The scallop is a mollusc, a member of the very large group of animals which include the oyster and the whelk. The scallop belongs to the bivalves, a sub-group which is distinguished by having a pair of shells.
Scallops have a single, large abductor muscle for closing the valves (outer shells). At the edge of the mantle (the soft tissue in contact with most of the valve surface) are short tentacles that hang like a curtain between the valves when they are open. The tentacles detect changes in the composition of the watery medium. Also at the edge of the mantle are eyes. About fifty of these, green ringed with blue are set in the frill, not to show where they are going, since they are always going in the other direction, but to warn them of danger approaching.
Scallops are hermaphrodites with each roe containing the male (whitish testis) and female (orange ovary) sex organs.
The shells are marked with concentric annual rings denoting the age of the scallop - one ring per year.
The king scallop is caught when 10-15cm in diameter, 6-7 years growth - it has a flat upper shell and a convex lower shell.
The queen scallop seldom exceeds 9cm when caught, 2-3 years growth - both of its shells are rounded.
Scallops are most commonly found in a fine sand or shingle sea bed in relatively clear water. They feed on microscopic plants and animals. Cilia (tiny hair-like structures) and mucus aid in the collection and movement of food particles towards the mouth. Scallops are unusual as bivalves in their ability to swim, which they do by spasmodic clapping movements of the valves; water ejected in jet-like spurts, propels the animals forward.
During reproduction eggs and sperm are shed into the water, where fertilization occurs. The eggs develop into free-swimming larvae. In the next developmental stage they settle onto the bottom; some have the ability to crawl. A byssal gland develops and is used to attach the animal firmly to the bottom or to some other solid surface. Some scallops remain attached throughout life; others break free and become spasmodic swimmers.
Scallops are gregarious creatures, they sometimes congregate in thousands of favoured beds of clear, fine sand, and they occur in small numbers anywhere that the bottom is suitable between depths of 60 and 500 feet. The most important predator of scallops is the starfish, which attacks by wrapping its arms about the valves and, by the sucking action of its tube feet, pulls the valves apart; it then inserts its stomach between the valves of the scallop and digests the soft part.
Scallops with their bright orange roes come in highly decorative shells. The fish itself sits in a concave shell and is enclosed by a flat, fan-shaped shell.
In Greek mythology, Aphrodite, the goddess of love and desire, rose from the sea and rode on a scallop shell pulled by six seahorses.
Primitive man ate scallops and used their shells as utensils. Nowadays we still use the concave shell as a serving dish. The majority of cleaned shells we sell are used for this purpose.
The curved scallop shell has become a religious and cultural symbol. The shrine of St. James the apostle at Compostela in Spain has adopted the scallop shell as its emblem and the scallop has been named after the saint - hence Coquilles St. Jacques.
When the body of St. James was being returned to Galicia, borne by boat with 'neither oars, nor sails', it passed a village called Padron, where a wedding was taking place. While frolicking on the sands with his friends, the bridegroom was suddenly dragged into the sea by his panicky horse. Much to everyone's amazement they surfaced beside the ship carrying St. James and his followers. The Christians preached the Gospel to the bridegroom, telling him it was the power of God that had saved him. He promptly converted to Christianity and was baptised. He returned to the shore, where his friends were amazed to see both him and his horse covered in scallop shells.
They all promptly became Christians and the nearby Santiago de Compostela became an important centre of pilgrimage.
The pilgrims would wear scallop-shaped badges as they followed the famous trail to Compostela.