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Placopecten magellanicus - A Scallop

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  • Neal Robbins
        These links have photos of Placopecten magellanicus. http://en.wikipedia.org/wiki/File:Placopecten_magellanicus.jpg
    Message 1 of 1 , Apr 1, 2012
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          These links have photos of Placopecten magellanicus.
       
       
          Placopecten magellanicus is often called the Atlantic Scallop. This mollusk is in the class bivalvia, the order Ostreoidea, and the family Pectinidage. Placopecten magellanicus is native to the Atlantic Ocean. Its range extends from North Carolina to Labrador. Placopecten magellanicus lives at depths of 20-200 m. (65.62-656.17 feet). The average depth is about 40 m. (131.23 feet).
          Placopecten magellanicus is 10-23 cm. (3.04-9.06 inches) long. The average length is about 15 cm. (6.91 inches). The shell consists of two valves that are unequal in size. The lower one is nearly flat and the upper valve is convex. There are grooves that radiate from the hinge toward the end of the shell. The upper valve is generally red or pinkish brown. It sometimes has white rays. The lower valve is pinkish white. The interior of the shell is glossy white. It has a muscular scar where the body is attached. The muscle itself has a tan or white coloration. It has two labial or feeding palps; a mouth is located between them. The body of Placopecten magellanicus is wedge-shaped and has a foot on the ventral portion. The ctenidia (gills) are situated in the mantle cavity. A set of eyes are connected to the mantile cavity.
          The eyes of Placopecten magellanicus are typically cobalt blue. They are positioned on the tip of the pallial tentacles. The eyes are complete with lens and cornea, but they cannot distinguish shapes. However, they can detect changes in movement and light.
          The central nervous system of Placopecten magellanicus is relatively simple. There are visceral ganglia near the optic lobes. They fuse with other ganglia and form a simplistic "visceral brain". It comprises most of the nervous system.
          About 40% of the individuals of the species are hermaphrodites. They carry an ovary and a testis inside the mantle cavity. The ovary is bright pink when it carries ripe eggs. The testis is behind the mantle cavity. The ovary and the testis are fused together. They have short ducts that lack glands.
          Breeding occurs in late summer and early autumn. Populations in the Mid-Atlantic region can breed during the spring. Males release their fertilizing chemicals, which enter the food cavity of females. This causes females to release eggs into the mantle. After fertilization, the zygotes are emitted into the water. Placopecten magellanicus reach breeding maturity at about two years of age. However, the eggs are not actively produced until the age of four.
          After fertilization, the young develop into a ciliated larva that is called the trochosphere. Cilia are close to the top. A cilia ring is around the middle. The larvae then grow to the Veliger stage. During this phase they are planktonic larva and cilia feeders. They float in plankton fields for 2-3 months. The larvae continue growing. They start to secrete two valves from the mantle cavity upon reaching adulthood. The average lifespan of Placopecten magellanicus is 6-8 years.
          The diet of Placopecten magellanicus includes microscopic plants, algae, organic particles, and bacteria. The ctenidia and labial cillia are used to collect food. Water comes into the ventral siphon. A current is maintained for passing food through the gill lamellae. It is here that food particles are separated from the sand and mud. The ctenidia send the food particles to the mantle cavity. They circulate over numerous groups of cilia. Those particles become covered with mucus. They are shifted toward the mouth, or the rejection path, which goes through the dorsal siphon. The mucus coated food is transported to the stomach through the esophagus, but it first goes through the crystalline style, which is a gelatinous rotating rod. The food is digested in food vacoules that are intracellular. Waste is expelled through the intestines and out through the anus.
          Starfish and whelks are the main predators of Placopecten magellanicus. Placopecten magellanicus claps it valves together if it sees a predator. It uses a type of jet propulsion to move. A stream of water is forced backwards and out through the hinge and wings. The large muscle powers the locomotion.
          This publication is a reference:
       
      K. Hodges. 2001. "Placopecten magellanicus" (On-line), Animal Diversity Web. Accessed April 01, 2012 at
       
          Neal Robbins
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