However, as many scallop shells are more or less bilaterally symmetrical ("equivalved"), as well as symmetrical front/back ("equilateral"), determining which way a given animal is "facing" requires detailed information about its valves. With the hinge of the two valves oriented towards the top, one side corresponds to the animal's morphological anterior or front, the other is the posterior or rear, the hinge is the dorsal or back/top region, and the bottom corresponds to the ventral or (as it were) underside/belly. Most species of scallops rest on their right valve, and consequently this valve is often deeper and more rounded than the left (i.e., upper) valve, which in many species is actually concave. The shell of a scallop consists of two sides or valves, a left valve and a right one, divided by a plane of symmetry. Orientation Īnatomical diagram of an Atlantic bay scallop with the left (i.e., upper) valve removed anterior is to the left, posterior to the right Very little variation occurs in the internal arrangement of organs and systems within the scallop family, and what follows can be taken to apply to the anatomy of any given scallop species.
Most scallops begin their lives as byssally attached juveniles, an ability that some retain throughout their lives while others grow into freeliving adults. Scallops can be found living within, upon, or under either rocks, coral, rubble, sea grass, kelp, sand, or mud. Although some species only live in very narrow environments, most are opportunistic and can live under a wide variety of conditions. Most species live in relatively shallow waters from the low tide line to 100 m, while others prefer much deeper water. Scallops inhabit all the oceans of the world, with the largest number of species living in the Indo-Pacific region.
The shells also have a significant place in popular culture, including symbolism.īiology Distribution and habitat Owing to their widespread distribution, scallop shells are a common sight on beaches and are often brightly coloured, making them a popular object to collect among beachcombers and vacationers. The brightly coloured, symmetric, fan-shaped shells of scallops with their radiating and often fluted ornamentation are valued by shell collectors, and have been used since ancient times as motifs in art, architecture, and design. The word "scallop" is also applied to the meat of these bivalves, the adductor muscle, that is sold as seafood. Many species of scallops are highly prized as a food source, and some are farmed as aquaculture.
Scallops have a well-developed nervous system, and unlike most other bivalves all scallops have a ring of numerous simple eyes situated around the edge of their mantles. The majority of species, however, live recumbent on sandy substrates, and when they sense the presence of a predator such as a starfish, they may attempt to escape by swimming swiftly but erratically through the water using jet propulsion created by repeatedly clapping their shells together. A small minority of scallop species live cemented to rocky substrates as adults, while others attach themselves to stationary or rooted objects such as sea grass at some point in their lives by means of a filament they secrete called a byssal thread. They are one of very few groups of bivalves to be primarily "free-living", with many species capable of rapidly swimming short distances and even of migrating some distance across the ocean floor. Scallops are a cosmopolitan family of bivalves which are found in all of the world's oceans, although never in fresh water. However, the common name "scallop" is also sometimes applied to species in other closely related families within the superfamily Pectinoidea, which also includes the thorny oysters. Scallop ( / ˈ s k ɒ l ə p, ˈ s k æ l ə p/) is a common name that is primarily applied to any one of numerous species of saltwater clams or marine bivalve mollusks in the taxonomic family Pectinidae, the scallops. Argopecten irradians, the Atlantic bay scallop