the scallop shell symbol as a badge for people who had made the pilgrimage to Compostela. Later it became a symbol of pilgrimage in general. Winston Churchill's family coat of arms includes scallops. However, symbols in heraldry do not always have the same meaning. Sometimes no family member has been on a pilgrimage but there are still scallops on the coat of arms.

Over 45 communes of France have one or more scallop shells on their coat of arms.

The U.S. state of New York has had the Atlantic bay scallop as its state shell since 1988. In design, *scalloped edges* or *ridges* means a  pattern which reminds people of the edge of a scallop's shell. Shell petroleum company has had a logo with a scallop shell on it since 1904.

## References 
### Further reading 
* Barucca M. *et al* 2004. Molecular phylogeny of the family Pectinidae (Mollusca: Bivalvia)

## Other websites 
* NOAA Fisheries: Northeast Fisheries Science Center  - Research on Bay Scallop Aquaculture and Enhancement
* 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