Placopecten magellanicus

Geographic Range

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 nearctic
  • native native
• atlantic ocean atlantic ocean
  • native native

Habitat

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.

• Habitat Regions
• temperate temperate
• saltwater or marine saltwater or marine

• Aquatic Biomes
• pelagic pelagic
• coastal coastal

Physical Description

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.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry
• polymorphic polymorphic

Development

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 metamorphosis

Reproduction

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.

• Key Reproductive Features
• year-round breeding year-round breeding
• simultaneous hermaphrodite
• sexual sexual
• fertilization fertilization
  • internal 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

Lifespan/Longevity

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.

Behavior

P. magellanicus is a solitary animal, but can be found in groups of other scallops although this grouping is not intentional. Though scallops do need to be in close proximity for the male to stimulate the female for reproduction. The larva can be sessile, but the adult scallop is mobile and when it is not moving, it is resting on the ocean floor.

• Key Behaviors
• crepuscular crepuscular
• sessile sessile
• motile motile
• sedentary sedentary
• solitary solitary

Communication and Perception

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 visual
• tactile tactile

• Other Communication Modes
• photic/bioluminescent photic/bioluminescent
• pheromones pheromones

• Perception Channels
• visual visual
• tactile tactile
• chemical chemical

Food Habits

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.

• Primary Diet
• herbivore herbivore
  • algivore
• planktivore planktivore
• detritivore detritivore

• Plant Foods
• algae
• phytoplankton phytoplankton

• Other Foods
• detritus detritus
• microbes

• Foraging Behavior
• filter-feeding filter-feeding

Predation

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.

Ecosystem Roles

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.

Economic Importance for Humans: Positive

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 food

Additional Links

Encyclopedia of Life

Contributors

Renee Sherman Mulcrone (editor).

Kathryn Hodges (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.

References

Borradaile, L., Potts. 1963. The Invertebrata: A Manual for the Use of Students . Cambridge: The University Press.

Hart, D. January 2001. "Status of Fisheries Resources off Northeastern United States" (On-line). Accessed 11/04/04 at http://www.wh.whoi.edu/sos/spsyn/iv/scallop/ .

Morris, P. 1951. Field guide to the shells of our Atlantic coast . Boston: Houghton Mifflin.

Morton, J. 1979. Molluscs . London: Hutchinson & Co. Ltd..

Pearse, V., J. Pearse, M. Buchsbaum, R. Buchsbaum. 1987. Living Invertebrata . California: The Bookwood Press.

Pennak, R. 1989. Fresh Water Invertabrates of the United States: Protozoa to Mollusca . New York: John Wiley & Sons, Inc..