After fertilization, P. magellanicus develop into a ciliated larva known as the trochosphere. At this stage, they have cilia near their tops and also have a cilia ring around their middle. Then, the larvae quickly mature to veligers. These planktotrophic larvae are ciliary feeders and float in plankton fields for approximately two or three months. The larvae continue to develop and begin to secrete two valves from their mantle cavity as they reach adulthood. During the first several years of life, scallops rapidly increase in size and bulk. The third to fifth year has the most growth. They increase shell height by fifty to eighty percent and quadruple in body weight. Once adult scallops, they become free swimming.
Development - Life Cycle: metamorphosis
Deep sea scallops are predominantly used in cuisine. The scallop's valves are removed and the soft adductor muscles are consumed in many dishes around the world. The shells hold an artistic appeal and are bought by thousands of tourists visiting the Northern Coast. Indians continue to use the convex shells as plates.
Positive Impacts: food
P. magellanicus play a critical role in their ecosystems. While feeding, they recycle incredible amounts of organic material and filter harmful bacteria from the water. They also aid in purifying polluted water.
The deep sea scallop's ctenidia and labial cilia serve as instruments for food collection. There is a ventral and dorsal siphon. Water enters the ventral siphon and a current is maintained to pass through the gill lamellae. Here, the scallop separates food particles from mud and sand according to size. The ctnedia then transport the food particles to the mantle cavity and circulate over many groups of cilia. The particles become covered with mucus and are pushed either toward the mouth or the rejection path, which leaves through the dorsal siphon. The mucus covered food is then carried to the stomach through the esophagus, but first passes through the crystalline style, a gelantinous rotating rod. Here, the food is digested in intracellular food vacoules and waste is removed through the intestines and out through the anus.
Foods eaten include microscopic plants, bacteria and organic particles.
Plant Foods: algae; phytoplankton
Other Foods: detritus ; microbes
Foraging Behavior: filter-feeding
Primary Diet: herbivore (Algivore); planktivore ; detritivore
Placopecten magellanicus, Deep Sea Scallops, are native to the Atlanic Ocean and range from Labrador to North Carolina. Labrador is located very near New Foundland on the Eastern coast of Canada. They have now become more dispersed throughout this area as a result of farmers introducing them to varying locations in order to breed them for culinary purposes, but the majority remain in the Northern Atlantic Ocean.
Biogeographic Regions: nearctic (Native ); atlantic ocean (Native )
Placopecten magellanicus live in moderately deep water. Populations north of Cape Cod live in shallow water, approximately twenty meters. South of Cape Cod, populations live in deeper water ranging from forty to two-hundred meters. They can only survive in marine environments and prefer the cool water of the Northern Atlantic, which stays around sixty-eight degrees Fahrenheit. While resting, they lie on the sand or mud of the ocean bottom.
Range depth: 20 to 200 m.
Average depth: 40 m.
Habitat Regions: temperate ; saltwater or marine
Aquatic Biomes: pelagic ; coastal
Deep sea scallops reach full adulthood at four years of age and tend to live several years afterward. On average, they live for approximately six to eight years.
Typical lifespan
Status: wild: 6 to 8 years.
Deep sea scallops secrete two vavles, which are large, thick, and oval-shaped. This shell is often greater in height than width. The valves are unequal in size, with the lower being almost flat and the upper being convex. Grooves radiate from the hinge towards the shell edge. The upper valve is dark in color, usually red or pinkish brown and sometimes rayed with white, while the lower is lighter and is pinkish white. The shell's inside is a glossy white with a distinctive muscular scar where the soft body attaches. The muscle itself is white or tan in color and has two labial or feeding palps with a mouth in between. The scallop's body is wedge-shaped with a ventrally located foot. The gills or ctenidia are in the mantle cavity and are commonly enlarged and have a complex arrangement. A row of eyes peaks from in between the the valves and are attached to the mantle cavity.
Range length: 10 to 23 cm.
Average length: 15 cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry ; polymorphic
Even though deep sea scallops have a high concentration of sensory organs near the edge of the mantle cavity, they only have a relatively simple nervous system. Visceral ganglia near the optic lobes fuse with other ganglia to form a simplistic "visceral brain", which constitutes most of the scallop's nervous system. The concentration of sensory organs allow the scallop to be aware of its surroundings at all times. Most prominent and useful are their row of eyes between the two vavles, which aid in watching for predators. The eyes are usually coblat blue in color and are located on the tip of pallial tentacles. Although their eyes are complete with cornea and lens, they are unable to discern shapes. They can only detect changes in light and movement and react to flashing lights or stripes that move at particular speeds, which resemble speeds of their predators, starfish and whelks. The chemical sensitive pallial tentacles are also able to react to excretions of starfish. When a predator is spotted or the scallop is touched, the scallop quickly propels itself from danger. They can do this by rapidly clapping their two valves together and moving in jerks or darts. Movement occurs through a type of jet propulsion. A jet of water is forced backwards and out through the wings and hinge. The locomotion is mainly powered by the large muscle known as the body or mantle cavity.
Known Predators:
Deep sea scallops respond to sight and touch. The scallops' eyes are very developed with corneas and lenses, which serves as their dominant means of interaction. The only time they communicate with other scallops is during reproduction. The sperm stimulate the release of eggs.
Communication Channels: visual ; tactile
Other Communication Modes: photic/bioluminescent ; pheromones
Perception Channels: visual ; tactile ; chemical
Instead of releasing eggs and sperm randomly, scallops stimulate one another to spawn at the same time. The sperm is released first and then enters the food current of other scallops, which causes them to release eggs into the mantle cavity.
By the age of two, P. magellanicus are sexually mature, but do not actively produce eggs until four. The majority of deep sea scallops undergo multiple sex changes during their lifetime. They are known as functionally ambisexual and shelter the ova and sperm in the same gonad, but the two are produced in different areas of the gonad. About four percent are hermaphrodites and carry both an ovary and testis within the mantle cavity. The ovary is a very bright pink when carrying ripe eggs and the cream colored testis lie behind the ovary. The two are fused together and have short ducts with no glands. Eggs are not released in the water, but wait for the sperm in the mantle cavity. Fertilization occurs when the sperm usually meet the eggs near the opening of the mantle cavity. Then, the scallops immediately release the zygotes into the water.
Breeding season: Late Summer and early Fall, but can also occur in Spring within populations living in the Mid-Atlantic region
Range age at sexual or reproductive maturity (female): 2 (low) years.
Range age at sexual or reproductive maturity (male): Two (low) years.
Key Reproductive Features: year-round breeding ; simultaneous hermaphrodite; sexual ; fertilization (Internal )
Because Deep Sea Scallops create so many sperm and eggs to ensure numerous offspring, they do not have the energy to take care of the offspring. Also, external fertilization does not allow the parents to keep track of their offspring. They produce too many offspring to differentiate between their own and the hundreds of other offspring in the area.
Parental Investment: pre-fertilization (Provisioning)
Placopecten magellanicus, previously listed as Pecten tenuicostatus and as Pecten grandis[2] and once referred to as the "giant scallop", common names Atlantic deep-sea scallop, deep sea scallop, North Atlantic sea scallop, American sea scallop, Atlantic sea scallop, or sea scallop,[3] is a commercially important pectinid bivalve mollusk native to the northwest Atlantic Ocean.[4]
The shell has a classic form, with smooth shell and edges, unlike Pecten maximus (common name the "great scallop" or "king scallop") which has flutes and scalloped edges; size is around 80 millimetres (3+1⁄4 in), with individuals up to 170 millimetres (6+3⁄4 in) in diameter. The shell is generally pinkish-red in color, with striped variegation to darker shades appearing in many individuals. The adductor muscle itself is large, often 30–40 millimetres (1+1⁄4–1+1⁄2 in) in diameter. Like all scallops, P. magellanicus has photoreceptive eyes along the edge of the pinkish mantle.[5]
Placopecten magellanicus is found on the continental shelf of the northwest Atlantic from the north shore of the Gulf of St. Lawrence south to Cape Hatteras, North Carolina.[6]
Sea scallops typically occur at depths ranging from 18–110 m, but may also occur in waters as shallow as 2 m in estuaries and embayments along the Maine coast and in Canada. In southern areas, scallops are primarily found at depths between 45 and 75 m, and are less common in shallower water (25–45 m) due to high temperature. Although sea scallops are not common at depths greater than about 110 m, some populations have been found as deep as 384 m, and deep-water populations at 170–180 m have been reported in the Gulf of Maine. Sea scallops often occur in aggregations called beds. Beds may be sporadic (perhaps lasting for a few years) or essentially permanent (e.g., commercial beds supporting the Georges Bank fishery). The highest concentration of many permanent beds appears to correspond to areas of suitable temperatures, food availability, substrate, and where physical oceanographic features such as fronts and gyres may keep larval stages in the vicinity of the spawning population.[6]
Adult sea scallops are generally found on firm sand, gravel, shells, and rock. Other invertebrates associated with scallop beds include sponges, hydroids, anemones, bryozoans, polychaetes, mussels, moon snails, whelks, amphipods, crabs, lobsters, sea stars, sea cucumbers, and tunicates.[6]
According to NOAA, the Atlantic sea scallop fishery is healthy, and is harvested at sustainable levels.[7] The federal fishery is managed by NOAA Fisheries and the New England Fishery Management Council. The U.S. Atlantic sea scallop fishery is the largest wild scallop fishery in the world.[8] In 2008, 53.5 million pounds of sea scallop meats worth $370 million were harvested in the United States, with Massachusetts and New Jersey responsible for the majority.[9] In 2018, 58.2 million pounds of sea scallop meats worth $532.9 million were harvested in the United States with Massachusetts responsible for the majority.[10]
Between the 1960s and the mid-1990s, the U.S. federal Atlantic sea scallop fishery declined steadily. In 1994 a new set of management guidelines were implemented including a moratorium on permits, limited days at sea, gear and crew restrictions, and areas closed to fishing. Between 1994 and 2005, the biomass of the U.S. sea scallop population increased by 18-fold on Georges Bank and by 8-fold in the Mid-Atlantic Bight region.[11]
The state of Maine has an inshore (within 3 miles) winter (December - April) scallop fishery that is managed by the Maine Department of Marine Resources.[12] Scallops in Maine inshore waters are harvested by mechanical draggers or by SCUBA divers ("dive caught"). In 2009 low harvest numbers caused the Department of Marine Resources to cut the season short and proposed a series of management measures.[13][14] Entry to the fishery became limited, the season was reduced to 70 days, and the minimum ring size was increased to four inches. Additionally, 13 conservation closures (~20% of coastal Maine waters) were created for the following three fishing seasons.[15] In 2012, the Department of Marine Resources proposed developing a rotational closure system for the fishery, based on a 10-year schedule.[16] This rotational closure system was adopted only in the Zone 2 region of the state fishery. All three zones have different management tools that include limited access areas and in-season targeted closures.[17] Since 2009, both dollar value and landings have gone up for the sea scallop fishery in the state of Maine.[18]
The Monterey Bay Aquarium Seafood Watch lists sea scallops as a "Good Alternative," its second best rating.[19] Greenpeace red listed the Atlantic sea scallop, stating that scallop stocks are being overfished and that the fishing methods used are destroying corals and sponges. According to Greenpeace the fishery of scallops kills nearly 1,000 loggerhead sea turtles every year.[20] Since 2015, chain mats and Turtle Deflector Dredges (TDDs) have been added to offshore equipment to reduce sea turtle deaths.[21] This has caused a significant reduction in sea turtles getting caught in harvesting gear.
Scallop dredge catch Placopecten magellanicus, previously listed as Pecten tenuicostatus and as Pecten grandis and once referred to as the "giant scallop", common names Atlantic deep-sea scallop, deep sea scallop, North Atlantic sea scallop, American sea scallop, Atlantic sea scallop, or sea scallop, is a commercially important pectinid bivalve mollusk native to the northwest Atlantic Ocean.
