Chlamys opercularis

Geographic Range

Chlamys opercularis is a widely distributed bivalve mollusc primarily found along Neogene deposits in the east coast of the North Atlantic Ocean and adjacent seas. Boundaries of its range include northern Norway and the Faroe Islands in the north, south to the Iberian Peninsula, and western Ireland to the west (including the Isle of Man in the United Kingdom) and the Mediterranean and Adriatic Seas to the east. (Barnes, et al., 2009; Hickson, et al., 1999; Román, et al., 1999)


Chlamys opercularis has shown optimal growth during the cooler seasons of late autumn and early winter. This species is primarily found on firm, sandy gravel or mud at depths of more than 100 meters, where the water temperature is cooler. Chlamys opercularis can also be attached to various kinds of algae, Bryozoa, hydroids, and clean shell and general benthic epifauna. The number of individuals of C. opercularis using natural substrata as juvenile habitats has not been quantified. Reports have shown that maerl grounds (areas formed from loose-lying coralline red algae and characterized by high tides and water movements in the photic zone) support large numbers of C. opercularis and are believed to act as a nursery area. However, there is no evidence that individuals of C. opercularis prefer to live on maerl or if maerl is the initial settlement habitat. (Barnes, et al., 2009; Hickson, et al., 1999; Kamenos, et al., 2004; Román, et al., 1999; Schmidt, et al., 2008)

Physical Description

Chlamys opercularis is distinctly left convex (the left valve is more rounded than the right valve). The shells vary in colors and patterns of pigmentation, which can be affected by both environmental and genetic factors. Their shells are also primarily calcitic, making them relatively insusceptible to dissolution and recrystallization. They can grow up to 90 mm in shell height. In general, scallops lack siphons and the anterior adductor muscle. A large and well-developed posterior adductor muscle is used for locomotion. Young individuals often attach to surfaces by byssal threads (silky filaments). Numerous light receptors (eyes) also line the edge of the mantle. (Fay, et al., 1983; Hickson, et al., 1999; Pechenik, 2009; Vause, et al., 2007; Winkler, et al., 2001)

  • Sexual Dimorphism
  • sexes alike


Chlamys opercularis development is influenced by both environmental and inherited factors. Additionally, their life cycle includes the trochophore and veliger larval stages. Generally, development can be described by three phases based on the nature of the energy source and the nature of the locomotion used. The first phase is considered lecithotrophic, a phase in which nutritional requirements for larvae do not extend beyond what is provided within the egg. Lecithotrophic species also have a reduced larval period during which no specific food is consumed. The second and third phases are considered planktotrophic, a phase in which larvae ingest plankton suspended in the water column. The first phase, or embryonic phase, is extremely vulnerable to environmental conditions and requires locomotion to ensure that the early larvae move into the water column. After fertilization occurs, the offspring remain on or near the seabed for a couple of days until developing into trochophore larvae. In the second phase, or dispersal phase, the trocohophore larvae rise to the surface of the water and is transported by water currents into the water column. Eventually, the trochophore larvae become veliger larvae. The third phase occurs when veliger larvae find a suitable substrate to settle on to undergo metamorphosis and juvenile life before becoming adults. (Allen and Pernet, 2007; Cragg, 1991; Pechenik, 2009)


Chlamys opercularis spawn externally, with released sperm fertilizing released eggs. (Cragg, 1991)

Chlamys opercularis is a simultaneous hermaphrodite, containing both a proximal creamy-colored testis and a distal bright red ovary. Sexual maturity occurs at one year. When spawning takes place, sperm are normally released into the environment initially. Fertilization occurs when the eggs are subsequently released and come into contact with the sperm. The release of gametes into the surrounding water usually occurs in the warmer months of spring and summer, but the actual time varies depending on the region and from year to year. (Cragg, 1991)

  • Breeding season
    Chlamys opercularis breeds in the spring and summer.
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

There is no parental protection, however, the eggs provide yolk to sustain the lecithotrophic larvae. (Allen and Pernet, 2007; Cragg, 1991)

  • Parental Investment
  • pre-fertilization
    • provisioning


Chlamys opercularis has a lifespan of 8-10 years. (Schmidt, et al., 2008; Strahl and Abele, 2010)

  • Typical lifespan
    Status: wild
    8 to 10 years


Chlamys opercularis, along with other species in the family Pectinidae and the cephalopods, are the only mollusks that use jet propulsion swimming. Chlamys opercularis swims by creating many rapid valve adductions that expel water from the mantle cavity. The force of the water exiting the organism pushes the individual skyward in the water column. When C. opercularis senses danger or any other kind of disturbance, its swimming escape reflex is triggered. Swimming is an important behavior for this species because it also provides the opportunity to move to a new environment if conditions in the old one become unfavorable. (Jenkins, et al., 2003; Kristmundsson, et al., 2011; Phillipp, et al., 2008; Schmidt, et al., 2008; Shumway and Parsons, 2006)

Communication and Perception

Chlamys opercularis grows on maerl and possibly communicates with it through active molecules gamma aminobutyric acid or other surface properties of the maerl. Responses to stress from potential predation or changes in environment are innate. Because C. opercularis senses danger through disturbance, it detects when fish trawls are approaching. (Kamenos, et al., 2006)

Food Habits

Chlamys opercularis filter feeds. This species was once thought to only consume phytoplankton but recent research indicates zooplankton is also an important source of nutrients. Zooplankton species that C. opercularis consumes include halacarid mites, calanoid copepods, halacarid fragments, copepod fragments, crustacean nauplii, barnacle cyprids, and cladocerans. (Lehane and Davenport, 2002)


Chlamys opercularis is preyed on upon primarily by marine bottom-dwellers, such as Asteria rubens (common starfish), Pagurus spp. (hermit crabs), and Cancer pagurus (brown crab). It is also preyed on by Callionymus lyra (demersal fish). An anti-predator adaptation of this species includes jet propulsion swimming. The predator that has the biggest impact upon C. opercularis populations is humans. Because this organism is considered a delicacy, it is fished in great quantities. (Murray, et al., 2009; Schmidt, et al., 2008)

Ecosystem Roles

Chlamys opercularis has a variety of ecosystem roles. Because it is heavily fished, many undersized animals are thrown back into the water. Small individuals of C. opercularis can sustain shell damage during this process, which makes them especially vulnerable to predation. Starfish (Asteria rubens) will prey upon these individuals. Chlamys opercularis is infected by microsporidians. Little is known about these parasites, except that they are found in the digestive tract of C. opercularis and use the scallop's blood to move around the body. (Kristmundsson, et al., 2011; Murray, et al., 2009)

  • Ecosystem Impact
  • creates habitat
Commensal/Parasitic Species
  • Microsporidians

Economic Importance for Humans: Positive

Chlamys opercularis has a high commercial fishing value. There is a large European market, especially in the United Kingdom and Spain, for fresh C. opercularis. A high demand for C. opercularis is economically important for humans because it not only provides a food source that can be exported for profit, but also creates many jobs. Fisheries and governments are trying to push the industry towards sustainable aquaculture, which could be less destructive to the natural ecosystem, less harmful in discarding undersized scallops, and more environmentally friendly. A more sustainable system could also be more economically viable and ensure a more consistent yield of product. (Murray, et al., 2009; Schmidt, et al., 2008)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

Seafood processing employees can acquire occupational asthma as a result of prolonged exposure to C. opercularis. Processing plants can put strict instructions on how to handle C. opercularis and keep the facilities clean, which may slow productivity or increase costs. (Barraclough, et al., 2006; Jenkins, et al., 2003)

Conservation Status

This species is not listed, but there is a high demand for its harvest. Fisheries and governments are working to a more sustainable aquaculture for this species. (Murray, et al., 2009)

Other Comments

Chlamys opercularis is also called Aequipecten opercularis in the scientific community. Commercially they are known as queen scallops, “queens” or “queenies”. (Barraclough, et al., 2006; Jenkins, et al., 2003; Schmidt, et al., 2008; Shumway and Parsons, 2006)


Alexandra Sarabia (author), The College of New Jersey, Catherine Zymaris (author), The College of New Jersey, Keith Pecor (editor), The College of New Jersey, Renee Mulcrone (editor), Special Projects.


Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map


Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


uses smells or other chemicals to communicate


animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body


union of egg and spermatozoan


a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.


A substance that provides both nutrients and energy to a living thing.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


an animal that mainly eats all kinds of things, including plants and animals


photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)


an animal that mainly eats plankton


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.


remains in the same area


non-motile; permanently attached at the base.

Attached to substratum and moving little or not at all. Synapomorphy of the Anthozoa


reproduction that includes combining the genetic contribution of two individuals, a male and a female


uses touch to communicate


movements of a hard surface that are produced by animals as signals to others


animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)


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